Note 16 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Sales	$ 32,660,531	$ 32,189,623	$ 31,902,027	$ 31,002,746	$ 27,320,481	$ 26,397,857	$ 26,449,885	$ 23,994,004	$ 127,754,927	$ 104,162,227
Gross Profit	7,588,082	6,309,803	6,768,491	6,366,405	4,731,545	5,397,709	5,780,290	6,002,921	27,032,781	21,912,465
Operating Income	2,760,946	1,999,678	2,375,527	1,397,321	676,214	1,868,781	2,119,797	2,325,460	8,533,472	6,990,252
Pretax Income									7,732,194	7,362,942
Net Income	3,069,719	$ 1,254,545	$ 1,171,264	$ 1,065,875	64,699	$ 1,197,877	$ 1,247,305	$ 3,143,417	6,561,403	5,653,298
Capital Expenditures									742,828	3,144,503
Depreciation and Amortization									3,750,805	2,986,599
Identifiable Assets	99,598,074				90,963,311				99,598,074	90,963,311
Corporate, Non-Segment [Member]
Capital Expenditures									154,674	103,143
Depreciation and Amortization									167,155	139,255
Identifiable Assets	2,215,461				5,813,250				2,215,461	5,813,250
Commercial Air Handling [Member]
Sales									47,649,695	38,018,412
Gross Profit									10,751,822	7,749,628
Operating Income									6,670,069	3,065,156
Pretax Income									6,670,069	3,071,119
Net Income									4,769,099	2,303,339
Industrial and Transportation Products [Member]
Sales									80,105,232	66,143,815
Gross Profit									16,280,959	14,162,131
Operating Income									5,955,820	4,519,290
Pretax Income									5,951,335	4,209,308
Net Income									4,253,978	3,468,366
Corporate and Other [Member]
Sales										0
Gross Profit									0	706
Operating Income									(4,092,417)	(594,194)
Pretax Income									(4,889,210)	82,515
Net Income									(2,461,674)	(118,407)
Commercial Air Handling Equipment [Member] | Operating Segments [Member]
Capital Expenditures									53,591	187,941
Depreciation and Amortization									431,752	437,770
Identifiable Assets	20,681,082				17,004,003				20,681,082	17,004,003
Industrial and Transportation Products Segment [Member] | Operating Segments [Member]
Capital Expenditures									534,563	2,853,419
Depreciation and Amortization									3,151,898	2,409,574
Identifiable Assets	$ 76,701,530				$ 68,146,058				$ 76,701,530	$ 68,146,058