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Meaning, one that would test O2 levels as well as for CO and/or CO2? That would be a big seller, I would think.
As someone interested in buying their first O2 analyzer, a compact combo unit would be a big selling point for me.
BUT baby steps--just getting people to consider that CO could be a problem is huge.
On the other hand, the portable CO devices available to date seem to all require filling a bag and putting the monitor in it, so perhaps that's not feasible.