Friday (May 31) is World No Tobacco Day, so it is timely to revisit the problem of secondhand smoke.

To avoid the perimeter of office buildings where smoking is disallowed, smokers gather at informal “smoking corners” that have emerged over time.

Take, for example, the public square cradled by Exits A, B and C of Raffles Place MRT Station.

Thick cigarette smoke assaults you when you leave the station to get to nearby buildings.

Then there is the corner at McCallum Street between SGX Centre 2 and OUE Downtown Gallery.

While waiting to cross the road, many pedestrians are forced to inhale cigarette smoke.

Dozens of smokers also have their smoke breaks, especially during lunchtime, along Asia Square near Shenton Lane.

The smoke-free zone in the Orchard Road shopping precinct should also apply to the Central Business District (CBD).

There is a heavy concentration of smokers in various parts of the CBD, where many Singaporeans spend most of their waking hours.

To safeguard the health of the thousands of non-smokers exposed to toxic secondhand smoke, we should make the CBD a smoke-free zone, with designated smoking areas.

With a smoking ban there, smokers will gather at the designated spots and non-smokers will know how to avoid them.

The designated smoking areas could be strategically positioned in areas that minimise harm to non-smokers.