Today my boss mentioned a gas leak scare at his home (the service company found a slightly loose exterior fitting that happened to be near a vent in the side of the house), and I took the opportunity to ask whether he was still interested in a gas detector for the trailer at the farm.
Nay. They have a new trailer, and the old one leaks water (as well, presumably, as gas), and they don’t use the old one any more.
So I probably won’t go any further with my flammable gas detector project. But it was still enjoyable figuring out as much as I did.