Beijing has become world famous for its smog. In January, there were only five days that were not heavily polluted. On Lantern Festival on February 24, the air turned foul again and the weather observatory issued a yellow fog warning. Until 9 pm, 25 out of the 35 monitoring stations in the greater Beijing area had PM2.5 pollution (particles smaller than 2.5 micrometers) values greater than 300 micrograms per cubic meter.
The danger of PM2.5 pollution is widely acknowledged. A study conducted by Peking University and environmental NGO Greenpeace published in December 2012 says air pollution led to 2,349 deaths in Beijing in 2010, and the authors estimate the number of deaths in 2012 to be 2,589.
Masks can shield against Beijing's smoggy air. However, not all masks sold on taobao.com or in corner stores can effectively fight the pollution. Metro Beijing talked to experts and Beijingers who have used masks, from the cheap cotton ones to the high-end ones in order to help you make sense of the spectrum of offerings on the market.
The common, cartoon-adorned masks sold online or on the street, usually made with cotton and a layer of fuzz, can't really defend against the pollution. They're more fashion accessory than anything.
Wang Xiaojiao, a master's student at Beijing Forestry University, bought one with a cartoon bear design from a shop on Wudaoying hutong in Dongcheng district.
"I bought it to block out the cold air more than the pollution. It definitely can't compare with the other masks in terms of protecting you against PM2.5," she said.
Protection: The mask doesn't provide sufficient protection against the pollution; it's not specially designed to do so. But in terms of keeping your nose warm, you can bet on it.
Comfort: Since it's cotton, it's quite comfortable.
Breathing difficulty: The mask doesn't block breathing since it doesn't have filters. Air comes through to your nose quite easily.
Obstruction of vision: When you wear glasses, the steam from your breath can go up and obscure your vision.
Cost: About 5 yuan ($0.80)
Many, especially medical doctors, have access to surgical masks. They are usually made from gauze or paper and used during surgeries in hospitals. But while these masks are great in keeping out dust and larger particles, they can't defend well against PM2.5.
Dr Richard Saint Cyr, a family medicine physician with the Beijing United Family Hospital, tried on many masks during the smoggy days of January, and said he doesn't believe the surgical masks are effective.
"If you are going to wear a mask, you might want to wear a proper mask. Wearing one of these doesn't prevent pollution from getting in very well," he said. "These masks don't really fit your face and there's still tons of air coming in from outside. It helps with blocking out viruses, but if you are blocking out PM2.5, it still needs to be a better fit."
Protection: Good protection against germs, but its efficacy against pollution is debatable due to the air that can leak in due to its one-size-fits all fit.
Comfort: Not comfortable. It's hot and stuffy and tugs on the ears.
Breathing difficulty: Blocks breathing a lot and you can't do any exercise while wearing it.
Obstruction of vision: None.
Cost: 2 yuan
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
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."