If the mask fits...(2)

N95 mask

These masks are recommended by doctors to be effective against pollution, Saint Cyr explained. The name N95 comes from US government certification that the fabric filters out 95 percent of the PM2.5 matter. It's used in construction sites for dust and small particles, he said.

However, Saint Cyr noted it's not enough for the fabric to block out PM2.5. Fit is far more important.

Many companies make the N95 mask, but 3M makes the best, according to Saint Cyr.

"The 3M series has the most documented protection. I think they have the best reputation," he said.

Protection: The fabric is certified to block out PM2.5 matter, but you may need to try on each to see how the mask fits with your face. The 3M mask comes highly recommended.

Comfort: The mask gets wet after a while from your breath.

Breathing difficulty: It's a little hard to breathe when having this mask on, and people with heart diseases or breathing difficulty should take precaution.

Obstruction of vision: You may need to take your glasses off, otherwise things will get steamy.

Cost: 25 yuan

Totobobo mask

Saint Cyr rates the Totobobo brand as the second-best after the 3M series.

"I tried it around town for a bit, and the overall comfort is good. I was pleasantly surprised with the seal and that my glasses didn't fog up, although I did get those mask lines on my face. It's relatively easy to keep on, with straps either behind the ear or behind the head (which always provides a closer fit)," he wrote on his blog.

Protection: Even on a headline-making day with the AQI over 500, the mask can bring your air to WHO-safe levels.

Comfort: They fit well and there are kid sizes.

Breathing difficulty: Along with the same lines of the 3M mask, people with heart diseases or breathing difficulty should take precaution.

Obstruction of vision: These masks don't fog up your glasses.

Cost: 160 yuan

Pollens and allergies

Since spring is nearly upon us, Saint Cyr also has some advice on wearing masks to block out pollen for people with allergies. He says as long as you have something on to cover your mouth and nose, you can be protected.

"Pollen is much bigger than PM2.5, so if you have anything on, any regular mask, it will help with allergies," he said. "But of course if you have serious allergies, you still need to take pills."