believed to be less harmful than cigarette smoke, but is it true.

The facts: As cigarette bans have proliferated in recent years, hookah lounges have become a popular alternative, in part because the flavoured smoke is believed to be less harmful than cigarette smoke. But research suggests otherwise.

It is true that in hookahs, also known as water pipes, the smoke is often flavoured and filtered through water. The problem is that people who use hookahs typically inhale far more smoke than cigarette smokers, exposing them to potentially higher levels of nicotine, carbon monoxide and other chemicals.

Most studies show that small water pipes produce the highest levels of carbon monoxide, followed by cigarettes and then large water pipes.

One extensive report on hookahs was published in 2005 by the World Health Organisation. It found that in a single smoking session, cigarette smokers typically took 8 to 12 puffs and inhaled 0.5 to 0.6 litres of smoke over five to seven minutes.

In contrast, hookah smokers may take 50 to 200 puffs of up to a litre of smoke each during a single session. "The water pipe smoker may therefore inhale as much smoke during one session as a cigarette smoker would inhale consuming 100 or more cigarettes," the report said.