| Carboxyhemoglobin Levels* | Comments (Symptoms/Signs) |
|---|
| <1% | Healthy nonsmokers (None) | | 2% | Level found in urban exercisers | | 2–4% | May cause subtle effects in some persons with coronary disease | | 3–15% | Typical levels found in light to heavy smokers | | 5% | Typical levels found in people who smoke one pack of cigarettes a day |
|
*Carboxyhemoglobin levels above 10–25% are typically considered potentially significant, that is, capable of causing long-lasting neurological consequences. However, brain injury may occur at higher or lower levels. The significance of carboxyhemoglobin levels in the blood can only be determined by the clinical setting/exposure and physical examination.