Note 16 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023
Revenue	$ 37,386,329	$ 36,736,228	$ 37,636,088	$ 38,439,639	$ 33,827,050	$ 33,641,513	$ 36,933,015	$ 39,484,356	$ 150,198,284	$ 143,885,934
Gross Profit	10,302,098	10,687,649	10,411,315	10,245,033	7,745,321	8,909,332	10,474,878	10,516,552	41,646,095	37,646,082
Operating Income	4,742,665	5,258,441	5,116,181	4,574,090	3,363,871	4,296,968	5,152,364	5,119,267	19,691,377	17,932,471
Pretax Income									17,645,215	17,164,148
Net Income	3,948,415	$ 3,369,211	$ 3,283,456	$ 2,996,885	3,237,242	$ 2,814,736	$ 3,851,342	$ 3,391,473	13,597,967	13,294,793
Capital Expenditures									2,204,527	2,032,773
Depreciation and Amortization									4,156,361	3,921,740
Identifiable Assets	108,668,696				93,639,598				108,668,696	93,639,598
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]
Capital Expenditures									1,152,962	491,346
Depreciation and Amortization									192,576	144,804
Identifiable Assets	8,611,595				2,578,598				8,611,595	2,578,598
Commercial Air Handling Equipment [Member] | Operating Segments [Member]
Capital Expenditures									215,418	250,685
Depreciation and Amortization									289,923	432,038
Identifiable Assets	21,666,328				20,252,946				21,666,328	20,252,946
Industrial and Transportation Products Segment [Member] | Operating Segments [Member]
Capital Expenditures									836,147	1,290,742
Depreciation and Amortization									3,673,862	3,344,898
Identifiable Assets	$ 78,390,773				$ 70,808,054				78,390,773	70,808,054
Commercial Air Handling [Member]
Revenue									65,968,679	58,378,593
Gross Profit									23,860,609	19,123,207
Operating Income									19,646,183	15,367,247
Pretax Income									19,646,183	15,367,247
Net Income									14,047,021	10,987,581
Industrial and Transportation Products [Member]
Revenue									84,229,605	85,507,341
Gross Profit									17,785,486	18,522,875
Operating Income									5,088,181	7,594,668
Pretax Income									5,027,695	8,173,742
Net Income									3,674,941	6,090,530
Corporate Segment and Other Operating Segment [Member]
Revenue										0
Gross Profit									0	0
Operating Income									(5,042,987)	(5,029,444)
Pretax Income									(7,028,663)	(6,376,841)
Net Income									$ (4,123,995)	$ (3,783,318)