What you need to know about air purifiers

Air purifiers are often marketed with claims that they can remove bacteria, haze particles, viruses like Sars-CoV-2, which causes Covid-19, and the chemical formaldehyde, among other pollutants.

- Osmond Chia

But in reality, the devices' effectiveness depends on how they are used indoors and other factors that are tricky for the average consumer to ascertain.

Experts interviewed by The Straits Times clear the air on purifiers.

HOW DOES AN AIR PURIFIER WORK?

An air purifier uses a fan to draw air from a room through one or more filters, before releasing the clean air into the space.

Some purifiers have Hepa, or high-efficiency particulate air, filters that remove particles as small as 0.3 micron, such as dust, fur and some bacteria. Some other devices come with photocatalytic or activated carbon filters, which are effective in removing odours and gaseous contaminants.

Certain air purifiers have germicidal ultraviolet light or ionisers to eliminate pathogens and viruses.

But experts and the National Environment Agency (NEA) have cautioned against using those that release ozone gas, which is a lung irritant.

CAN AIR PURIFIERS REMOVE FORMALDEHYDE?

Air purifiers are designed to extract formaldehyde - commonly known as "new house smell" from the air. But experts are sceptical about their effectiveness outside a laboratory setting.