Carbon Monoxide

Carbon monoxide is a very deadly gas, which has:


In short it can not be sensed by the human body .......... but can KILL!

The early symptoms of CO poisoning can be as others associated with colds or other ailments. A headache is one of the first signs - this quickly increases to feeling tired, nauseous, dizzy and faint. So curl up in front of a fire emitting CO and you may feel tired, fall asleep and not wake up. If such symptoms occur then we suggest the following:

  • Seek medical advice - Doctors are becoming more aware of CO symptoms.

  • Have your boiler/fire checked by a reputable heating engineer (ask to see their CORGI registration card). It is also preferable that they have an instrument that measures CO (it is however not a statutory requirement they carry one).

  • For increased security fit a wall mounted alarm with a British Standard 'kite' mark.

Toxic Symptoms

Note: PPM = parts per million (10,000 PPM = 1% by volume)

In the USA the Environmental Protection Agency (EPA) have set a maximum level of CO in the flue at 400 PPM.

In the home a concentration of no more than 9 PPM is recommended. While at work during an 8 hour period the level should not rise above a maximum level of 35 PPM i.e. if you are exposed to 35 PPM for 8 hours you should be in fresh air (zero PPM CO) for the remainder of the 24 hours.

9 PPM The maximum allowable concentration for short term exposure in a living area according to ASHRAE.
35 PPM The maximum allowable concentration for continuous exposure in any eight hour period, according to federal law.
200 PPM * Maximum concentration allowable at any time according to OSHA. Slight headaches, fatigue, dizziness, nausea after 2-3 hours.
400 PPM Frontal headaches within 1-2 hours, life threatening after 3 hours. Maximum allowable limit in flue gas according to EPA and AGA.
1600 PPM Headache, dizziness and nausea within 20 minutes. Death within 1 hour.
3200 PPM Headache, dizziness and nausea within 5-10 minutes. Death within 30 minutes.
6400 PPM Headache, dizziness and nausea within 1-2 minutes. Death within 10-15 minutes.
12,800 PPM Death within 1-3 minutes.

* exposure to this concentration and higher, the effects can vary depending on size, age, sex and health.

Where does CO come from?

CO is produced by incomplete combustion in a heater or boiler. As burning fuel is starved of air it generates higher levels of CO, this is due to there being insufficient oxygen to produce carbon dioxide (CO2). CO2 is produced when carbon in fuel is fully burnt and all the heat released. With a shortage of oxygen the carbon does not fully burn and produces carbon monoxide (CO).

In a domestic boiler CO can be produced by the following problems:

  • Blocked flue not allowing the products to escape.
  • Inadequate air supply causing a shortage of oxygen.
  • Flue products entering the air supply and causing a shortage of oxygen.
  • Worn burner parts causing incomplete combustion of fuel.
  • Any of the above causes, linked to conditions where CO can enter a room, is a recipe for disaster or ultimately... DEATH!

Can you be sure there is no CO?

As the human body cannot detect CO there is only one option available and that is use an instrument that can measure it. For the boiler installer there is a wide range of CO detectors on the market to fit all applications. To select the most suitable use the "Hello I'd like to buy a CO tester" to aid your decision.

How does CO kill?

CO is absorbed by red blood cells through the lungs. Taking the place of vitaloxygen, the CO is transported by the blood to organs such as the brain. Oxygen is one fuel that enables organs to work correctly; if not available in the blood then these organs can malfunction. As the build-up of CO becomes more severe, cells in the body are killed with the ultimate conclusion.... DEATH!