CO Sleuth FAQs

Q. What does a CO breath test show?
A. It shows the amount of carbon monoxide (ppm CO) in breath, which is an indirect, non-evasive measure of blood carboxyhemoglobin (%COHb).

Q. What does ppm mean?
A. Parts Per Million. In this case one part CO in one million parts air (breath). 1ppm is like 1 inch in 15.5 miles!

Q. How does smoking elevate COHb?
A. In a 'typical' puff of a cigarette smoke there is about 5% by volume CO. This will compete with oxygen very successfully to form COHb (combination of CO and blood). This will eventually be excreted via the lungs; the same way it went in!

Q. What else does breath CO show?
A. It acts as an indicator as to the possible level of some 4000 toxic substances in cigarette smoke, some 60 of which cause cancer.

Q. How quickly does the CO disappear from the body after smoking stops?
A. It takes about 5 to 6 hours to reduce the original level by a half. Usually after a maximum period of 48 hours the ex-smoker would show the level of a non-smoker living in the same environment.

Q. How long after a cigarette should the test be conducted?
A. More than 10 minutes.

Q. What levels of breath CO do you expect to see?
A. Clinical research has shown that the best guidelines are (ppm)

0 -10 non-smoker
11 - 20 light smoker
21 - 100 heavy smoker

Q. If a smoker cuts down, will this reduce breath CO by an equivalent amount?
A. Probably not. A smoker may smoke fewer cigarettes, but will require the same amount of nicotine. Thus, they may smoke smaller number more aggressively and hence inhale more smoke than expected (and thus more CO).

Q. Is it necessary to hold the breath before taking a test?
A. Not absolutely necessary. Clinical research has shown that an optimum period of 20 seconds breath hold is required to get the best correlation with COHb. A 15-second breath hold gives almost the same correlation. Less than this will depress the breath reading. However, as long as the person is encouraged to exhale completely, this 'end-tidal' breath sample will give a good indication.

Q. Do cigars and pipes give low readings?
A. No. On the contrary. An inhaled puff of pipe or cigar smoke is much more concentrated and will give surprisingly high COHb.

Q. Why do non-smokers sometimes give higher than expected readings?
A. This could be for several reasons:

They have been exposed to high ambient levels of CO. For example, at home or in the car. It could be useful to check other family members in order to eliminate possible chronic CO poisoning.

Certain occupations may expose workers to high CO levels. A degreasing agent called trichloroethylene is metabolized by the liver to produce COHb.

Some CO monitors may have a cross interference from other breath constituents. The most likely ones are alcohol and hydrogen. The latter maybe present due to a gut condition called lactose intolerance an allergy to dairy products that produce hydrogen gas in the intestines. Some of this gas maybe excreted via the lungs. This condition exists in about 5 to 15% of Northern Europeans.

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