What chemicals in cigarette smoke cause lack of oxygen?

Chemicals? More like poisons! Lets see, theres tar,which makes your lungs black,theres nicotine,a substance that is addictive,sometimes rat poisoning if the guy that made them is a loon, and last tobacco a plant grown on farms. Altogether, it kills or puts in high risk or gives cancer to over 4,000,000,000 people a year. So my advice. "DON'T SMOKE!"