Carbon monoxide poisoning is produced by the incomplete combustion of carbon containing fuels such as gas, coal, oil, wood and coke. Headache is the most common symptom (90%) followed by nausea & vomitting, vertigo, alteration in consciousness and weakness. The cherry red skin colour occurs when COHb concentration exceeds

20% but it is rarely seen in life. Pulse oximetry gives falsely high oxygen saturation sand it is not recommended.