 One classic sign of carbon monoxide poisoning is more often seen in the dead rather than the living – people have been described as looking red @-@ cheeked and healthy ( see below ) . However , since this " cherry @-@ red " appearance is common only in the deceased , and is unusual in living people , it is not considered a useful diagnostic sign in clinical medicine . In pathological ( autopsy ) examination the ruddy appearance of carbon monoxide poisoning is notable because <unk> dead persons are normally bluish and pale , whereas dead carbon @-@ monoxide poisoned persons may simply appear unusually lifelike in coloration . The colorant effect of carbon monoxide in such postmortem circumstances is thus analogous to its use as a red colorant in the commercial meat @-@ packing industry . 
