Note 12 - Segment and Related Information - Information by Industry Segment (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Sales	$ 13,593,192	$ 7,220,626	$ 25,471,892	$ 10,566,941
Income Before Provision for Income Taxes
Income (loss) before provision for income taxes	526,166	978,896	1,024,502	1,200,163
Operating Segments [Member] | Commercial Air Handling [Member]
Sales	10,884,324	3,343,945	20,000,261	3,343,945
Income Before Provision for Income Taxes
Income (loss) before provision for income taxes	1,765,374	607,471	2,630,579	607,471
Operating Segments [Member] | Test and Measurement [Member]
Sales	924,598	2,452,854	1,996,445	4,222,925
Income Before Provision for Income Taxes
Income (loss) before provision for income taxes	(96,172)	343,752	(225,121)	440,885
Operating Segments [Member] | Industrial Hose [Member]
Sales	1,784,270	1,423,827	3,475,186	3,000,071
Income Before Provision for Income Taxes
Income (loss) before provision for income taxes	123,964	27,673	224,153	151,807
Consolidation, Eliminations [Member]
Income Before Provision for Income Taxes
Income (loss) before provision for income taxes	(1,160,574)		(1,160,574)
Corporate, Non-Segment [Member]
Income Before Provision for Income Taxes
Income (loss) before provision for income taxes	$ (106,426)		$ (444,535)