Only an appropriate detector or instrument can quickly and reliably distinguish between carbon monoxide and carbon dioxide gases. Both gases are colorless, tasteless and odorless.
A functional difference between the two gases is that carbon monoxide is a flammable gas, whereas carbon dioxide is a non-flammable gas, though this difference is not readily noticeable in Earth’s oxygen-rich atmosphere.
Both gases are potentially lethal through inhalation. Symptoms of carbon monoxide poisoning include confusion, nausea, fatigue, fainting, chest pain, abdominal pain and euphoria. Symptoms of carbon dioxide poisoning include nausea, sweating, increased heart rate, frostbite, convulsion, panic and memory problems. Poisoning from either gas results in headaches, dizziness, hallucination and seizures. However, it is extremely difficult to detect either gas through self-diagnosis because both gases result in diminished mental acuity.
Carbon dioxide is a natural by-product of animal respiration. It is also produced in significant quantities by any combustion process, including in engines, stoves, furnaces or fireplaces. Carbon monoxide is also produced by any combustion process, though its concentration is reduced by a catalytic converter.
The safe limit of carbon monoxide is approximately 35 to 50 parts per million. For carbon dioxide, the safe limit is approximately 5,000 parts per million. Fatal poisoning by carbon monoxide is relatively common, whereas poisoning by carbon dioxide is rare.