CO exposure is accumulative. If you’re around an intense source of it you’re toast. But with a small point source or decent ventilation it kills you slower. An

CO exposure is accumulative. If you’re around an intense source of it you’re toast. But with a small point source or decent ventilation it kills you slower. And your body produces new blood cells every day, so minor sources like wood smoke or burning a candle don’t dose you enough to be a problem, unless perhaps your day job is as an athlete.