A customer looks at air purifiers at a shopping center in Beijing. Various kinds of air purifiers have appeared in Beijing after air pollution frequently reached dangerous levels during the winter. [Photo/China Daily]

It is worrisome to live in a city that constantly issues red alerts for heavy smog. But what was even sadder was when I found out about the skyrocketing prices for the filters for my three air purifiers.

At the store of the Swedish company which manufactures the air purifier, each filter costs about 300 yuan ($46) and the largest one is 700 yuan. But the almost dark gray filters, which were white when I first installed them convinced me the cost was worth it. It is hard not to imagine those dark gray filters could be our lungs if we didn't use such air purifiers.

Such psychological factors are what has pushed up the sales for major air purifier manufacturers. Though the air smells a little fresher in a room with such a purifier, the sheer price for such machines is still relatively high. A leading air purifier for a 30 square meter room costs nearly 5,000 yuan.

However, there are alternatives. My friend Zoey shocked me when she posted on her WeChat a photo of a do-it-yourself air purifier. She bought it on Taobao for 120 yuan, and each filter costs just 35 yuan. The purifier is made of an ordinary fan, with a HEPA filter on top of it. Zoey said the machine performs a similar function as her expensive air purifier, as test results show the PM2.5 is at a safe level after it has been running for just 30 minutes. The only weakness is the noise. "If you shut it down, it feels that at least two people have walked out of the room," she joked.

She said the idea came from an online posting by Swedish engineers. Later the model was copied and developed by many Taobao retailers.

It reminded me of a story I heard the last time I was invited to the Swedish embassy in Beijing where a friend said that Swedish government gives out free lamps for people who couldn't afford a trip to Southern Europe in the long dark winter, as a way to fight against depression.

If the low-cost air purifier my friend uses is actually effective, and if this was proven by scientific testing, government or charitable organizations could raise funds for such machines or subsidize their manufacturers in order to make them affordable for everyone.

According to research findings released by Honeywell, 60 percent of Chinese are worried about indoor air quality and the majority want improvements to indoor air in public facilities and the workplace. Nearly 80 percent of respondents consider household air purification an absolute necessity, but many have insufficient knowledge of air-cleaning technologies and products.

Interestingly, even when they have bought an air-cleaning device, more than half of those surveyed doubted whether their devices were doing any good. In addition, 84 percent questioned whether they were functioning as they were supposed to.

According to Wang Li, a senior research fellow at Honeywell Technology Solutions in China who specializes in air-cleaning technologies and solutions, consumers appear to be more familiar with devices that humidify or remove odors than those that actually clean the air. Those core technologies include medium filtration, electrostatic filtration and fresh air systems.

"That might explain why only 16 percent of respondents said their purifiers were functioning as expected and 56 percent said they were uncertain if their purifiers were actually effective. More knowledge about critically important technologies could make a tremendous difference to indoor air quality," said Wang.

It occurs to me that it is crucial that we raise awareness and knowledge of how we fight heavy smog and bad air. In addition, it is essential to make air quality improvement solutions more available and affordable to everyone in society, even if it is just a free mask.