How to set fire to yourself

So we have a colleague who has a bit of a nervous habit in that he just cannot stop checking his shirt, pants, jacket, hanky etc for loose threads, even when we're all chatting in someone's room (usually mine - it's the cleanest) and then when he finds a loose thread he will filch my lighter or someone else's and just burn it off, right there. It's a little bit unnerving to see someone hold a naked flame to their own shirt just to burn off a tiny little bit of thread no longer than a couple of millimeters, but I guess we all have different ways of amusing ourselves.

Is it just me or does anyone else think that holding a naked flame to a cotton shirt could be a fire hazard? I'm almost completely certain that cotton is flammable. Anyway. Whether he sets himself on fire one day is not really the point - my concern really is that he will do it in my office one day and then the fire could spread to my personal belongings and then where will we be. Or he could be blocking the entrance to my office when he's on fire and then how am I going to flee. Also it will be difficult to get the smell of burning hair out of my clothes. People will notice.

If we ever wanted to play a really evil office trick on him, this would definitely be his Achilles heel. All we need to do is get him a really hot Zegna shirt, soak it in kerosene, let it dry out a little, tease out a couple of threads in front and then gift wrap it.