What is Carbon Monoxide(CO)?

What is CO?

CO is a poisonous gas that you cannot smell or see. It is formed by combustion and is produced in car exhaust fumes, faulty gas boilers and tobacco smoke

What does CO do to the body?

Heart - To compensate for the shortage of oxygen, the heart has to work harder (beat faster) to get enough oxygen to all parts of the body. The heart itself receives less oxygen, increasing the risk of heart damage.

Circulation - COHb causes the blood to thicken and arteries become coated with a thick, fatty substance. This causes circulation problems and high blood pressure, with increased risk of a heart attack and stroke. Hands and feet can become colder as less blood circulates to the extremities.

Breathing - The reduced supply of oxygen means you can easily become out of breath when exercising, because there is little oxygen available for the increased demand. A lack of oxygen can also cause tiredness and a lack of concentration.

Pregnancy - Oxygen is required by a foetus for healthy growth, but the supply of vital oxygen is reduced when the mother smokes. This increases the risk of low birth weight, birth defects and even Sudden Infant Death Syndrome. A recent clinical study established a direct link between an expectant mother’s breath CO level and the amount of CO in their unborn baby’s blood (1).

1. Gomez, I Berlin, P. Marquis and M. Delcroix. Increased air carbon monoxide concentration in mothers and their spouses above 5ppm is associated with decreased foetal growth. Preventative Medicine (2005) pp 10 – 15.elow.

Why Monitor Breath CO?

CO testing is a quick, non-invasive and cost-effective means of validating your smoking status by looking at the Carbon Monoxide you are breathing out in each breath. Smoking is the single greatest avoidable risk factor for cancer. 

In the UK, it is the cause of over a quarter (29%) of all deaths from cancer and has killed an estimated six million people over the last 50 years (2). Smoking can be attributed to 90% of all deaths from lung cancer, chronic bronchitis and emphysema, showing that if everyone quit the habit, these types of death could be almost completely eradicated (3). Carbon monoxide monitors offer tobacco treatment specialists an independent clinical tool which provides valuable evidence in identifying, educating, assessing and treating tobacco-dependent patient (4). Monitoring your CO levels helps to work out your level of nicotine dependence: the more you smoke, the higher your reading will be, indicating a higher dependence on nicotine. 

You can use the iCO to see your level of CO dropping the less you smoke and therefore your nicotine dependence reducing with it while reducing the amount you smoke. You can also use the iCO to determine a smoker and non-smoker if you have suspicions that someone is smoking, however this is not it’s intended use.


1.  Gomez, C., Berlin, I., Marquis, P. and Delcroix, M. (2005) ‘Expired air carbon monoxide concentration in mothers and their spouses above 5 ppm is associated with decreased foetal growth’, Preventive Medicine, 40(1), pp. 10–15.

2. Lifestyles and Cancer; Tobacco and Cancer risk, available at http://www.cancerresearchuk.org/health-professional/cancer-statistics/risk/tobacco

3. N Willis, E Croghan and M. Chambers. NHS Stop Smoking Services: Service and monitoring guidance 2009/10. pp 17

4.R Bittoun 2010. Carbon Monoxide Meter: The Essential Clinical Tool – the ‘Stethoscope’ – of Smoking Cessation. Australian academic press; pp 69 – 70