Is it legal to smoke in your own plane?
The short answer to "Can I smoke in my own private aircraft?" is "Yes, usually".

As Promised, I looked up the relevant FAR (23.853 - Passenger &amp; Crew Compartment Interiors).  

The actual rule is long and verbose, but pretty common sense. The important regulatory bits for most personal aircraft are just two points though. You must:


Have "an adequate number" of self-contained ash trays
You don't want flicked ash or a snubbed cigarette to start an in-flight fire.
Have "No Smoking" signs you can illuminate, if the passenger/crew compartments are separated
This doesn't apply to most of us since our "personal" airplanes are light singles, but if you've got a fancy twin with a curtain or door between you and the passengers you'll need those signs.


For "commuter category" aircraft there are even more requirements. Those requirements don't apply to most "personal" planes, so even though it's probably a good idea to meet some of those requirements if you're going to allow smoking in your personal aircraft they're not legally required.



All that said, while it's likely legal (unless you've removed your ashtrays or your plane didn't come with them) common sense generally dictates you don't want to smoke in your plane - It's bad for the vacuum-driven instruments' filters, will require even more attention to cleaning the inside of your windows, and a loose cigarette in turbulence or a bunch of ashes blown about by an open air vent can be a pretty substantial distraction.