Supplemental Financial Information Third Quarter 2021 investors.ironmountain.com

Table of Contents Section I - Q3 Earnings Press Release 3 Q3 2021 Earnings Press Release Section II - Company Profile 6 Section III - Financial Highlights Financial and Operating Highlights 7 Organic Revenue Growth 8 Section IV - Operational Metrics Worldwide Storage Volume 9 Quarterly and Year-to-Date Operating Performance 10 Section V - Balance Sheets, Statements of Operations and Reconciliations Condensed Consolidated Balance Sheets 11 Condensed Consolidated Statements of Operations 12 Condensed Consolidated Statements of Operations Year-to-Date 13 Reconciliation of Net Income (Loss) to Adjusted EBITDA 14 Reconciliation of Reported Earnings per Share to Adjusted Earnings per Share 15 Reconciliation of Net Income (Loss) to FFO and AFFO 16 Reconciliation of Net Income (Loss) to FFO and AFFO Year-to-Date 18 Section VI - Storage and Service Reconciliation Storage and Service Business Detail 20 Storage and Service Business Detail Year-to-Date 21 Section VII - Real Estate Metrics 22 Global Real Estate Portfolio and Lease Obligations Facility Lease Expirations Section VIII - Data Center Customer and Portfolio Metrics Data Center Customer Lease Expiration and Leasing Activity Summary 23 Data Center Operating Portfolio 24 Data Center Expansion and Development Activity 25 Section IX - Capitalization and Debt Maturity Profile 26 Capitalization Debt Maturity Profile Section X - Capital Expenditures and Acquisitions Capital Expenditures and Investments 27 Capital Expenditures and Investments Year-to-Date 28 Business and Customer Acquisitions 29 Section XI - Appendix and Definitions 31 All figures except per share, megawatts (MW), kilowatts (kW), and facility counts in 000s unless noted All figures in reported dollars unless noted Figures may not foot due to rounding All figures for the quarter ended September 30, 2021 unless noted Unaudited investors.ironmountain.com Q3 2021 Supplemental Financial Information 2

Iron Mountain Reports Third Quarter Results -- Net Income increases 77%; Achieves record quarterly Revenue, AFFO and Adjusted EBITDA -- BOSTON – November 4, 2021 – Iron Mountain Incorporated (NYSE: IRM), the global leader in innovative storage and information management services, announces financial and operating results for the third quarter of 2021. The conference call / webcast details, earnings call presentation and supplemental financial information, which includes definitions of certain capitalized terms used in this release, are available on Iron Mountain’s Investor Relations website. Reconciliations of non-GAAP measures to the appropriate GAAP measures are included herein. “Our third quarter performance demonstrates the continued strength of the business throughout the year, driven by our broad offerings, deep customer relationships, resilient business model, and strength of our team," said William L. Meaney, president and CEO of Iron Mountain. "Our Mountaineers have been executing well despite what continues to be a challenging environment, and we are pleased to continue to drive accelerated growth with continued strong uptake in our digital and SITAD offerings resulting in 19% year over year growth, strong storage growth of 3.2% with positive organic volume, and continued momentum in our Data Center business, which is well on track to deliver bookings in excess of 30 megawatts for the year." Financial Performance Highlights for the Third Quarter and Year-to-Date 2021 ($ in millions, except per share data) Three Months Ended Year to Date 9/30/21 9/30/20 Y/Y % Change 9/30/21 9/30/20 Y/Y % Change Storage Rental Revenue $719 $696 3% $2,145 $2,057 4% Service Revenue $412 $340 21% $1,187 $1,031 15% Total Revenue $1,130 $1,037 9% $3,332 $3,088 8% Net Income (Loss) $68 $39 77% $391 $96 306% Adjusted EBITDA $418 $376 11% $1,204 $1,101 9% Adjusted EBITDA Margin 37.0% 36.3% +70 bps 36.1% 35.7% +40 bps AFFO $263 $216 22% $745 $697 7% AFFO per share $0.90 $0.75 21% $2.56 $2.42 6% • Total reported Revenues for the third quarter were $1.13 billion, compared with $1.04 billion in the third quarter of 2020, an increase of 9.0%. Excluding the impact of foreign currency exchange (FX), total reported Revenues increased 7.9% compared to the prior year, driven by a 19.7% increase in Service revenue, while Storage rental revenue increased 2.2%. Year to date, total reported Revenues increased 7.9%, or 5.7%, excluding the impact of FX. • Global Data Center business revenue increased 21.7% in the third quarter, or a 21.2% increase compared to the third quarter of 2020, excluding the impact of FX. Through September 30, 2021, Iron Mountain has executed 22 megawatts of new and expansion leasing. Subsequent to the end of the third quarter, the company signed an additional 2 megawatts of new and expansion leases. • Net Income for the third quarter was $68.1 million compared with $38.6 million in the third quarter of 2020. The following items were included in Net Income: ◦ Restructuring Charges of $50.4 million associated with the implementation of Project Summit in the third quarter of 2021 compared to $48.4 million in the third quarter of 2020. ◦ Gain on Disposal/Write-Down of PP&E, Net of $0.9 million in the third quarter of 2021 compared to $75.8 million in the third quarter of 2020, primarily related to the company's capital recycling program. ◦ Other Income, Net of $18.5 million in the third quarter of 2021, primarily related to fluctuations in foreign currency transaction gains, net, compared to Other Expense, Net of $83.5 million in the third quarter of 2020, primarily related to a debt extinguishment charge of $51.3 million. • Year to date, Net Income was $391.3 million, compared with $96.3 million in 2020. The following items were included in Net Income: ◦ Restructuring Charges of $129.7 million compared to $128.7 million year to date 2021 and 2020, respectively. Section I - Q3 Earnings Press Release investors.ironmountain.com Q3 2021 Supplemental Financial Information 3

◦ Intangible Impairment charge of $23.0 million related to the writedown of goodwill associated with the Fine Arts business in the first quarter of 2020. ◦ Gain on Disposal/Write-Down of PP&E, Net of $134.3 million compared to $78.2 million, year to date 2021 and 2020, respectively, primarily related to the company's capital recycling program. ◦ Other Income, Net of $200.0 million year to date 2021, primarily related to a gain on sale from the divestment of the company's Intellectual Property Management business, compared to Other Expense, Net of $66.4 million year to date 2020, primarily related to a debt extinguishment charge of $68.3 million. • Adjusted EBITDA for the third quarter was $417.8 million, compared with $376.0 million in the third quarter of 2020, an increase of 11.1%. On a constant currency basis, Adjusted EBITDA increased by 9.9%, driven by the strong increase in Service revenue, benefits from Project Summit and the flow through from revenue management. Year to date, Adjusted EBITDA was $1.2 billion, compared with $1.1 billion in 2020, an increase of 9.3%. On a constant currency basis, Adjusted EBITDA increased 7.0%. • Reported EPS - Fully Diluted from Net Income (Loss) Attributable to Iron Mountain Incorporated for the third quarter was $0.23, compared with $0.13 in the third quarter of 2020. Year to date, Reported EPS - Fully Diluted from Net Income (Loss) Attributable to Iron Mountain Incorporated was $1.34, compared with $0.33 in 2020. • Adjusted EPS for the third quarter was $0.40, compared with $0.33 in the third quarter of 2020. Adjusted EPS reflects a structural tax rate of 16.5% and 16.3%, in the third quarters of 2021 and 2020, respectively. Year to date, Adjusted EPS was $1.09, compared with $0.88 in 2020. • FFO (Normalized) per share was $0.72 for the third quarter, compared with $0.63 in the third quarter of 2020, an increase of 14.3%. Year to date, FFO (Normalized) per share was $2.03, compared with $1.81 in 2020, an increase of 12.4%. • AFFO was $263.5 million for the third quarter, compared with $216.4 million in the third quarter of 2020, an increase of 21.7%. Year to date, AFFO was $744.9 million, compared with $696.8 million in 2020, an increase of 6.9%. • AFFO per share was $0.90 for the third quarter, compared with $0.75 in the third quarter of 2020, an increase of 20.6%. Year to date, AFFO per share was $2.56, compared with $2.42 in 2020, an increase of 6.1%. Dividend On November 4, 2021, Iron Mountain's board of directors declared a quarterly cash dividend of $0.6185 per share for the fourth quarter. The fourth-quarter 2021 dividend is payable on January 6, 2022, for shareholders of record on December 15, 2021. Guidance Iron Mountain confirmed full-year 2021 guidance; details are summarized in the table below. 2021 Guidance(1) ($ in millions, except per share data) 2021 Guidance Y/Y % Change Total Revenue $4,415 - $4,515 6% - 9% Adjusted EBITDA $1,600 - $1,635 8% - 11% AFFO $970 - $1,005 9% - 13% AFFO Per Share $3.33 - $3.45 8% - 12% (1) Iron Mountain does not provide a reconciliation of non-GAAP measures that it discusses as part of its annual guidance or long term outlook because certain significant information required for such reconciliation is not available without unreasonable efforts or at all, including, most notably, the impact of exchange rates on Iron Mountain’s transactions, loss or gain related to the disposition of real estate and other income or expense. Without this information, Iron Mountain does not believe that a reconciliation would be meaningful. About Iron Mountain Iron Mountain Incorporated (NYSE: IRM) is the global leader in innovative storage and information management services, storing and protecting billions of valued assets, including critical business information, highly sensitive data, and cultural and historical artifacts. Founded in 1951 and trusted by more than 225,000 customers worldwide, Iron Mountain helps customers CLIMB HIGHER™ to transform their businesses. Through a range of services including digital transformation, data centers, secure records storage, information management, secure destruction, and art storage and logistics, Iron Mountain helps businesses bring light to their dark data, enabling customers to unlock value and intelligence from their stored digital and physical assets at speed and with security, while helping them meet their environmental goals. To learn more about Iron Mountain, please visit: www.IronMountain.com and follow @IronMountain on Twitter and LinkedIn. Section I - Q3 Earnings Press Release investors.ironmountain.com Q3 2021 Supplemental Financial Information 4

Safe Harbor Statement Under the Private Securities Litigation Reform Act of 1995: We have made statements in this press release that constitute "forward-looking statements" as that term is defined in the Private Securities Litigation Reform Act of 1995 and other securities laws. These forward-looking statements concern our operations, economic performance, financial condition, goals, beliefs, future growth strategies, investment objectives, plans and current expectations, such as our (1) 2021 guidance as well as our expectations for growth, including growth opportunities and growth rates for revenue by segment, organic revenue, organic volume and other metrics, (2) expectations and assumptions regarding the impact from the COVID-19 pandemic on us and our customers, including on our businesses, financial position, results of operations and cash flows, (3) expected benefits, costs and actions related to, and timing of, Project Summit, (4) expectations as to our capital allocation strategy, including our future investments, leverage ratio, dividend payments and possible funding sources (including real estate monetization) and capital expenditures, (5) expectations regarding the closing of pending acquisitions and investments, and (6) other forward-looking statements related to our business, results of operations and financial condition. These forward-looking statements are subject to various known and unknown risks, uncertainties and other factors, and you should not rely upon them except as statements of our present intentions and of our present expectations, which may or may not occur. When we use words such as "believes," "expects," "anticipates," "estimates," “plans” or similar expressions, we are making forward-looking statements. Although we believe that our forward-looking statements are based on reasonable assumptions, our expected results may not be achieved, and actual results may differ materially from our expectations. In addition, important factors that could cause actual results to differ from expectations include, among others: (i) the severity and duration of the COVID-19 pandemic and its effects on the global economy, including its effects on us, the markets we serve and our customers and the third parties with whom we do business within those markets; (ii) our ability to execute on Project Summit and the potential impacts of Project Summit on our ability to retain and recruit employees; (iii) our ability to remain qualified for taxation as a real estate investment trust for United States federal income tax purposes; (iv) changes in customer preferences and demand for our storage and information management services, including as a result of the shift from paper and tape storage to alternative technologies that require less physical space; (v) our ability or inability to execute our strategic growth plan, including our ability to invest according to plan, incorporate new digital information technologies into our offerings, achieve satisfactory returns on new product offerings, continue our revenue management, expand internationally, complete acquisitions on satisfactory terms, integrate acquired companies efficiently and grow our business through joint ventures; (vi) changes in the amount of our capital expenditures; (vii) our ability to raise debt or equity capital and changes in the cost of our debt; (viii) the costs of complying with, and our ability to comply with, laws, regulations and customer demands, including those relating to data security and privacy issues, as well as fire and safety and environmental standards; (ix) the impact of litigation or disputes that may arise in connection with incidents in which we fail to protect our customers' information or our internal records or information technology systems and the impact of such incidents on our reputation and ability to compete; (x) changes in the price for our storage and information management services relative to the cost of providing such storage and information management services; (xi) changes in the political and economic environments in the countries in which our international subsidiaries operate and changes in the global political climate, particularly as we consolidate operations and move records and data across borders; (xii) our ability to comply with our existing debt obligations and restrictions in our debt instruments; (xiii) the impact of service interruptions or equipment damage and the cost of power on our data center operations; (xiv) the cost or potential liabilities associated with real estate necessary for our business; (xv) failures in our adoption of new IT systems; (xvi) unexpected events, including those from climate change (xvii) other trends in competitive or economic conditions affecting our financial condition or results of operations not presently contemplated; and (xviii) the other risks described in our periodic reports filed with the SEC, including under the caption “Risk Factors” in Part I, Item 1A of our Annual Report. Except as required by law, we undertake no obligation to update any forward-looking statements appearing in this report. Reconciliation of Non-GAAP Measures: Throughout this release, Iron Mountain discusses (1) Adjusted EBITDA, (2) Adjusted Earnings per Share (“Adjusted EPS”), (3) Funds from Operations (“FFO Nareit”), (4) FFO (Normalized), and (5) Adjusted Funds from Operations (“AFFO”). These measures do not conform to accounting principles generally accepted in the United States (“GAAP”). These non-GAAP measures are supplemental metrics designed to enhance our disclosure and to provide additional information that we believe to be important for investors to consider in addition to, but not as a substitute for, other measures of financial performance reported in accordance with GAAP, such as operating income, net income (loss) attributable to Iron Mountain Incorporated or cash flows from operating activities (as determined in accordance with GAAP). The reconciliation of these measures to the appropriate GAAP measure, as required by Regulation G under the Securities Exchange Act of 1934, as amended, and their definitions are included later in this release. Investor Relations Contact: Sarah Barry, 617-237-6597 Manager, Investor Relations sarah.barry@ironmountain.com Section I - Q3 Earnings Press Release investors.ironmountain.com Q3 2021 Supplemental Financial Information 5

Facts and Figures $4.4 Billion Trailing Twelve-Month Revenue 225,000+ Customer Accounts ~25,000 Employees ~1,460 Facilities Worldwide 89 million+ Pieces of Media 740+ million Cubic Feet of Global Storage Volume Revenue and Gross Profit Mix Geographic Revenue Mix 67% 19% 5% 9% North America Europe Latin America Asia Business Revenue Mix 64% 36% Storage Rental Service Business Adjusted Gross Profit Mix 80% 20% Storage Rental Service Product Revenue Mix 60% 11% 8% 4% 7% 9% 1% Records Management Data Management Data Center Adjacent Businesses Global Digital Solutions Secure Shred Consumer Storage RM Revenue by Vertical - Customer Mix North America 16% 2% 8% 12% 6% 3% 3% 1% 50% Healthcare Federal Legal Financial Insurance Life Sciences Energy Business Services Other Section II - Company Profile investors.ironmountain.com Q3 2021 Supplemental Financial Information 6

Financial Highlights Q3 2021 Q2 2021 Q1 2021 Q4 2020 Q3 2020 Storage Rental Revenue $718,614 $718,272 $708,056 $697,294 $696,294 Service Revenue $411,534 $401,484 $373,984 $362,359 $340,353 Total Revenues $1,130,148 $1,119,756 $1,082,040 $1,059,653 $1,036,647 Adjusted EBITDA $417,769 $405,631 $380,565 $374,247 $376,012 Adjusted EBITDA Margin 37.0 % 36.2 % 35.2 % 35.3 % 36.3 % Net Income (Loss) Attributable to Iron Mountain Incorporated $67,683 $275,285 $45,603 $247,411 $38,394 Reported EPS - Fully Diluted $0.23 $0.95 $0.16 $0.86 $0.13 Adjusted EPS $0.40 $0.38 $0.32 $0.29 $0.33 FFO (Normalized) $208,836 $199,963 $181,338 $173,483 $181,660 FFO (Normalized) per Share $0.72 $0.69 $0.63 $0.60 $0.63 AFFO $263,484 $245,992 $235,391 $190,771 $216,420 AFFO per Share $0.90 $0.85 $0.81 $0.66 $0.75 Dividend per Share $0.62 $0.62 $0.62 $0.62 $0.62 TTM AFFO Payout Ratio 76.8 % 80.7 % 80.1 % 80.4 % 76.7 % Weighted Average Common Shares Outstanding - Diluted 291,482 291,079 289,528 289,161 288,811 Net Lease-Adjusted Leverage Ratio 5.4x 5.3x 5.5x 5.3x 5.3x Operating Highlights Q3 2021 Q2 2021 Q1 2021 Q4 2020 Q3 2020 Organic Storage Rental Revenue Growth 2.3 % 2.5 % 1.7 % 1.7 % 2.5 % Organic Service Revenue Growth 17.7 % 25.5 % (4.8) % (12.1) % (13.5) % Total Volume - Storage 744,280 733,086 728,616 726,430 726,649 Storage Facility Capacity Utilization 81.8 % 84.0 % 82.3 % 81.9 % 82.3 % Records Management Retention Rate 94.4 % 94.4 % 94.4 % 93.7 % 94.1 % Storage Revenue / Sq. Ft $7.83 $7.93 $7.88 $7.78 $7.76 Storage NOI / Sq. Ft $6.39 $6.43 $6.33 $6.16 $6.36 Data Center: Leasable Megawatts 156.6 144.7 136.4 129.8 126.3 Leased % - Stabilized 89.4 % 88.4 % 88.5 % 89.0 % 92.1 % Leased % - Total 85.0 % 83.0 % 85.2 % 87.4 % 91.8 % Kilowatts Leased - New/Expansion 8,989 3,610 9,035 7,435 12,303 Churn 3.9 % 1.9 % 2.3 % 3.9 % 1.6 % Number of Facilities 19 15 15 15 15 Number of Markets 16 13 13 13 13 Section III - Financial Highlights investors.ironmountain.com Q3 2021 Supplemental Financial Information 7

Organic Revenue Growth (1) Q3 2021 Q2 2021 YTD 2021 Reported Constant Currency Organic Revenue Reported Constant Currency Organic Revenue Reported Constant Currency Organic Revenue Storage Rental 3.2% 2.2% 2.3% 6.1% 2.7% 2.5% 4.3% 2.2% 2.2% Service 20.9% 19.7% 17.7% 31.5% 26.9% 25.5% 15.2% 12.7% 11.6% Total Revenues 9.0% 7.9% 7.4% 14.0% 10.2% 9.7% 7.9% 5.7% 5.4% Total Organic Revenue Growth 1.3% 1.0% (7.2)% (3.4)% (3.4)% (0.6)% 9.7% 7.4% Q4 2019 Q1 2020 Q2 2020 Q3 2020 Q4 2020 Q1 2021 Q2 2021 Q3 2021 (8.0)% (4.0)% 0.0% 4.0% 8.0% 12.0% Organic Storage Rental Revenue Growth 2.5% 3.0% 2.3% 2.5% 1.7% 1.7% 2.5% 2.3% Q4 2019 Q1 2020 Q2 2020 Q3 2020 Q4 2020 Q1 2021 Q2 2021 Q3 2021 0.0% 2.0% 4.0% 6.0% Organic Service Revenue Growth (0.7)% (2.3)% (23.1)% (13.5)% (12.1)% (4.8)% 25.5% 17.7% Q4 2019 Q1 2020 Q2 2020 Q3 2020 Q4 2020 Q1 2021 Q2 2021 Q3 2021 (30.0)% (20.0)% (10.0)% 0.0% 10.0% 20.0% 30.0% (1) Constant Currency and excluding impact from business acquisitions and divestitures. Section III - Financial Highlights investors.ironmountain.com Q3 2021 Supplemental Financial Information 8

Worldwide Storage Volume Records and Information Management Adjacent Businesses Consumer and Other Q4 2019 Q1 2020 Q2 2020 Q3 2020 Q4 2020 Q1 2021 Q2 2021 Q3 2021 640,000 660,000 680,000 700,000 720,000 740,000 760,000 Q4 2019 Q1 2020 Q2 2020 Q3 2020 Q4 2020 Q1 2021 Q2 2021 Q3 2021 Records and Information Management 694,614 712,388 712,009 711,148 708,981 708,587 710,790 720,069 Adjacent Businesses 5,508 5,938 5,906 6,534 7,077 7,335 7,683 7,961 Consumer and Other 4,096 4,308 6,495 8,967 10,373 12,694 14,613 16,250 Total 704,218 722,634 724,411 726,649 726,430 728,616 733,086 744,280 Business acquisitions during the quarter (1) 514 18,389 3,555 272 — — 5,020 10,743 (1) Business acquisitions volume acquired during the quarter included in total volume. Section IV - Operational Metrics investors.ironmountain.com Q3 2021 Supplemental Financial Information 9

Third Quarter 2021 Y/Y % Change Q3 2021 Q2 2021 Q3 2020 Reported Constant Currency Organic Growth (2) Global RIM Business Storage Rental $621,615 $617,078 $598,949 3.8% 2.7% 1.8% Service 373,962 375,854 322,824 15.8% 14.6% 13.8% Total Revenues $995,577 $992,932 $921,773 8.0% 6.9% 6.0% Adjusted EBITDA $442,798 $430,308 $393,883 Adjusted EBITDA Margin 44.5 % 43.3 % 42.7 % Global Data Center Business Data Center Revenue (1) $88,587 $76,977 $72,814 21.7% 21.2% 21.2% Adjusted EBITDA $35,097 $33,432 $33,359 Adjusted EBITDA Margin 39.6 % 43.4 % 45.8 % Corporate and Other Business Storage Rental $24,588 $29,957 $28,929 (15.0)% (15.5)% 8.7% Service 21,396 19,890 13,131 62.9% 61.9% 29.6% Total Revenues $45,984 $49,847 $42,060 9.3% 8.6% 16.8% Adjusted EBITDA $(60,126) $(58,109) $(51,230) Total Consolidated Storage Rental $718,614 $718,272 $696,294 3.2% 2.2% 2.3% Service $411,534 401,484 340,353 20.9% 19.7% 17.7% Total Revenues $1,130,148 $1,119,756 $1,036,647 9.0% 7.9% 7.4% Adjusted EBITDA $417,769 $405,631 $376,012 Adjusted EBITDA Margin 37.0 % 36.2 % 36.3 % Year to Date 2021 Y/Y % Change YTD 2021 YTD 2020 Reported Constant Currency Organic Growth (2) Global RIM Business Storage Rental $1,849,387 $1,773,364 4.3% 2.1% 1.7% Service 1,106,416 981,930 12.7% 10.3% 10.0% Total Revenues $2,955,803 $2,755,294 7.3% 5.0% 4.6% Adjusted EBITDA $1,281,668 $1,169,671 Adjusted EBITDA Margin 43.4 % 42.5 % Global Data Center Business Data Center Revenue (1) $236,672 $206,939 14.4% 13.0% 13.0% Adjusted EBITDA $98,961 $94,812 Adjusted EBITDA Margin 41.8 % 45.8 % Corporate and Other Business Storage Rental $84,750 $86,610 (2.1)% (3.1)% 5.5% Service 54,719 38,774 41.1% 37.1% 15.2% Total Revenues $139,469 $125,384 11.2% 9.5% 8.8% Adjusted EBITDA $(176,664) $(163,010) Total Consolidated Storage Rental $2,144,942 $2,056,797 4.3% 2.2% 2.2% Service 1,187,002 1,030,820 15.2% 12.7% 11.6% Total Revenues $3,331,944 $3,087,617 7.9% 5.7% 5.4% Adjusted EBITDA $1,203,965 $1,101,473 Adjusted EBITDA Margin 36.1 % 35.7 % (1) Includes Global Data Center service revenue of $16.2M, $5.7M, and $4.4M in Q3 2021, Q2 2021, and Q3 2020, respectively, and $25.9M and $10.1M for YTD 2021 and YTD 2020 respectively. (2) Constant Currency and excluding impact from business acquisitions and divestitures. Section IV - Operational Metrics investors.ironmountain.com Q3 2021 Supplemental Financial Information 10

Condensed Consolidated Balance Sheets 9/30/2021 12/31/2020 ASSETS Current Assets: Cash and Cash Equivalents $161,439 $205,063 Accounts Receivable, Net 884,348 859,344 Prepaid Expenses and Other 223,266 205,380 Total Current Assets $1,269,053 $1,269,787 Property, Plant and Equipment: Property, Plant and Equipment $8,503,171 $8,246,337 Less: Accumulated Depreciation (3,914,553) (3,743,894) Property, Plant and Equipment, Net $4,588,618 $4,502,443 Other Assets, Net: Goodwill $4,472,641 $4,557,609 Customer Relationships, Customer Inducements and Data Center Lease-Based Intangibles 1,230,330 1,326,977 Operating Lease Right-of-Use Assets 2,308,047 2,196,502 Other 365,706 295,949 Total Other Assets, Net $8,376,724 $8,377,037 Total Assets $14,234,395 $14,149,267 LIABILITIES AND EQUITY Current Liabilities: Current Portion of Long-term Debt $318,144 $193,759 Accounts Payable 324,210 359,863 Accrued Expenses and Other Current Liabilities 926,360 1,146,288 Deferred Revenue 257,593 295,785 Total Current Liabilities $1,826,307 $1,995,695 Long-term Debt, Net of Current Portion 8,815,273 8,509,555 Long-term Operating Lease Liabilities, Net of Current Portion 2,164,449 2,044,598 Other Long-term Liabilities 155,048 204,508 Deferred Income Taxes 236,782 198,377 Redeemable Noncontrolling Interests 61,390 59,805 Total Long-term Liabilities $11,432,942 $11,016,843 Total Liabilities $13,259,249 $13,012,538 Equity Total Equity $975,146 $1,136,729 Total Liabilities and Equity $14,234,395 $14,149,267 Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 11

Quarterly Condensed Consolidated Statements of Operations Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change Revenues: Storage Rental $718,614 $718,272 — $696,294 3.2 % Service 411,534 401,484 2.5 % 340,353 20.9 % Total Revenues $1,130,148 $1,119,756 0.9 % $1,036,647 9.0 % Operating Expenses: Cost of Sales (excluding Depreciation and Amortization) $481,663 $474,579 1.5 % $434,505 10.9 % Selling, General and Administrative 241,596 259,779 (7.0) % 232,095 4.1 % Depreciation and Amortization 174,818 166,685 4.9 % 157,252 11.2 % Acquisition and Integration Costs 1,138 2,277 (50.0) % — — Restructuring Charges 50,432 39,443 27.9 % 48,371 4.3 % (Gain) Loss on Disposal/Write-Down of PP&E, Net (935) (128,935) (99.3) % (75,840) (98.8) % Total Operating Expenses $948,712 $813,828 16.6 % $796,383 19.1 % Operating Income (Loss) $181,436 $305,928 (40.7) % $240,264 (24.5) % Interest Expense, Net 103,809 105,220 (1.3) % 104,303 (0.5) % Other (Income) Expense, Net (18,501) (186,230) (90.1) % 83,465 (122.2) % Net Income (Loss) Before Provision (Benefit) for Income Taxes $96,128 $386,938 (75.2) % $52,496 83.1 % Provision (Benefit) for Income Taxes 28,017 110,416 (74.6) % 13,934 101.1 % Net Income (Loss) $68,111 $276,522 (75.4) % $38,562 76.6 % Less: Net Income (Loss) Attributable to Noncontrolling Interests 428 1,237 (65.4) % 168 154.5 % Net Income (Loss) Attributable to Iron Mountain Incorporated $67,683 $275,285 (75.4) % $38,394 76.3 % Net Income (Loss) Per Share Attributable to Iron Mountain Incorporated: Basic $0.23 $0.95 (75.8) % $0.13 76.9 % Diluted $0.23 $0.95 (75.8) % $0.13 76.9 % Weighted Average Common Shares Outstanding - Basic 289,762 289,247 0.2 % 288,403 0.5 % Weighted Average Common Shares Outstanding - Diluted 291,482 291,079 0.1 % 288,811 0.9 % Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 12

Year to Date Condensed Consolidated Statement of Operations YTD 2021 YTD 2020 % Change Revenues: Storage Rental $2,144,942 $2,056,797 4.3 % Service 1,187,002 1,030,820 15.2 % Total Revenues $3,331,944 $3,087,617 7.9 % Operating Expenses: Cost of Sales (excluding Depreciation and Amortization) (1) $1,408,151 $1,308,119 7.6 % Selling, General and Administrative (2) 760,098 712,775 6.6 % Depreciation and Amortization 507,145 483,686 4.8 % Acquisition and Integration Costs 3,415 — — Restructuring Charges 129,686 128,715 0.8 % Intangible Impairments — 23,000 (100.0) % (Gain) Loss on Disposal/Write-Down of PP&E, Net (134,321) (78,170) 71.8 % Total Operating Expenses $2,674,174 $2,578,125 3.7 % Operating Income (Loss) $657,770 $509,492 29.1 % Interest Expense, Net 313,451 313,408 — Other (Income) Expense, Net (200,018) 66,439 (401.1) % Net Income (Loss) Before Provision (Benefit) for Income Taxes $544,337 $129,645 319.9 % Provision (Benefit) for Income Taxes 153,073 33,304 359.6 % Net Income (Loss) $391,264 $96,341 306.1 % Less: Net Income (Loss) Attributable to Noncontrolling Interests 2,693 1,058 154.5 % Net Income (Loss) Attributable to Iron Mountain Incorporated $388,571 $95,283 307.8 % Net Income (Loss) Per Share Attributable to Iron Mountain Incorporated: Basic $1.34 $0.33 306.1 % Diluted $1.34 $0.33 306.1 % Weighted Average Common Shares Outstanding - Basic 289,255 288,105 0.4 % Weighted Average Common Shares Outstanding - Diluted 290,697 288,471 0.8 % (1) Includes $7.6M of direct and incremental costs related to COVID-19 in YTD 2020. (2) Includes $1.6M of direct and incremental costs related to COVID-19 in YTD 2020. Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 13

Quarterly Reconciliation of Net Income (Loss) to Adjusted EBITDA Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change Net Income (Loss) $68,111 $276,522 (75.4) % $38,562 76.6 % Add / (Deduct): Interest Expense, Net 103,809 105,220 (1.3) % 104,303 (0.5) % Provision (Benefit) for Income Taxes 28,017 110,416 (74.6) % 13,934 101.1 % Depreciation and Amortization 174,818 166,685 4.9 % 157,252 11.2 % Acquisition and Integration Costs 1,138 2,277 (50.0) % — — Restructuring Charges 50,432 39,443 27.9 % 48,371 4.3 % (Gain) Loss on Disposal/Write-Down of PP&E, Net (Including Real Estate) (935) (128,935) (99.3) % (75,840) (98.8) % Other (Income) Expense, Net, Excluding our Share of Losses (Gains) from our Unconsolidated Joint Ventures (21,517) (189,605) (88.7) % 81,190 (126.5) % Stock-Based Compensation Expense (1) 12,644 22,536 (43.9) % 8,065 56.8 % Our Share of Adjusted EBITDA Reconciling Items from our Unconsolidated Joint Ventures 1,252 1,072 16.8 % 175 615.0 % Adjusted EBITDA $417,769 $405,631 3.0 % $376,012 11.1 % Year to Date Reconciliation of Net Income (Loss) to Adjusted EBITDA YTD 2021 YTD 2020 % Change Net Income (Loss) $391,264 $96,341 306.1 % Add / (Deduct): Interest Expense, Net 313,451 313,408 — Provision (Benefit) for Income Taxes 153,073 33,304 359.6 % Depreciation and Amortization 507,145 483,686 4.8 % Acquisition and Integration Costs 3,415 — — Restructuring Charges 129,686 128,715 0.8 % Intangible Impairments — 23,000 (100.0) % (Gain) Loss on Disposal/Write-Down of PP&E, Net (Including Real Estate) (134,321) (78,170) 71.8 % Other (Income) Expense, Net, Excluding our Share of Losses (Gains) from our Unconsolidated Joint Ventures (209,001) 59,398 (451.9) % Stock-Based Compensation Expense (1) 45,913 32,056 43.2 % COVID-19 Costs (2) — 9,285 (100.0) % Our Share of Adjusted EBITDA Reconciling Items from our Unconsolidated Joint Ventures 3,340 450 641.4 % Adjusted EBITDA $1,203,965 $1,101,473 9.3 % (1) Stock-based compensation expense related to Project Summit is included within Restructuring Charges for the three and nine months ended September 30, 2021 and 2020. (2) Costs that are incremental and directly attributable to the COVID-19 pandemic which are not expected to recur once the pandemic ends ("COVID-19 Costs"). These costs include the purchase of personal protective equipment for our employees and incremental cleaning costs of our facilities, among other direct costs. Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 14

Quarterly Reconciliation of Reported Earnings per Share to Adjusted Earnings per Share Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change Reported EPS - Fully Diluted from Net Income (Loss) Attributable to Iron Mountain Incorporated $0.23 $0.95 (75.4) % $0.13 78.6 % Add / (Deduct): Acquisition and Integration Costs — 0.01 (50.0) % — — Restructuring Charges 0.17 0.14 27.7 % 0.17 — (Gain) Loss on Disposal/Write-Down of PP&E, Net (Including Real Estate) (0.01) (0.44) (98.8) % (0.26) (98.0) % Other (Income) Expense, Net, Excluding our Share of Losses (Gains) from our Unconsolidated Joint Ventures (0.07) (0.65) (88.7) % 0.28 (126.3) % Stock-Based Compensation Expense 0.04 0.08 (44.0) % 0.03 55.3 % Tax Impact of Reconciling Items and Discrete Tax Items (1) 0.02 0.31 (94.0) % (0.02) (213.3) % Adjusted EPS - Fully Diluted from Net Income (Loss) Attributable to Iron Mountain Incorporated $0.40 $0.38 3.5 % $0.33 20.3 % Year to Date Reconciliation of Reported Earnings per Share to Adjusted Earnings per Share YTD 2021 YTD 2020 % Change Reported EPS - Fully Diluted from Net Income (Loss) Attributable to Iron Mountain Incorporated $1.34 $0.33 305.1 % Add / (Deduct): Acquisition and Integration Costs 0.01 — — Restructuring Charges 0.45 0.45 — Intangible Impairments — 0.08 (100.0) % (Gain) Loss on Disposal/Write-Down of PP&E, Net (Including Real Estate) (0.46) (0.27) 70.5 % Other (Income) Expense, Net, Excluding our Share of Losses (Gains) from our Unconsolidated Joint Ventures (0.72) 0.21 (449.2) % Stock-Based Compensation Expense 0.16 0.11 42.1 % COVID-19 Costs — 0.03 (100.0) % Tax Impact of Reconciling Items and Discrete Tax Items (1) 0.31 (0.06) (657.4) % Income (Loss) Attributable to Noncontrolling Interests 0.01 — — Adjusted EPS - Fully Diluted from Net Income (Loss) Attributable to Iron Mountain Incorporated $1.09 $0.88 23.8 % (1) The difference between our effective tax rates and our structural tax rate (or adjusted effective tax rates) for the quarters ended September 30, 2021 and 2020, is primarily due to (i) the reconciling items above, which impact our reported net income (loss) before provision (benefit) for income taxes and (ii) other discrete tax items. Our structural tax rate for purposes of the calculation of Adjusted EPS for the three and nine months ended September 30, 2021 and 2020 was 16.5% and 16.3%, respectively, and three and six months ended June 30, 2021 was 16.2%. The Tax Impact of Reconciling Items and Discrete Tax Items is calculated using the current quarter’s estimate of the annual structural tax rate for the full year. This may result in the current period adjustment plus prior reported quarterly adjustments not summing to the full year adjustment. Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 15

Quarterly Reconciliation of Net Income (Loss) to FFO and AFFO Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change Net Income $68,111 $276,522 (75.4) % $38,562 76.6 % Add / (Deduct): Real Estate Depreciation (1) 79,463 74,784 6.3 % 72,019 10.3 % Loss (Gain) on Sale of Real Estate, Net of Tax 748 (102,476) (100.7) % (75,880) (101.0) % Data Center Lease-Based Intangible Asset Amortization (2) 10,458 10,482 (0.2) % 10,441 0.2 % FFO (Nareit) $158,780 $259,312 (38.8) % $45,142 251.7 % Add / (Deduct): Acquisition and Integration Costs 1,138 2,277 (50.0) % — — Restructuring Charges 50,432 39,443 27.9 % 48,371 4.3 % (Gain) Loss on Disposal/Write-Down of PP&E, Net (Excluding Real Estate) (1,668) (1,076) 55.0 % 40 (4,227.3) % Other (Income) Expense, Net, Excluding our Share of Losses (Gains) from our Unconsolidated Joint Ventures (21,517) (189,605) (88.7) % 81,190 (126.5) % Stock-Based Compensation Expense 12,644 22,536 (43.9) % 8,065 56.8 % Real Estate Financing Lease Depreciation 3,740 3,515 6.4 % 3,501 6.8 % Tax Impact of Reconciling Items and Discrete Tax Items (3) 5,304 63,570 (91.7) % (4,648) (214.1) % Our Share of FFO (Normalized) Reconciling Items from our Unconsolidated Joint Ventures (17) (9) 85.2 % (1) 1,600.0 % FFO (Normalized) $208,836 $199,963 4.4 % $181,660 15.0 % Per Share Amounts (Fully Diluted Shares): FFO (Nareit) $0.55 $0.89 (38.2) % $0.16 243.8 % FFO (Normalized) $0.72 $0.69 4.3 % $0.63 14.3 % Weighted Average Common Shares Outstanding - Basic 289,762 289,247 0.2 % 288,403 0.5 % Weighted Average Common Shares Outstanding - Diluted 291,482 291,079 0.1 % 288,811 0.9 % (1) Includes depreciation expense related to owned real estate assets (land improvements, buildings, building improvements, leasehold of improvements and racking), excluding depreciation related to real estate financing leases. (2) Includes amortization expense for Data Center In-Place Lease Intangible Assets and Data Center Tenant Relationship Intangible Assets. (3) Represents the tax impact of (i) the reconciling items above, which impact our reported net income (loss) before provision (benefit) for income taxes and (ii) other discrete tax items. Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 16

Quarterly Reconciliation of Net Income (Loss) to FFO and AFFO (Continued) Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change FFO (Normalized) $208,836 $199,963 4.4 % $181,660 15.0 % Add / (Deduct): Non-Real Estate Depreciation 37,128 34,191 8.6 % 32,629 13.8 % Amortization Expense (1) 36,361 36,250 0.3 % 33,271 9.3 % Amortization of Deferred Financing Costs 4,027 4,316 (6.7) % 4,149 (2.9) % Revenue Reduction Associated with Amortization of Permanent Withdrawal Fees and Above - and Below-Market Leases 2,251 2,065 9.0 % 2,363 (4.8) % Non-Cash Rent Expense (Income) 3,722 3,958 (6.0) % 2,779 33.9 % Reconciliation to Normalized Cash Taxes 8,133 188 4,225.9 % (5,107) (259.2) % Our Share of AFFO Reconciling Items from our Unconsolidated Joint Ventures 1,021 969 5.3 % 83 1,131.1 % Less: Recurring Capital Expenditures 37,995 35,909 5.8 % 35,407 7.3 % AFFO $263,484 $245,992 7.1 % $216,420 21.7 % Per Share Amounts (Fully Diluted Shares): AFFO Per Share $0.90 $0.85 7.0 % $0.75 20.6 % Weighted Average Common Shares Outstanding - Basic 289,762 289,247 0.2 % 288,403 0.5 % Weighted Average Common Shares Outstanding - Diluted 291,482 291,079 0.1 % 288,811 0.9 % (1) Includes Customer Relationship Value, intake costs, acquisition of customer relationships, and other intangibles. Excludes amortization of capitalized commissions of $7.7M, $7.5M, and $5.4M in Q3 2021, Q2 2021, and Q3 2020, respectively. Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 17

Year to Date Reconciliation of Net Income (Loss) to FFO and AFFO YTD 2021 YTD 2020 % Change Net Income $391,264 $96,341 306.1 % Add / (Deduct): Real Estate Depreciation (1) 230,294 224,325 2.7 % (Gain) Loss on Sale of Real Estate, Net of Tax (106,033) (77,461) 36.9 % Data Center Lease-Based Intangible Asset Amortization (2) 31,423 32,173 (2.3) % FFO (Nareit) $546,948 $275,378 98.6 % Add / (Deduct): Acquisition and Integration Costs 3,415 — — Restructuring Charges 129,686 128,715 0.8 % Intangible Impairments — 23,000 (100.0) % (Gain) Loss on Disposal/Write-Down of PP&E, Net (Excluding Real Estate) (2,890) (359) 705.3 % Other (Income) Expense, Net, Excluding our Share of Losses (Gains) from our Unconsolidated Joint Ventures (209,001) 59,398 (451.9) % Stock-Based Compensation Expense 45,913 32,056 43.2 % COVID-19 Costs — 9,285 (100.0) % Real Estate Financing Lease Depreciation 10,791 10,095 6.9 % Tax Impact of Reconciling Items and Discrete Tax Items (3) 65,120 (16,464) (495.5) % Our Share of FFO (Normalized) Reconciling Items from our Unconsolidated Joint Ventures (30) (31) (1.6) % FFO (Normalized) $589,952 $521,073 13.2 % Per Share Amounts (Fully Diluted Shares): FFO (Nareit) $1.88 $0.95 97.1 % FFO (Normalized) $2.03 $1.81 12.4 % Weighted Average Common Shares Outstanding - Basic 289,255 288,105 0.4 % Weighted Average Common Shares Outstanding - Diluted 290,697 288,471 0.8 % (1) Includes depreciation expense related to owned real estate assets (land improvements, buildings, building improvements, leasehold of improvements and racking), excluding depreciation related to real estate financing leases. (2) Includes amortization expense for Data Center In-Place Lease Intangible Assets and Data Center Tenant Relationship Intangible Assets. (3) Represents the tax impact of (i) the reconciling items above, which impact our reported net income (loss) before provision (benefit) for income taxes and (ii) other discrete tax items. Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 18

Year to Date Reconciliation of Net Income (Loss) to FFO and AFFO (Continued) YTD 2021 YTD 2020 % Change FFO (Normalized) $589,952 $521,073 13.2 % Add / (Deduct): Non-Real Estate Depreciation 106,185 100,357 5.8 % Amortization Expense (1) 106,097 99,704 6.4 % Amortization of Deferred Financing Costs 12,470 13,150 (5.2) % Revenue Reduction Associated with Amortization of Permanent Withdrawal Fees and Above - and Below-Market Leases 6,578 7,612 (13.6) % Non-Cash Rent Expense (Income) 13,091 8,276 58.2 % Reconciliation to Normalized Cash Taxes 10,080 25,881 (61.1) % Our Share of AFFO Reconciling Items from our Unconsolidated Joint Ventures 2,902 234 1,140.2 % Less: Recurring Capital Expenditures 102,487 79,521 28.9 % AFFO $744,868 $696,766 6.9 % Per Share Amounts (Fully Diluted Shares): AFFO Per Share $2.56 $2.42 6.1 % Weighted Average Common Shares Outstanding - Basic 289,255 288,105 0.4 % Weighted Average Common Shares Outstanding - Diluted 290,697 288,471 0.8 % (1) Includes Customer Relationship Value, intake costs, acquisition of customer relationships, and other intangibles. Excludes amortization of capitalized commissions of $22.4M and $17.0M, in YTD 2021 and 2020, respectively. Section V - Balance Sheets, Statements of Operations and Reconciliations investors.ironmountain.com Q3 2021 Supplemental Financial Information 19

Quarterly Storage Rental and Service Business Detail Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change Storage Rental Business Detail Total Storage Rental Revenue $718,614 $718,272 — $696,294 3.2 % Plus: Terminations/Permanent Withdrawal Fees 5,612 6,926 (19.0) % 5,237 7.3 % Total Revenue from Adjusted Storage Rental Activities $724,225 $725,198 (0.1) % $701,531 3.2 % Less: Storage Rental Expenses Storage Rent 104,513 99,727 4.8 % 90,460 15.5 % Other Facility Costs 87,613 86,711 1.0 % 79,170 10.7 % Storage Rental Labor 7,120 7,559 (5.8) % 6,475 10.0 % Other Storage Rental Expenses 8,206 11,883 (30.8) % 8,034 2.1 % Storage Rental Cost of Sales $207,452 $205,880 0.9 % $184,139 12.7 % Storage Rental Gross Profit $516,773 $519,319 (0.5) % $517,392 (0.1) % Storage Rental Gross Margin 71.4 % 71.6 % (20 bps) 73.8 % (240 bps) Storage Rental Allocated Overhead 35,026 36,908 (5.1) % 36,902 (5.1) % Total Storage Rental Adjusted EBITDA $481,747 $482,411 (0.1) % $480,491 0.3 % Storage Rent 104,513 99,727 4.8 % 90,460 15.5 % Storage Rental Net Operating Income $586,260 $582,138 0.7 % $570,951 2.7 % Service Business Detail Total Service Revenue $411,534 $401,484 2.5 % $340,353 20.9 % Less: Terminations/Permanent Withdrawal Fees 5,612 6,926 (19.0) % 5,237 7.3 % Total Revenue from Adjusted Service Activities $405,922 $394,559 2.9 % $335,115 21.1 % Less: Service Expenses Service Rent 2,838 2,868 (1.2) % 3,203 (11.4) % Other Facility Costs 7,508 6,792 10.5 % 6,200 21.1 % Service Labor 183,165 191,524 (4.4) % 177,403 3.2 % Other Service Expenses 80,699 67,514 19.5 % 63,561 27.0 % Service Cost of Sales $274,211 $268,699 2.1 % $250,367 9.5 % Service Gross Profit $131,712 $125,860 4.6 % $84,748 55.4 % Service Gross Margin 32.4 % 31.9 % 50 bps 25.3 % 710 bps Service Allocated Overhead 23,900 22,489 6.3 % 20,830 14.7 % Total Service Adjusted EBITDA $107,812 $103,370 4.3 % $63,919 68.7 % Section VI - Storage and Service Reconciliation investors.ironmountain.com Q3 2021 Supplemental Financial Information 20

Year to Date Storage Rental And Service Business Detail YTD 2021 YTD 2020 % Change Storage Rental Business Detail Total Storage Rental Revenue $2,144,942 $2,056,797 4.3 % Plus: Terminations/Permanent Withdrawal Fees 19,490 15,261 27.7 % Total Revenue from Adjusted Storage Rental Activities $2,164,432 $2,072,058 4.5 % Less: Storage Rental Expenses Storage Rent $301,529 $269,339 12.0 % Other Facility Costs 262,273 240,003 9.3 % Storage Rental Labor 21,932 18,174 20.7 % Other Storage Rental Expenses 30,936 29,191 6.0 % Storage Rental Cost of Sales $616,671 $556,707 10.8 % Storage Rental Gross Profit $1,547,761 $1,515,351 2.1 % Storage Rental Gross Margin 71.5 % 73.1 % (160 bps) Storage Rental Allocated Overhead 112,224 118,358 (5.2) % Total Storage Rental Adjusted EBITDA $1,435,522 $1,396,994 2.8 % Storage Rent 301,529 269,339 12.0 % Storage Rental Net Operating Income $1,737,066 $1,666,333 4.2 % Service Business Detail Total Service Revenue $1,187,002 $1,030,820 15.2 % Less: Terminations/Permanent Withdrawal Fees 19,490 15,261 27.7 % Total Revenue from Adjusted Service Activities $1,167,512 $1,015,559 15.0 % Less: Service Expenses Service Rent $8,891 $9,322 (4.6) % Other Facility Costs 20,760 18,518 12.1 % Service Labor 556,833 534,221 4.2 % Other Service Expenses 204,996 181,703 12.8 % Service Cost of Sales $791,480 $743,765 6.4 % Service Gross Profit $376,032 $271,794 38.4 % Service Gross Margin 32.2 % 26.8 % 540 bps Service Allocated Overhead 72,452 68,368 6.0 % Total Service Adjusted EBITDA $303,580 $203,428 49.2 % Section VI - Storage and Service Reconciliation investors.ironmountain.com Q3 2021 Supplemental Financial Information 21

Global Real Estate Portfolio and Lease Obligations Global Real Estate Portfolio (1) Owned Facilities Leased Facilities (2) Total Buildings Sq. Ft. Buildings Sq. Ft. Buildings Sq. Ft. Total as of 6/30/2021 (3) 269 24,696 1,183 69,048 1,452 93,744 Additions & Expansions 5 803 26 1,168 31 1,971 Dispositions & Move Outs (1) (33) (18) (731) (19) (764) Total as of 9/30/2021 (4) 273 25,465 1,191 69,486 1,464 94,951 Total % 18.6 % 26.8 % 81.4 % 73.2 % Top Five Markets Owned, United States (in Sq. Ft.) Top Five Markets Owned, International (in Sq. Ft.) Northern New Jersey 1,966 Paris, France 807 Chicago 1,282 Montreal, Canada 552 Boston 1,258 Mexico City, Mexico 452 Dallas 966 Toronto, Canada 434 Houston 917 Lima, Peru 434 Facility Lease Expirations (5) (% of total square feet subject to lease) 3.9% 6.0% 4.5% 4.3% 5.3% 2.8% 2.8% 3.4% 5.2% 4.7% 57.1% 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 Thereafter Weighted-Average Remaining Operating Lease Obligation: 11.2 Years (1) Includes real estate held in consolidated joint ventures. (2) Out of the 26 leased building additions and expansions, 20 were the result of acquiring leases in business acquisitions and leased buildings related to acquisitions of customer relationships. (3) Reflects adjustments to previous periods due to refinements to real estate basis. (4) Includes 11 owned data center facilities and 5 leased data center facilities with 2.7M Sq.Ft. and 0.6M Sq. Ft., respectively. (5) Includes financing and operating lease obligations. Section VII - Real Estate Metrics investors.ironmountain.com Q3 2021 Supplemental Financial Information 22

Data Center Customer Lease Expiration Year Number of Leases Expiring Total MW Expiring Percentage of Total MW Annualized GAAP TCV Rent Expiring Percentage of TCV Annualized Rent 2021 95 2.0 1.4% $7,423 2.4% 2022 580 18.9 12.9% 57,682 18.9% 2023 303 18.8 12.8% 55,170 18.1% 2024 215 10.7 7.3% 28,465 9.3% 2025 55 13.8 9.4% 32,918 10.8% 2026 57 22.3 15.2% 38,756 12.7% 2027 5 1.0 0.6% 1,288 0.4% Thereafter 25 59.2 40.3% 83,064 27.3% Total 1,335 146.8 100.0% $304,766 100.0% WALE: 4.0 years Data Center Leasing Activity Summary Q3 2021 YTD 2021 Transaction Count GAAP MRR kW $ / kW / Month Transaction Count GAAP MRR kW $ / kW / Month New/expansion leases signed 32 $940 8,989 $105 138 $2,623 21,634 $121 Commenced leases 26 353 2,466 143 128 1,519 9,053 168 Renewed leases 100 869 3,444 252 323 2,925 11,222 261 Churn 3.9% 8.1% Cash Mark to Market (1.3)% (0.4)% GAAP Mark to Market 6.1% 2.3% LON-2 Data Center Rendering (London, UK) Section VIII - Data Center Customer and Portfolio Metrics investors.ironmountain.com Q3 2021 Supplemental Financial Information 23

Data Center Operating Portfolio Stabilized Pre-Stabilized Total Leaseable MW Leased % by MW Leaseable MW Leased % by MW Leaseable MW Leased % by MW Boyers and Other WPA-1 and Other 14.2 77.2 % — — 14.2 77.2 % Phoenix AZP-1 41.0 96.4 % — — 41.0 96.4 % AZP-2 12.0 100.0 % — — 12.0 100.0 % AZS-1 5.7 50.3 % — — 5.7 50.3 % Total Phoenix 58.7 92.6 % — — 58.7 92.6 % Denver DEN-1 11.3 57.8 % — — 11.3 57.8 % New Jersey NJE-1 15.1 100.0 % 1.2 — 16.3 92.6 % Northern Virginia VA-1 12.4 100.0 % — — 12.4 100.0 % VA-2 4.0 100.0 % 6.0 59.0 % 10.0 75.4 % Amsterdam AMS-1 12.7 88.7 % 1.1 40.9 % 13.8 84.9 % London LON-1 5.1 88.4 % 4.0 4.3 % 9.1 51.2 % Frankfurt FRA-2 2.4 100.0 % — — 2.4 100.0 % Singapore SIN-1 6.9 100.0 % — — 6.9 100.0 % India Web Werks JV 1.5 37.7 % — — 1.5 37.7 % Total Data Center Properties 144.3 89.4 % 12.3 33.8 % 156.6 85.0 % Total Potential Capacity - Megawatts Q3 2021 Q3 2020 Leasable 156.6 126.3 Under Construction 60.4 48.5 Held for Development 261.6 201.2 Total Data Center Portfolio 478.6 376.0 Section VIII - Data Center Customer and Portfolio Metrics investors.ironmountain.com Q3 2021 Supplemental Financial Information 24

Data Center Expansion and Development Activity Project / Facilities MW Under Construction MW Pre- leased % Pre- Leased Investment in Q3 2021 ($M) Cumulative Investment ($M) Total Expected Investment ($M) Expected Completion Expected Stabilization MW Held for Development Data Center Expansion Amsterdam AMS-1 Phase 4 5.0 — — $0.8 $5.6 $45.0 Q4 2022 Q4 2023 4.6 Frankfurt FRA-2 — — — — — — 8.2 India (1) Web Werks JV 1.2 — — — — — 1.9 Northern Virginia VA-2 — — — — — — 20.0 Phoenix AZP-2 Phase 2 6.0 6.0 100.0% $17.5 $29.6 $36.5 Q4 2021 Q4 2021 — AZP-2 Phase 4 4.0 4.0 100.0% $12.1 $15.3 $26.6 Q4 2021 Q4 2021 — AZP-2 Phase 5 7.0 1.0 14.3% $14.0 $19.0 $100.0 Q3 2022 Q4 2022 19.0 All Other Facilities 23.6 Total Expansion 23.2 11.0 47.5% $44.4 $69.5 $208.1 77.3 New Development Amsterdam AMS-2 — — — — — — 10.6 Chicago CHI-2 — — — — — — 36.0 Frankfurt (2) FRA-1 Phase 1 9.0 9.0 100.0% — — — Q4 2021 Q4 2021 — FRA-1 Phase 2 18.0 18.0 100.0% — — — Q3 2022 Q3 2022 — India (1) Web Werks JV 1.2 — — — — — 16.8 London LON-2 9.0 — — $1.9 $8.1 $70.7 Q4 2022 Q4 2023 18.0 Northern Virginia VA Future Phases — — — — — — 103.0 Total New Development 37.2 27.0 72.6% $1.9 $8.1 $70.7 184.4 Total Development 60.4 38.0 62.9% $46.2 $77.6 $278.8 261.6 (1) Represents an unconsolidated joint venture in India; operating three facilities in three markets. (2) FRA-1 is an unconsolidated joint venture; construction costs are funded by the Joint Venture with Iron Mountain managing the construction. Section VIII - Data Center Customer and Portfolio Metrics investors.ironmountain.com Q3 2021 Supplemental Financial Information 25

Capitalization Senior Credit Facility Capacity $1,956,250 Outstanding $516,250 Letters of Credit $3,064 Remaining Capacity $1,436,936 Interest Rate Spread (Prime) 0.75 % Interest Rate Spread (LIBOR) 1.75 % Weighted Average Interest Rate 1.83 % Maturity Date 6/3/2023 Net Lease-Adjusted Leverage Ratio 5.4x Total Market Capitalization as of 9/30/2021 # of Shares Outstanding 289,546 Share Price as of 09/30/21 $43.45 Total Market Capitalization $12,580,780 Net Debt (1) $9,054,599 Total Enterprise Value $21,635,379 Net Debt to Total Enterprise Value 41.9 % Adjusted EBITDA to Interest Expense 4.0x Credit Facility Fixed Charge Coverage Ratio 2.3x Bond Fixed Charge Coverage Ratio 3.3x Total Enterprise Value to Adjusted EBITDA (2) 13.7x Fixed vs. Floating Rate Debt 83% 17% Fixed Rate Debt Floating Rate Debt Credit Rating S&P Moody's Corporate BB- Ba3 Senior Credit Facility BB Ba3 Outlook Negative Stable Latest Update 5/24/2021 7/2/2021 Total Debt Weighted Average Rates Weighted Average Interest 4.5 % Weighted Average Maturity 6.7 Years USD denominated 81.7 % Debt Maturity Profile ($ in Millions) (3) $30 $248 $973 $31 $545 $696 $1,000 $1,325 $1,000 $1,300 $1,100 $600 Senior Secured Credit Facility Bi-Lateral Loans AUD Term Loan B A/R Securitization USD Term Loan B Mortgage Securitization Senior Unsecured Notes 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 (1) Net debt is calculated as current portion of long-term debt of $318.1M plus long-term debt net of current portion of $8,815.3M plus deferred financing costs of $82.6M less cash and cash equivalents of $161.4M. (2) Total Enterprise Value to Adjusted EBITDA is calculated on a trailing twelve-month basis. (3) Excludes Deferred Financing Costs, Financing Leases, Notes Payable and Other. Section IX - Capitalization and Debt Maturity Profile investors.ironmountain.com Q3 2021 Supplemental Financial Information 26

Quarterly Capital Expenditures Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change Growth: Data Center $72,651 $77,556 (6.3) % $59,861 21.4 % Real Estate 21,033 19,808 6.2 % 17,264 21.8 % Innovation and Other 6,302 2,894 117.8 % 3,163 99.2 % Total Growth Capital Expenditures $99,986 $100,257 (0.3) % $80,288 24.5 % Recurring: Real Estate $13,587 $16,588 (18.1) % $10,948 24.1 % Non-Real Estate 20,497 17,390 17.9 % 20,624 (0.6) % Data Center 3,912 1,931 102.6 % 3,836 2.0 % Total Recurring Capital Expenditures $37,995 $35,909 5.8 % $35,407 7.3 % Total Growth and Recurring Capital Expenditures $137,981 $136,166 1.3 % $115,695 19.3 % Net Change in Prepaid and Accrued Capital Expenditures (14,591) 13,892 (205.0) % (7,387) 97.5 % Total Cash Paid for Growth and Recurring Capital Expenditures $123,390 $150,058 (17.8) % $108,308 13.9 % Section X - Capital Expenditures and Acquisitions investors.ironmountain.com Q3 2021 Supplemental Financial Information 27

Year to Date Capital Expenditures YTD 2021 YTD 2020 % Change Growth: Data Center $209,097 $151,692 37.8 % Real Estate 60,558 45,888 32.0 % Innovation and Other 15,445 5,670 172.4 % Total Growth Capital Expenditures $285,100 $203,250 40.3 % Recurring: Real Estate $43,398 $28,242 53.7 % Non-Real Estate 52,153 43,196 20.7 % Data Center 6,936 8,083 (14.2) % Total Recurring Capital Expenditures $102,487 $79,521 28.9 % Total Growth and Recurring Capital Expenditures $387,587 $282,771 37.1 % Net Change in Prepaid and Accrued Capital Expenditures 31,389 26,391 18.9 % Total Cash Paid for Growth and Recurring Capital Expenditures $418,976 $309,162 35.5 % TTM Recurring Capex as a % of Revenue (excl. Data Center) 3.1% 3.3% 3.5% 3.7% 3.7% Q3 2020 Q4 2020 Q1 2021 Q2 2021 Q3 2021 TTM Data Center Recurring CapEx as a % of Data Center Revenue 4.5% 5.7% 5.5% 5.0% 4.8% Q3 2020 Q4 2020 Q1 2021 Q2 2021 Q3 2021 Section X - Capital Expenditures and Acquisitions investors.ironmountain.com Q3 2021 Supplemental Financial Information 28

Quarterly Business Acquisitions Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change Business Acquisitions Business Acquisitions $174,199 $49,993 248.4 % — — Change in Business Acquisition Accruals and Cash Acquired (6,170) (14,270) (56.8) % 69 (9,042.0) % Total Cash Paid for Acquisitions, Net of Cash Acquired $168,029 $35,723 370.4 % $69 243,420.3 % Year to Date Business Acquisitions YTD 2021 YTD 2020 % Change Business Acquisitions Business Acquisitions $224,192 $118,496 89.2 % Change in Business Acquisition Accruals and Cash Acquired (20,440) 85 (24,147.1) % Total Cash Paid for Acquisitions, Net of Cash Acquired $203,752 $118,581 71.8 % Section X - Capital Expenditures and Acquisitions investors.ironmountain.com Q3 2021 Supplemental Financial Information 29

Quarterly Customer Acquisitions Q3 2021 Q2 2021 Q/Q % Change Q3 2020 Y/Y % Change Customer Acquisitions Acquisition of Customer Relationships $2,747 $2,053 33.8 % $644 326.6 % Customer Inducements 1,330 2,361 (43.7) % 1,299 2.4 % Contract Fulfillment Costs 14,676 12,304 19.3 % 11,968 22.6 % Total Acquisition of Customer Relationships, Customer Inducements, and Contract Fulfillment Costs $18,753 $16,718 12.2 % $13,911 34.8 % Change in Customer Acquisition Accruals (1,588) 714 (322.4) % (1) 158,700.0 % Total Cash Paid for Acquisition of Customer Relationships, Customer Inducements, and Contract Fulfillment Costs $17,165 $17,432 (1.5) % $13,910 23.4 % Year to Date Customer Acquisitions YTD 2021 YTD 2020 % Change Customer Acquisitions Acquisition of Customer Relationships $4,800 $3,529 36.0 % Customer Inducements 5,148 8,269 (37.7) % Contract Fulfillment Costs 43,699 30,706 42.3 % Total Acquisition of Customer Relationships, Customer Inducements, and Contract Fulfillment Costs $53,647 $42,503 26.2 % Change in Customer Acquisition Accruals — — — Total Cash Paid for Acquisition of Customer Relationships, Customer Inducements, and Contract Fulfillment Costs $53,647 $42,503 26.2 % Section X - Capital Expenditures and Acquisitions investors.ironmountain.com Q3 2021 Supplemental Financial Information 30

Non-GAAP Measures and Definitions Non-GAAP measures are supplemental metrics designed to enhance our disclosures and to provide additional information that we believe to be important for investors to consider when evaluating our financial performance. These non-GAAP measures should be considered in addition to, but not as a substitute for, other measures of financial performance reported in accordance with accounting principles generally accepted in the United States of America (“GAAP”), such as operating income, income (loss) from continuing operations, net income (loss) or cash flows from operating activities from continuing operations (as determined in accordance with GAAP). Acquisition and Integration Costs: Acquisition and Integration Costs represent operating expenditures directly associated with the closing and integration activities of our business acquisitions that have closed, or are highly probable of closing, and include (i) advisory, legal and professional fees to complete business acquisitions and (ii) costs to integrate acquired businesses into our existing operations, including move, severance, facility upgrade and system integration costs (collectively, "Acquisition and Integration Costs"). Acquisition and Integration Costs do not include costs associated with the formation of joint ventures or costs associated with the acquisition of customer relationships. Adjusted Earnings Per Share, or Adjusted EPS: We define Adjusted EPS as reported earnings per share fully diluted from net income (loss) attributable to Iron Mountain Incorporated (inclusive of our share of adjusted losses (gains) from our unconsolidated joint ventures) and excluding certain items, specifically: (i) Acquisition and Integration Costs; (ii) Restructuring Charges; (iii) Intangible impairments; (iv) (Gain) loss on disposal/write-down of property, plant and equipment, net (including real estate); (v) Other (income) expense, net; (vi) Stock-based compensation expense; (vii) COVID-19 Costs; and (viii) Tax impact of reconciling items and discrete tax items. We do not believe these excluded items to be indicative of our ongoing operating results, and they are not considered when we are forecasting our future results. We believe Adjusted EPS is of value to our current and potential investors when comparing our results from past, present and future periods. Adjusted EBITDA and Adjusted EBITDA Margin: We define Adjusted EBITDA as net income (loss) before interest expense, net, provision (benefit) for income taxes, depreciation and amortization (inclusive of our share of Adjusted EBITDA from our unconsolidated joint ventures), and excluding certain items we do not believe to be indicative of our core operating results, specifically: (i) Acquisition and Integration Costs; (ii) Restructuring Charges; (iii) Intangible impairments; (iv) (Gain) loss on disposal/write-down of property, plant and equipment, net (including real estate); (v) Other (income) expense, net; (vi) Stock-based compensation expense; and (vii) COVID-19 Costs. Adjusted EBITDA Margin is calculated by dividing Adjusted EBITDA by total revenues. We also show Adjusted EBITDA and Adjusted EBITDA Margin for each of our reportable operating segments under “Results of Operations – Segment Analysis” in the 10-Q. We use multiples of current or projected Adjusted EBITDA in conjunction with our discounted cash flow models to determine our estimated overall enterprise valuation and to evaluate acquisition targets. We believe Adjusted EBITDA and Adjusted EBITDA Margin provide our current and potential investors with relevant and useful information regarding our ability to generate cash flows to support business investment. These measures are an integral part of the internal reporting system we use to assess and evaluate the operating performance of our business. Adjusted EBITDA excludes both interest expense, net and the provision (benefit) for income taxes. These expenses are associated with our capitalization and tax structures, which we do not consider when evaluating the operating profitability of our core operations. Adjusted EBITDA also does not include depreciation and amortization expenses, in order to eliminate the impact of capital investments, which we evaluate by comparing capital expenditures to incremental revenue generated and as a percentage of total revenues. Adjusted EBITDA and Adjusted EBITDA Margin should be considered in addition to, but not as a substitute for, other measures of financial performance reported in accordance with accounting principles generally accepted in the United States of America (“GAAP”), such as operating income, net income (loss) or cash flows from operating activities (as determined in accordance with GAAP). Adjusted Funds From Operations, or AFFO: AFFO is defined as FFO (Normalized) (1) excluding (i) non-cash rent expense (income), (ii) depreciation on non-real estate assets, (iii) amortization expense associated with customer relationship value (CRV), intake costs, acquisitions of customer relationships and other intangibles, (other than capitalized internal commissions), (iv) amortization of deferred financing costs and debt discount/premium, (v) revenue reduction associated with amortization of permanent withdrawal fees and above-and below-market data center leases, and (vi) the impact of reconciling to normalized cash taxes, and (2) including recurring capital expenditures. We also adjust for these items to the extent attributable to our portion of unconsolidated ventures. We believe that AFFO, as a widely recognized measure of operations of REITs, is helpful to investors as a meaningful supplemental comparative performance measure to other REITs, including on a per share basis. AFFO should be considered in addition to, but not as a substitute for, other measures of financial performance reported in accordance with GAAP, such as operating income, net income (loss) or cash flows from operating activities (as determined in accordance with GAAP). AFFO per share: AFFO divided by weighted-average fully-diluted shares outstanding Funds From Operations, or FFO (Nareit), and FFO (Normalized): Funds from operations (“FFO”) is defined by the National Association of Real Estate Investment Trusts (“Nareit”) as net income (loss) excluding depreciation on real estate assets, losses and gains on sale of real estate, net of tax, and amortization of data center leased-based intangibles and adjusting for our share of reconciling items from our unconsolidated joint ventures from FFO (“FFO (Nareit)”). FFO (Nareit) does not give effect to real estate depreciation because these amounts are computed, under GAAP, to allocate the cost of a property over its useful life. Because values for well-maintained real estate assets have historically increased or decreased based upon prevailing market conditions, we believe that FFO (Nareit) provides investors with a clearer view of our operating performance. Our most directly comparable GAAP measure to FFO (Nareit) is net income (loss). Although Nareit has published a definition of FFO, we modify FFO (Nareit), as is common among REITs seeking to provide financial measures that most meaningfully reflect their particular business ("FFO (Normalized)"). Our definition of FFO (Normalized) excludes certain items included in FFO (Nareit) that we believe are not indicative of our core operating results, specifically: (i) Acquisition and Integration Costs; (ii) Restructuring Charges; (iii) Intangible impairments; (iv) (Gain) loss on disposal/write-down of property, plant and equipment, net (excluding real estate); (v) Other (income) expense, net; (vi) Stock-based compensation expense; (vii) COVID-19 Costs; (viii) Real estate financing lease depreciation; and (ix) Tax impact of reconciling items and discrete tax items. Section XI - Appendix and Definitions investors.ironmountain.com Q3 2021 Supplemental Financial Information 31

FFO (Normalized) per share: FFO (Normalized) divided by weighted-average fully-diluted shares outstanding. Service Adjusted EBITDA: Service Adjusted EBITDA is calculated by taking service revenues excluding terminations and permanent withdrawals less direct expenses and overhead allocated to the service business. Terminations and permanent withdrawals are excluded from this calculation as they are included in the Storage NOI calculation. Storage Adjusted EBITDA: Storage Adjusted EBITDA is calculated by taking storage revenues including terminations and permanent withdrawal fees less direct expenses and overhead allocated to the storage business. Other Definitions Business Segments Global Record and Information Management ("Global RIM") Business: Provides (i) storage of physical records and healthcare information services, vital records services, courier operations, and the collection, handling and disposal of sensitive documents (collectively, “Records Management”) for customers in 63 countries around the globe, (ii) storage and rotation of backup computer media as part of corporate disaster recovery plans, including service and courier operations (“Data Protection & Recovery”); server and computer backup services; and related services offerings, (collectively, “Data Management”), (iii) Global Digital Solutions (“GDS”), which develops, implements and supports comprehensive storage and information management solutions for the complete lifecycle of our customers’ information, including the management of physical records, conversion of documents to digital formats and digital storage of information, primarily in the United States and Canada, (iv) Secure Shredding, which includes the scheduled pick-up of office records that customers accumulate in specially designed secure containers we provide and is a natural extension of our hardcopy records management operations, completing the lifecycle of a record. Complementary to our shredding operations is the sale of the resultant waste paper to third-party recyclers. Through a combination of shredding facilities and mobile shredding units consisting of custom-built trucks, we are able to offer secure shredding services to our customers throughout the United States, Canada and South Africa, and (v) on-demand, valet storage for consumers (“Consumer Storage”) across 31 markets in North America through a strategic partnership (the “MakeSpace JV”) with MakeSpace Labs, Inc., a consumer storage provider (“MakeSpace”), formed in March 2019. The MakeSpace JV utilizes data analytics and machine learning to provide effective customer acquisition and a convenient and seamless consumer storage experience. Global Data Center Business: Provides enterprise-class data center facilities and hyperscale-ready capacity to protect mission-critical assets and ensure the continued operation of our customers’ IT infrastructure, with secure, reliable and flexible data center options. The world’s most heavily regulated organizations have trusted us with their data centers for over 15 years, and five of the top 10 global cloud providers were Iron Mountain Data Center customers. Our Global Data Center Business footprint spans nine markets in the United States: Denver, Colorado; Kansas City, Missouri; Boston, Massachusetts; Boyers, Pennsylvania; Manassas, Virginia; Edison, New Jersey; Columbus, Ohio; and Phoenix and Scottsdale, Arizona and seven international markets: Amsterdam, London, Singapore and, through unconsolidated joint ventures, Frankfurt, Mumbai, Pune and Noida. Corporate and Other Business: Consists primarily of Adjacent Businesses and other corporate items. Adjacent Businesses is comprised of (i) entertainment and media which helps industry clients store, safeguard and deliver physical media of all types, and provides digital content repository systems that house, distribute, and archive key media assets, throughout the United States, Canada, France, China - Hong Kong S.A.R., and the United Kingdom (“Entertainment Services”) and (ii) technical expertise in the handling, installation and storing of art in the United States, Canada and Europe (“Fine Arts”). Our Corporate and Other Business segment also includes costs related to executive and staff functions, including finance, human resources and IT, which benefit the enterprise as a whole. Capital Expenditures and Investments: Our business requires capital expenditures to support our expected storage rental revenue and service revenue growth and ongoing operations, new products and services and increased profitability. The majority of our capital goes to support business line growth and our ongoing operations. Additionally, we invest capital to acquire or construct real estate. We also expend capital to support the development and improvement of products and services and projects designed to increase our profitability. These expenditures are generally relatively small and discretionary in nature. We categorize our capital expenditures as follows: Growth Investment: Data Center - Expenditures primarily related to investments in new construction of data center facilities (including the acquisition of land and development of facilities) or capacity expansion in existing buildings. Real Estate - Expenditures primarily related to investments in land, buildings, building improvements, leasehold improvements and racking structures to grow our revenues or achieve operational efficiencies. Innovation & Other - Discretionary capital expenditures for significant new products and services, restructuring (including Project Summit), and integration of acquisitions. Section XI - Appendix and Definitions investors.ironmountain.com Q3 2021 Supplemental Financial Information 32

Recurring: Real Estate - Expenditures primarily related to the replacement of components of real estate assets such as buildings, building improvements, leasehold improvements and racking structures. Non-Real Estate - Expenditures primarily related to the replacement of containers and shred bins, warehouse equipment, fixtures, computer hardware, or third-party or internally-developed software assets that support the maintenance of existing revenues or avoidance of an increase in costs. Data Center - Expenditures related to the upgrade or re-configuration of existing data center assets. During 2020, a portion of what was previously categorized as Non-Real Estate Growth Capital Expenditures was recategorized as Real Estate Growth Capital Expenditures and the remaining portion was recategorized as Recurring Capital Expenditures. In addition, capital expenditures associated with restructuring (including Project Summit) and integration of acquisitions, which was previously categorized as recurring capital expenditures, have been recategorized as Innovation and Other. We have reclassified the categorization of our prior year capital expenditures to conform with our current presentation. Components of Overhead: Allocated Overhead – Includes overhead expenses directly associated with storage and service business operations allocated as follows: Field Operation Costs – Allocated to storage and service operations based on percent of revenue. Bad Debt Expenses – Allocated to storage and service operations based on percent of revenue. Transportation Costs – Allocated fully to service operations. Constant Currency: Adjusts results for normalized FX impacts in prior period. COVID-19 Costs: Costs that are incremental and directly attributable to the COVID-19 pandemic which are not expected to reoccur once the pandemic ends ("COVID-19 Costs"). These costs include the purchase of personal protective equipment for our employees and incremental cleaning costs of our facilities, among other direct costs. Bond Fixed Charge Coverage Ratio: Calculated as TTM Adjusted EBITDA divided by scheduled amortization, interest expense related to outstanding debt. Customer Inducements: Represents Free Move Costs and Permanent Withdrawal Fees. Data Center Business Definitions Leasable MW - Represents the amount of critical power capacity available for customer use, measured in megawatts. Leased % Calculation - Calculated as the megawatts under contract divided by the leasable megawatts. Monthly Recurring Revenue (MRR) - defined as recurring contractual revenue under existing commenced customer leases, including rent, power, and other recurring data center services. Pre-leased - A lease on data center capacity that is signed before construction has completed. Pre-Stabilized - A building recently placed in service which has not yet reached 85% leased or 24 months in service. Rental Churn Rate - represents data center leases which are not renewed or are terminated during the period. Rental churn is calculated based on the MRR terminated in the period, compared with total MRR at the beginning of the period. TCV - “Total Contract Value” represents total revenue contracted for active contracts through the contract term, not including renewals or extensions, but including fixed power charges. Total potential MW - Total amount of existing and planned critical power capacity at full build-out, measured in megawatts. WALE - “Weighted Average Lease Expiry” (in years) is calculated on a revenue basis, using annual GAAP revenue of all in-place contracts, excluding utility reimbursements. Credit Facility Fixed Charge Coverage Ratio: Calculated as LTM Adjusted EBITDA plus rent expenses divided by scheduled amortization, interest expense related to outstanding debt and preferred equity, if any, and rent expenses. Net Lease-Adjusted Leverage Ratio: Calculated as net debt including the capitalized value of lease obligations plus six times rent expenses divided by EBITDA plus rent expenses. Organic Revenue Growth: Our organic revenue growth rate, which is a non-GAAP measure, represents the year-over-year growth rate of our revenues excluding the impact of business acquisitions, divestitures and foreign currency exchange rate fluctuations. Our organic revenue growth rates includes the impact of acquisitions of customer relationships. Records Management Retention Rate: One minus the result of dividing the total number of cubic feet of records removed from inventory due to customer terminations and destructions in a one-year period by the total number of cubic feet of records in storage at the beginning of the period. Restructuring Charges: Operating expenditures associated with Project Summit, our transformation program announced in Q4 2019 which is designed to accelerate execution of Iron Mountain's Strategy. Storage Rev/NOI per Sq.Ft.: Storage revenue (or storage NOI) divided by the quarterly building sq ft average for storage products. Section XI - Appendix and Definitions investors.ironmountain.com Q3 2021 Supplemental Financial Information 33

Service Profit and Margin: The Gross Profit and Margin attributable to the worldwide service business. Calculated as follows: Services Adjusted EBITDA + Allocated Overhead Expenses = Service Profit ($) / Total Service Revenues (including Termination and Permanent Withdrawal Fees) = Service Margin (%) Storage Net Operating Income, or Storage NOI: Storage NOI is defined as revenue from rental activities (storage rental revenue, termination fees and permanent withdrawal fees) less storage rental costs. Storage rental costs include facility costs (excluding rent), storage rental labor, other storage costs and allocated overhead. Storage NOI is commonly used in the REIT industry and enables investors to understand and value the income generated from the company’s real estate. Storage Profit and Margin: Gross Profit and Margin attributable to the worldwide storage business. Calculated as follows: Storage Net Operating Income + Allocated Overhead Expenses - Storage Rent = Storage Profit ($) / Total Storage Revenues (excluding Termination and Permanent Withdrawal Fees) = Storage Margin (%) Tax Rates: Effective Tax Rate - GAAP tax rate for the period calculated as tax expense or benefit for the quarter (total of current and deferred tax provisions), including discrete items, and divided by profit before tax for the period. Structural Tax Rate - Estimated tax rate for the full fiscal year based on forecasted ordinary income and forecasted tax expense/benefit excluding any significant unusual or infrequently occurring items (i.e., discrete items) and items recognized net of tax on the financials (i.e., discontinued operations). Total Physical Storage Volume: Iron Mountain’s comprehensive portfolio of physical storage, including Records Management hardcopy records, data protection tapes, Consumer and Other, and Adjacent Businesses (Fine Art and Entertainment Services), measured on an absolute basis in cubic feet. Section XI - Appendix and Definitions investors.ironmountain.com Q3 2021 Supplemental Financial Information 34