Note 16 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Revenue	$ 33,827,050	$ 33,641,513	$ 36,933,015	$ 39,484,356	$ 32,660,531	$ 32,189,623	$ 31,902,027	$ 31,002,746	$ 143,885,934	$ 127,754,927
Gross Profit	7,745,321	8,909,332	10,474,878	10,516,552	7,588,082	6,309,803	6,768,491	6,366,405	37,646,082	27,032,781
Operating Income	3,363,871	4,296,968	5,152,364	5,119,267	2,760,946	1,999,678	2,375,527	1,397,321	17,932,471	8,533,472
Pretax Income									17,164,148	7,732,194
Net Income	3,237,242	$ 2,814,736	$ 3,851,342	$ 3,391,473	3,069,719	$ 1,254,545	$ 1,171,264	$ 1,065,875	13,294,793	6,561,403
Capital Expenditures									2,032,773	742,828
Depreciation and Amortization									3,921,740	3,750,805
Identifiable Assets	93,639,598				99,598,074				93,639,598	99,598,074
Corporate, Non-Segment [Member]
Capital Expenditures									491,346	154,674
Depreciation and Amortization									144,804	167,155
Identifiable Assets	2,578,598				2,215,461				2,578,598	2,215,461
Commercial Air Handling Equipment [Member] | Operating Segments [Member]
Capital Expenditures									250,685	53,591
Depreciation and Amortization									432,038	431,752
Identifiable Assets	20,252,946				20,681,082				20,252,946	20,681,082
Industrial and Transportation Products Segment [Member] | Operating Segments [Member]
Capital Expenditures									1,290,742	534,563
Depreciation and Amortization									3,344,898	3,151,898
Identifiable Assets	$ 70,808,054				$ 76,701,530				70,808,054	76,701,530
Commercial Air Handling [Member]
Revenue									58,378,593	47,649,695
Gross Profit									19,123,207	10,751,822
Operating Income									15,367,247	6,670,069
Pretax Income									15,367,247	6,670,069
Net Income									10,987,581	4,769,099
Industrial and Transportation Products [Member]
Revenue									85,507,341	80,105,232
Gross Profit									18,522,875	16,280,959
Operating Income									7,594,668	5,955,820
Pretax Income									8,173,742	5,951,335
Net Income									6,090,530	4,253,978
Corporate and Other [Member]
Revenue										0
Gross Profit									0	0
Operating Income									(5,029,444)	(4,092,417)
Pretax Income									(6,376,841)	(4,889,210)
Net Income									$ (3,783,318)	$ (2,461,674)