Thanks for the two about posts. Bruce my does both and Scott not all of us and not me in particular are as experienced as you and I have a good wiffer to but this meter is designed to do just that detect CO and gas isn't that the protocol that I would say I use during my HI's. I guess I can detect gas but I am not that sure I can detect CO and I want to do the job for my client and at least tell them that suspect something is going on. I am still not sure of how this is supposed to be done. Can you guys please be more specfic..