Carbon monoxide (CO) poisoning

In the past, using car exhaust fumes to commit suicide was a well known method. Whether that was by running a car engine continuously in an enclosed space like a garage, or by running a pipe from the exhaust directly into the car, again, ideally in a garage. But that was before the days of emission controls on cars, which now emit much lower levels of CO than previously. Whilst it is possible to achieve death using this method, it does generally require older cars. The method is susceptible to a number of things that can go wrong, and for this reason it is no longer cited as an effective method of committing suicide, and certainly not in places like the US, UK and Australia where car emissions are more tightly controlled.

However, CO can be highly toxic if the concentration is high enough. It is also odourless and tasteless and will cause reasonably swift unconsciousness leading to a peaceful and painless death, although there may be some brief panic knowing that the body is not breathing in air. On discovery, the body will look peaceful.

The method relies on being in an enclosed space and generating a high concentration of CO. Purchasing a tank of carbon monoxide is one way of doing this, used with a gas regulator or valve, or with a gas mask.

The enclosed space could be a sealed tent or motor vehicle, with Stone1 estimating a time to death of between 5 to 15 minutes. It does not matter if there is air in the enclosed space to start with, as given a choice between carbon monoxide and oxygen, the protein haemoglobin in the blood will always latch on to carbon monoxide and ignore the life-giving oxygen.

In the Peaceful Pill Handbook2, Nitschke lists estimated times to death depending on the concentration of CO, and recommends concentrations of at least 1% (10,000 ppm), which should achieve death in one to three minutes. For this reason he recommends a reliable CO meter is purchased that is capable of measuring concentrations of at least 1%.

In many countries purchasing a tank of CO is difficult though. Another method of generating carbon monoxide is to use a charcoal grill or hibachi, again within something like tent or a car. Ideally getting the grill burning well before bringing it in to the enclosed space. Do not use this method within a building due to the fire risk and the CO danger to other people. Further information on this method is detailed on the Alt Suicide Holiday website3.

In the Peaceful Pill Handbook2, Nitschke details a method of creating a reaction chamber which generates high concentrations of CO by dripping 85% formic acid into concentrated (98%) sulphuric acid. It is claimed this chamber can achieve peaceful death within a matter of minutes if used in an enclosed space like a car, as the CO generated from the device has been measured as in excess of 3%, with levels exceeding 1% in around 6 minutes.

Whilst seemingly very effective, it should be noted that creating a CO generator does require some skill and dexterity, so this method may not suit many people. It also requires purchasing the formic and sulphuric acid, although these should not be difficult to obtain online. Anyone attempting to use this method will find more information in the Peaceful Pill Handbook2.

CO can cause explosions, so it is essential that there are no exposed electrical wires or light filaments nearby, or anything else that could explode from the gas.

It should also be noted that CO can easily cause damage to other people, so anyone using this method should ensure there is no danger to others, ideally by placing a warning sign outside whatever enclosed space is used to contain the CO.

Once again, the health risks of being interrupted during this method are serious, and can include memory defects and Parkinsonism, as well as dementia, psychosis, paralysis and blindness. So it is essential to ensure there will be no interruptions if using this method. And anyone seriously considering this method may want to read Help me first.

This method probably has few advantages over using helium (see Plastic bag & gas) although it can be effective without the need for using a gas mask or plastic bag over the head, which may outweigh the greater complexity of using CO.


  1. Geo Stone, Suicide and Attempted Suicide, 1999.

  2. Dr Phillip Nitschke with Dr Fiona Stewart, The Peaceful Pill eHandbook (, revised 6 August 2010.

  3. Alt Suicide Holiday,