Smoke Terminators Society chairwoman Betty Kwan Ka-mei said the invention could help smokers quit the habit by making them more alert to bad breath caused by nicotine.

Dr Kwan, a family physician in private practice, said the handset might help detect health problems, since bad breath was a common symptom of illness.

'Bad breath can be caused by many things, ranging from simply poor oral hygiene to gastrointestinal problems or respiratory and chest infections to serious ailments, including liver and renal diseases,' she said.

'It is not easy at all to persuade young people to quit smoking, as they believe it is cool to light a cigarette and take a puff in public.

'But the new device could effectively remind them of the embarrassment caused by cigarette [odours].

'My major concern is whether it would create additional radiation that may pose a health risk to the users.'

According to Siemens, the phone analyses air for anything from bad breath and alcohol fumes to atmospheric gas levels. But the manufacturer did not say what the phone would do if it found the user too smelly. Will it ring out an alarm or send out a high-pitched scream that says 'bad breath' to anyone nearby?

Tommy Chan Ka-chi, who is in his early 30s, described the new product as 'cool'. The audit clerk said he sometimes suffered from bad breath, especially after eating his favourite foods, such as durian.

But Mr Mui, a lawyer, said: 'Personally I won't buy this new phone because I am so confident about myself. But I have no objection to this new product. That may also be the attitude of other professionals who need to meet people every day, like me.'