KITCHENER -- Health officials now say that wearing a non-medical mask could help stop the spread of COVID-19, but only when used correctly and paired with physical distancing as well as frequent hand-washing.

Experts say that the N95 respirator masks worn by health care staff on the frontlines are about 95 percent effective.

"They minimize the exposure to particles, that includes both small particle aerosols as well as large droplets," says University of Waterloo Prof. Zahid Butt, of the School of Public Health and Health Systems.

But with a limited supply of medical-grade masks available, health officials are now recommending the public wear cloth masks in certain circumstances.

"Where you cannot maintain physical distancing of 2 metres, such as public transit or grocery or pharmacy stores," explains Butt.

However, the University of Waterloo public health professor stresses it does not make healthy people immune from the virus.

"They should still be safe. They should still do frequent hand washing. They should still maintain that physical distancing," he says.

Experts say cloth masks only prevent some germs of those wearing it from spreading to others, and not vice versa.

Adding they would be best worn by those who are a-symptomatic or pre-symptomatic and remember to keep your hands off your face.

"You shouldn’t touch the mask, and if you have touched the mask, you should always wash your hands," says Butt.

He says that cloth masks can be homemade and can be washed.

"You can wash them in a washing machine," explains Butt.

Butt warns though that he hasn’t heard of any studies claiming the material would be completely virus free after being washed.