Unless you have your own scuba cylinder compressor, you probably don't know for sure what is in your dive tank. Bad air fills have been hitting the headlines recently, and @DiversAlertNetwork are here to offer some solid advice to keep you safe.
you mentioned a CO analyzer for breathing gas that was not too expensive. Where can I look that up? Looking at analyzing my air on holidays to far off places.
There is the TEMC De-Ox CO analyser – https://www.temc.it/en/de-ox-safe-carbon-monoxide-analyzer/