carbon monoxide

The point isn't to scare people about accidental carbon monoxide poisoning, which kills, on average, 374 people per year. Given our population of 319 million, that's a minor threat. Instead, this is to show that the chaotic stuff that makes the nightly newscasts is far less likely to kill you than boring, everyday things.      
Despite 50,000 emergency visits for carbon monoxide poisoning each year in the U.S., there is no effective way to treat it. That could change, thanks to some very clever work being done at the University of Pittsburgh School of Medicine.
Some fatalities from the Northeast's blizzard have taken place inside cars, caused by carbon monoxide poisoning. Although CO makes up only a small fraction of car exhaust -- about 1 percent vs. 70 percent nitrogen -- it's far more dangerous. In fact, carbon monoxide actually "steals" oxygen from your blood.
Smoking but not vaping (using an e-cigarette) was found to impair coronary circulation and raise carbon monoxide (CO) levels