The exhaled carbon monoxide (CO) test detects exposure to CO in the last 12-18 hours. This can be used to assess smoking status AFTER a quit attempt and used prior to a quit attempt as a motivational tool. Higher levels (parts per million) equate with greater inhalation of tobacco smoke assuming the cause is tobacco smoking. It must be noted that the exhaled CO test indicates recent exposure to CO and will not indicate smokeless tobacco use and is not a measure of dependency. In pregnancy, a CO of 3 ppm has been proposed as an appropriate cut-off for referral to stop smoking services.

The cotinine test is more specific for nicotine exposure and may be useful in the context of infrequent waterpipe use or smokeless tobacco use and can also be collected via a urine sample in the case of children who may be exposed to environmental tobacco smoke. It is not useful for people who use NRT or e-cigarettes/vapes and is a laboratory-based test.

Pack years provides a measure of exposure; this calculator also allows the evaluation of cigars, roll-up cigarettes, pipes, tobacco by weight and water pipe use and converts them to pack-year equivalents).  To calculate pack-years, you must divide the number of cigarettes smoked per day by 20 (a standard pack size) to get the number of packs per day, and then multiply that result by the total number of years the person has smoked. For example, smoking 10 cigarettes daily for 20 years results in 10 pack-years (10/20 = 0.5 packs/day; 0.5 packs/day * 20 years = 10 pack-years).  There are a number of free online Pack Year calculators