I actually never blew into a tissue to see if brown residue was left... I found that out my second year in college when me and my roommate (we were both heavy smokers and it was also the "party smoker's room" there was pretty much a cigarette lit at all times. When we tore down our posters at the end of the year, we realized the paint had darkened our paint by *at least* 3 shades. LOL, I also used to be able to tell by looking at my nic stained fingers, and a lady I used to smoke with outside, she was the receptionist and we'd go smoke and gossip together, and she'd always joke about her "Hitler 'stash" from smoking cigs (she did indeed have one), so the tar is visible even if you don't see it build up in your lungs.
Oddly, much nic staining on hands disappeared when I switched to additive free tobacco, so I'm not quite sure what that was about. It was still plenty tarry as we used old cans of American spirits as ashtrays-- cut a hole in the top, fill halfway with water, and there you go. I had one sitting out there for a long time as I was quitting and this dreadful black, goopy stuff collected around the bottom and started oozing out of it.... LOL, during the worst of the quitting phase I asked the husband if I could eat it, but he was firmly in the "No, Anna, you may NOT," camp, but it was definitely PURE tar, it looked like what they use to put down new tarmac on the roads....
Also, you could tell the health insurance arena WHATEVER you want, and they aren't going to give a rat's, um, tail. They will test you for nicotine if they feel its indicated, and if you test positive they're going to up your premiums or kick you off.... That's how it works, when various states allow that practice. I really wish they would get on board, but like that's ever going to happen without governmental interference... YOUR health and well being is NOT your health insurance company's priority, trust me. They just want to rid themselves of super users, sadly. This is ONE area where I think some regulation is in order, though I know there are folks that disagree, and they are perfectly entitled to their opinion.
Also, if you tell a life insurance co you are cigarette free, if they test for nicotine and find it, they won't pay out, even if you didn't die of a heart attack, and your lungs are pure as the driven snow. They just won't. It's better to be upfront, while providing as little information as possible. I really don't *like* insurance companies trying to enroll me in wellness programs or otherwise finding out about the state of my health. When I get called to do a "health review" I just politely state that I have my *own* doctors to guide me, and that their job is to PAY said providers to do so, not nanny into my damn health. I may use slightly different words, but I try to use a polite tone... LOL. I just really don't desire to be "coached" by some nurse I don't know.
Anna