Note 13 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Sales	$ 36,933,015	$ 31,902,027	$ 76,417,371	$ 62,904,773
Gross profit	10,474,878	6,768,491	20,991,429	13,134,896
Operating profit	5,152,364	2,375,527	10,271,632	3,772,848
Interest charges	366,101	154,065	735,904	415,081
Unrealized (gain) loss on investments	(177,515)	608,954	(118,482)	434,069
Other (income) expense, net	(345,968)	16,838	(344,971)	(313,063)
Income before Provision for Income Taxes	5,309,746	1,595,670	9,999,181	3,236,761
Operating Segments [Member]
Sales	36,933,015	31,902,027	76,417,371	62,904,773
Gross profit	10,474,878	6,768,491	20,991,429	13,134,896
Operating profit	6,593,302	3,222,187	13,199,599	6,066,517
Corporate and Reconciling Items [Member]
Operating profit	1,440,938	846,660	2,927,967	2,293,669
Commercial Air Handling [Member] | Operating Segments [Member]
Sales	14,860,001	11,845,380	30,911,194	23,403,254
Gross profit	5,029,777	2,453,139	9,469,684	5,082,796
Operating profit	3,987,554	1,382,553	7,402,749	2,944,897
Industrial and Transportation Products [Member] | Operating Segments [Member]
Sales	22,073,014	20,056,647	45,506,177	39,501,519
Gross profit	5,445,101	4,315,352	11,521,745	8,052,100
Operating profit	$ 2,605,748	$ 1,839,634	$ 5,796,850	$ 3,121,620