The idea of a mechanism to measure the alcohol a person has consumed dates back quite far. A 1927 issue of Popular Science speaks of a device to ‘test a Tippler’s breath’, suggesting that housewives use W.D McNally’s new invention to see if their ‘errant’ husbands had been out drinking. The device is said to use chemicals that change colour, but what chemicals they were is unknown. This is howeverthe same mechanism behind the first portable breathalyzer just years later.
The first stable breathalyzer for out-of-lab use was developed by Rolla N. Harger in 1931 and named, hilariously, the drunkometer. This early breathalyzer functioned very differently from modern ones: it relied on a colour change due to a reaction between alcohol in the breath and acidified potassium permanganate. Lacking a quantitative scale it simply relied on the idea that more purple colour equaledmore alcohol.
The first breathalyzer as we currently know it was developed by Robert Frank Borkenstein in 1958. Borkenstein coupled a photometer with a reaction between the alcohol in a subject’s breath and potassium dichromate.
His breathalyzer was a tremendous leap forward for law enforcement and road safety, as it gave police a non-invasive, quantitative and rapid method to confirm that somebody was too drunk to drive.
Since Borkenstein’s breathalyzer, the technology hasn’t changed that much (read about it here). Except that breathalyzers are now less than $20 and small enough to fit on keychains.