I'm tired of smelling second hand smoke. Any tips or advice you can give to my situation?

Tell them what you said in the question, that you’re at home and that’s completely different. It should be common sense for people to take their smoking habit outside and not in the house, as smoke settles into objects and the ceiling and makes the smell and overall environment even worse. If you can try explaining what you just explained, about the lung cancer as well. People with smoking addictions can be oblivious believe it or not, and some just need the right push to control their habit in front of others even when they have full knowledge theyre destroying their insides. Try breathing through a towel or a medical mask, as this can better filter the air. Maybe line your door with paper towels to the sides and rolled up towel or draft blocker on the bottom. This may not get rid of the smoke in your room when if happens, but it could help, and breathing with a barrier will help so you don’t get your lungs clogged. Maybe find someone else to live with? This seems like you have a lot of experience in this household and in case things still don’t change, maybe try finding another option. To get rid of smoke residue the best you can, wash what’s in your room and clean surfaces that look like they have ash on them if the smoke ever settled in your room. This will get rid of the smell as well as making certain things look cleaner if the smoke settled on them. Maybe try family therapy for your mom if you would like. Also bring this up to a doctor and get checked to make sure this didn’t affect you permenately, and maybe go more than once depending on how this effected you and of course, what your doctor says. Lungs aren’t something to take lightly, so definitely see a doctor. I hope this helps and good luck.