The cheapest thing that saves lives

Any combustion — propane, gasoline, diesel, wood, charcoal — produces carbon monoxide. Colorless, odorless, and it kills people while they sleep, every winter, in vehicles and cabins.

A CO alarm is the highest-value safety purchase in off-grid life. Nothing else on the gear list is close on a dollars-per-risk basis.

The rules:

Never run a generator in or near an enclosed space — including an open garage or beside a window. Portable generators reach lethal CO concentrations shockingly fast.

Never use a charcoal grill or unvented catalytic heater as primary heat in a sleeping space. "Indoor-safe" propane heaters consume oxygen and need a cracked window plus a working alarm. They are not a substitute for a vented system.

Vented diesel and propane furnaces are the safer path — combustion sealed off from your air, exhaust routed outside.

And propane specifically: it's heavier than air, so leaks pool low. Mount the detector low. Tanks outside or in sealed, exterior-vented compartments. Leak-test fittings with soapy water after any work.