Note 13 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Sales	$ 39,484,356	$ 31,002,746
Gross Profit	10,516,552	6,366,405
Operating Income	5,119,267	1,397,321
Pretax Income	4,689,435	1,641,091
Net Income	3,391,473	1,065,875
Corporate and Reconciling Items [Member]
Sales		0
Gross Profit	0	0
Operating Income	(1,487,030)	(1,447,008)
Pretax Income	(1,907,964)	(1,337,225)
Net Income	(1,364,194)	(997,435)
Commercial Air Handling [Member] | Operating Segments [Member]
Sales	16,051,193	11,557,874
Gross Profit	4,439,907	2,629,657
Operating Income	3,415,195	1,562,344
Pretax Income	3,415,195	1,562,344
Net Income	2,441,864	1,117,076
Industrial and Transportation Products [Member] | Operating Segments [Member]
Sales	23,433,163	19,444,872
Gross Profit	6,076,645	3,736,748
Operating Income	3,191,102	1,281,985
Pretax Income	3,182,204	1,415,972
Net Income	$ 2,313,803	$ 946,234