Not sure if you'all know about this one... but its kinda cool in a geeky kinda way.
I've been putting a lot of CO detectors in the birds I've been restoring. I like the Guardian product.
Back when I did my first restoration in 2008, there really wasnt any basis for this other than a FA. In 2017, the FAA issued what they call the "Non Required Safety Enhancing Equipment" or NORSEE letter. A bit silly? Perhaps... but for those of us who like things neat and tidy and ducks being in a row, its kinda cool.
At any rate, here is one of the Guadians I install: https://www.aircraftspruce.com/catalog/pspages/aero451-201.php
And the NORSEE letter.
https://www.faa.gov/sites/faa.gov/files/aircraft/air_cert/design_approvals/norsee/carbon_monoxide_detector.pdf
https://www.faa.gov/aircraft/air_cert/design_approvals/norsee


