RF remotes generally work this way: The originating signal is sent from the remote as RF (radio frequency.) In the case of the MX-950 in my theater that's 418MHz, a very stable and reliable frequency band.
By nature, propane is clear and contains no scent at all. For safety purposes propane. companies add a substance known as ethyl-mercaptan to the propane fuel. Ethyl-. mercaptan has a strong rotten egg, or skunk-like scent, which allows the consumer to. smell it in the case of a leak.
Sewer gas does not always smell like sewer gas. Check the traps under your basin and/or tub. If they are leaking they are allowing the odor through the traps; or they simply evacuated themselves. I've had situations where a trap leaked under a basin and the resulting mold under the cabinet smelled like methane.