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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 KnO8urTwnNwc7+JPmpF+piGP7Egap+VLk3LLzptUksp8OJwHpvjxbR8sIPm7gTZF
 HAtDWvCSB8R1Qb8JeJ8CrA==

<SEC-DOCUMENT>0000922423-05-002026.txt : 20051221
<SEC-HEADER>0000922423-05-002026.hdr.sgml : 20051221
<ACCEPTANCE-DATETIME>20051221110529
ACCESSION NUMBER:		0000922423-05-002026
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051215
FILED AS OF DATE:		20051221
DATE AS OF CHANGE:		20051221

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Flynn Frederick C JR
		CENTRAL INDEX KEY:			0001347297

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-16239
		FILM NUMBER:		051277251

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		203-316-9347

	MAIL ADDRESS:	
		STREET 1:		256 OCEAN DRIVE WEST
		CITY:			STAMFORD
		STATE:			CT
		ZIP:			06902

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ATMI INC
		CENTRAL INDEX KEY:			0001041577
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INORGANIC CHEMICALS [2810]
		IRS NUMBER:				061481060
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		7 COMMERCE DRIVE
		CITY:			DANBURY
		STATE:			CT
		ZIP:			06810-4169
		BUSINESS PHONE:		2037941100

	MAIL ADDRESS:	
		STREET 1:		7 COMMERCE DRVIE
		CITY:			DANBURY
		STATE:			CT
		ZIP:			06810-4169

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ATMI HOLDINGS INC
		DATE OF NAME CHANGE:	19970625
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>kl12045_ex.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2005-12-15</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001041577</issuerCik>
        <issuerName>ATMI INC</issuerName>
        <issuerTradingSymbol>ATMI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001347297</rptOwnerCik>
            <rptOwnerName>Flynn Frederick C JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>256 OCEAN DRIVE WEST</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>STAMFORD</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06902</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Phantom Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>27.54</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-12-15</value>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>53.72</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Phantom Stock Units are to be settled in ATMI Inc. Common Stock upon the separating person's termination as director.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Frederick C. Flynn Jr.</signatureName>
        <signatureDate>2005-12-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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