Air purifiers are not always effective, and some may be harmful
Air purifiers are not always as effective as advertised, and those that emit ozone may even be harmful, writes Elizabeth Choi
With Hong Kong recording its smoggiest day of the year two Sundays ago, perhaps you were persuaded to not only stay home but also invest in an indoor air purifier.
As the air quality index climbs, so do sales of air purifiers in China. According to Euromonitor International, air purifier volume sales in China rose 87 per cent from 2012 to 2013.
Nowhere in the world is the number of air pollution-related deaths climbing as quickly as it is in Asia, especially Southeast Asia. A 2012 study by the World Health Organisation found that, globally, seven million deaths were attributable to the combined effects of household and ambient air pollution.
Most people live without one, and without any problem
Southeast Asian and Western Pacific regions - of which China is part - bear the brunt of those numbers, with 2.8 and 2.3 million deaths respectively.
In Hong Kong, the Hedley Environmental Index, a real-time health information system developed by the University of Hong Kong's school of public health, shows a city map that is often dotted with red during the day, indicating the WHO level of permissible short-term exposure to fine particulates and other pollutants is more regularly "very bad" than it is green ("acceptable"), or even yellow ("not good").
So can a household air purifier protect your health indoors? It's easy to get your hands on one in Hong Kong - at a wide range of prices.
A new, moderately sized model that can purify up to 48 square metres (or about 515 sq ft) can cost more than HK$4,000, while a used machine can cost as little as HK$290 on classified sites such as AsiaXpat.