Because of its toxicity (and not the exhaustion of oxygen as sometimes thought) CO concentrations of as little as one part per thousand can be fatal if inhaled over a period of two hours.
Karena toksisitasnya (dan bukannya kehabisan oksigen seperti yang terkadang dipikirkan) konsentrasi CO yang bertambah satu banding seribu dapat menjadi fatal jika didiamkan selama dua jam.