I remember reading a fairly in depth article that I cannot find...but some sources I'm able to ID at the moment that discuss the issue:

https://freedom-to-tinker.com/2009/05/11/breathalyzer-source...

https://lawreader.com/?p=12801

https://www.tradesecretslaw.com/2008/02/articles/practice-pr...

https://arstechnica.com/tech-policy/2009/05/buggy-breathalyz...