The symptoms of carbon monoxide poisoning are important to be able to recognize. If you suspect that you or someone else are experiencing sickness as the result of exposure to carbon monoxide, get to a well-ventilated area immediately and contact emergency services. Symptoms of mild carbon exposure can include: slight headache, nausea, vomiting, fatigue, flu-like symptoms. Symptoms of medium carbon monoxide exposure can include: throbbing headache, drowsiness, confusion, fast heart rate. Symptoms of high exposure to carbon monoxide can include: convulsions, unconsciousness, heart and lung failure. Exposure can lead to brain damage and death.