Neighbors having a bbq is also good for some CO intake.
There's another way to get alerted of CO leaving your compressor. I used a metal filter housing like the one shown below, but without the filter cartridge. Instead, I filled the housing with hopcalite and placed it on the feed line going from the compressor to the airbanks.
View attachment 698799
When CO is present in the air intake, it goes through the compressor and then enters this filter housing. The hopcalite will start turning CO into CO2 and while doing that, it gets hot. Since the hopcalite touches the metal housing, the housing will warm up as well.
The cheapest (and first) detection is done with a $0.30 temperature sensor that is sensitive enough to measure a 0.1 degree difference.
A processing unit can keep track of temperature rise per timeframe and shutdown the compressor in case the increase is too much.
The second detection is done by letting some air pass through a needle valve / flow limiter and direct it over a ZE07-CO sensor ($10-$15). The same unit reading the temperature can also read the CO sensor and shutdown the compressor in case of 1ppm CO detection.
My experience that in such situations, the temperature alerts me of CO presence in the ambient air, but the hopcalite is doing exactly what it needs to do and no CO passes that filter (but I still shut down the compressor and wait until the neighbors are done).