Note 13 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Sales	$ 33,641,513	$ 32,189,623	$ 110,058,884	$ 95,094,396
Gross profit	8,909,332	6,309,803	29,900,761	19,444,700
Operating profit	4,296,968	1,999,678	14,568,600	5,772,527
Interest charges	294,825	331,156	1,030,729	746,237
(Gain) loss on investments	135,522	101,370	17,040	535,439
Other (income) expense, net	(599)	(195,046)	(345,569)	(508,108)
Income before Provision for Income Taxes	3,867,220	1,762,198	13,866,400	4,998,959
Operating Segments [Member]
Sales	33,641,513	32,189,623	110,058,884	95,094,396
Gross profit	8,909,332	6,309,803	29,900,761	19,444,700
Operating profit	5,287,544	2,655,304	18,487,144	8,721,822
Corporate and Reconciling Items [Member]
Operating profit	990,576	655,626	3,918,544	2,949,295
Commercial Air Handling [Member] | Operating Segments [Member]
Sales	12,728,949	11,485,339	43,640,142	34,888,594
Gross profit	4,303,355	2,558,998	13,773,039	7,641,794
Operating profit	3,339,289	1,522,819	10,742,038	4,467,716
Industrial and Transportation Products [Member] | Operating Segments [Member]
Sales	20,912,564	20,704,284	66,418,742	60,205,802
Gross profit	4,605,977	3,750,805	16,127,722	11,802,906
Operating profit	$ 1,948,255	$ 1,132,485	$ 7,745,106	$ 4,254,106