I got in a taxi cab the other day and I was slightly winded because I was carrying heavy bags and had to run a bit to catch the taxi. It was an old car. Usually this doesn't bother me. The first thing I noticed when I got in was a strong scent of burning incense, which I used to enjoy a few years ago, but now avoid due to it's toxicity. After about a minute in the car, I realized there was no burning incense in the car, it was just a fragrance. Then I noticed the heat was on, the driver was a frail guy, dressed in thick clothes, it was obvious the mild temperature outside was too cold for him. Then I realized that it must be the heat that was giving out the incense fragrance. I was still trying to catch my breath, but it felt like no matter how much air I rushed into my lungs, there was no oxygen in there. I rolled down both the back windows and almost had to stick my head out to be able to get a small amount of fresh air. In retrospect, I should've gotten out of that taxi and found another one right then, but I didn't. At one point I started to think that the heating might even be leaking exhaust gases back into the car or something, because it was truly horrible, I felt like I could barely breathe. Well I could breathe just fine, but I felt like that air was not oxygenating me in any way. My blood pressure dropped somewhat and my head was spinning a little bit. I can't say to what extent this was caused by the incense fragrance, but regular incense never caused this effect on me, or anything even remotely like it.