A few weeks ago, the chief operating officer decided to work on a defective waste water gate valve. This involved disconnecting things that are to odorous to discuss in polite company.
Ever since then, there has been a very bad smell in poor 'Old Blue'. Well, everything is buttoned up now but the smell is still there.
I thought it might be gas, not the human kind, but the propane kind, but all seems to be shut off properly, furnace, hot water heater, stove all do not fire up. But smell is there. Put three batteries in the 'carbon monoxide' detector located at eye level and about five feet from aforementioned apparatus and the thing went off like crazy. Question is, 'Where does carbon monoxide come from when there is only human stuff around?'. Old Blue is not running, but the detector is going wild.
Old Humbo

Is there any sort of furnace in the same area as the Barth or is the unit outside. Carbon monoxide is the result of poorly ventilated combustion but it is not something you smell.

Is your propane tank shut off at the tank?
My mind jumps track here because everything you mention that can normally generate carbon monoxide in the unit you have shut off (hot water, furnace, stove, refrig (??).

Tom Taylor

As Tom says, carbon monoxide (CO) is odorless. A CO detector is not totally a precise device, ie there are other gases, some harmful some not, which may be triggering it.

Either way, something is not being vented well! My biggest venting problems have been due to dead animals (squirrels) or animal debris (acorns, again squirrels) getting into the vent pipes.

Might try running a snake through the vents.

Did I mention I hate squirrels?

Well, it seems that the 'old man' put the batteries in the carbon monoxide detector the wrong way, which made it go off and stay screaming. Looked at the manual--fixed that.
But the nose is better than usual. The problem was that after fixing the black water tank valve and reconnecting everything, we didn't put water in the bowl of the toilet so the fumes just came right through. Put the water in, turned the fan on, everything ok now. Think I'm getting senile.