 As many symptoms of carbon monoxide poisoning also occur with many other types of poisonings and infections ( such as the flu ) , the diagnosis is often difficult . A history of potential carbon monoxide exposure , such as being exposed to a residential fire , may suggest poisoning , but the diagnosis is confirmed by measuring the levels of carbon monoxide in the blood . This can be determined by measuring the amount of carboxyhemoglobin compared to the amount of hemoglobin in the blood . 
