Definition Normal individuals will have up to 3% CO, and smokers may have up to 9%. Patients are generally asymptomatic if < 10%, with overt signs developing at ~ 15%. Carboxyhemoglobin Level Symptoms 1-3% Normal nonsmoker 4-9% Smokers 15-20% Overt signs of toxicity (headache, nausea and vomiting, etc.) 20-25% Signs of severe toxicity (seizures, acute […]