Note 13 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Sales	$ 31,002,746	$ 23,994,004
Gross Profit	6,366,405	6,002,921
Operating Income	1,397,321	2,325,460
Pretax Income	1,641,091	3,668,959
Net Income	1,065,875	3,143,417	$ 5,653,298
Commercial Air Handling [Member]
Sales	11,557,874	8,765,099
Gross Profit	2,629,657	2,230,821
Operating Income	1,562,344	1,045,631
Pretax Income	1,562,344	1,045,631
Net Income	1,117,076	784,224
Industrial and Transportation Products [Member]
Sales	19,444,872	15,228,905
Gross Profit	3,736,748	3,772,100
Operating Income	1,281,985	1,751,443
Pretax Income	1,415,972	3,025,970
Net Income	946,234	2,660,019
Corporate and Other [Member]
Sales		0
Gross Profit	0	0
Operating Income	(1,447,008)	(471,614)
Pretax Income	(1,337,225)	(402,642)
Net Income	$ (997,435)	$ (300,826)