Perth researchers have discovered that smoking in open regions puts non-smokers at risk of having respiratory troubles.

Curtin University Professor of Health Policy Mike Daube stated that even in alfresco areas, well-ventilated regions, second-hand smoke showed a risk of health.

The investigations showed that when there was no one smoking, tobacco smoke particle concentrations were about four micrograms per cubic metre of air, however, augmented to 14.25 when at least one person started smoking.

"The amount of second-hand smoke detected increased with the number of people smoking," Daube said.

Curtin researcher Julia Stafford said, "This research supports smoking bans in areas where people may spend extended periods of time, such as outdoor eating and drinking venues." (With Inputs from Agencies)