Exposure usually continues for many days, months, years.
A damaging effect of CO poisoning, or in fact, any change which persists, should be referred to as a residual effect. Mucous membranes of the body will almost never be cherry pink. Patients may occasionally present with polycythemia, increased hematocrit, etc. See Characteristics . Chronic CO poisoning is, in fact, difficult to diagnose by those not skilled in its presentation.