• HEPA filter is a good start but there is more to it
  • The higher the CADR the better
  • Hear the noise
  • Energy consumption shouldn’t be a deal-breaker
  • Some can do more e.g. Remove odours, can be a fan, remote managed

The Singapore Haze is back and it is time to roll out your air purifier, but is that old air purifier of yours adequate to fight the current haze? Which model should you get? And what is PSI, PM2.5, Micrograms and Microns? 

Let’s start by understanding the elusive Haze and how it’s measured. 

The current haze situation is caused by the forest fires in Sumatra, Indonesia and unfortunately, due to the wind direction, dust, smoke and other pollutants from the fire have reached the shores of Singapore. These harmful particles can cause serious health issues. To keep Singaporeans informed of the situation, The National Environmental Agency provides regular updates of the haze situation. PSI stands for ‘Pollutant Standards Index’. It is an index of the daily levels of air quality. The PSI measures pollutants by its size – e.g PM10 (Particle size of 10 microns and below), PM2.5 (Size of particle below 2.5 Microns which can easily penetrate into human body) – a few common types of pollutants – Sulphur dioxide (SO 2), Nitrogen dioxide (NO 2), Ozone (O 3), and Carbon monoxide (CO) – and its concentration.  For example, at the time of writing, the PSI is at an Unhealthy level due to the high concentration of all or some of the measured pollutants. E.g. PM2.5 @ 73 – 90 µg/m3 (microgram). 

1. Filters

Most Air purifiers come with HEPA (high-efficiency particulate air) filters. Products advertised using words like “HEPA”, “HEPA-like”, “HEPA Type”, “99% HEPA”, may not be using a True HEPA filter. A True HEPA standard filters can filter particles as small as 0.3 microns (A human hair is about 100 microns, so it’s about 333x smaller) which should be sufficient to filter out most harmful contaminants. That said, some viruses, oil smokes, lead and pesticides, to name a few,  can still be smaller than 0.3 microns. So getting a filter that can capture even smaller particles will be great. Some air purifiers like the Dyson Purecool claim to be able to capture pollutants as small as 0.1 microns using their proprietary Glass HEPA filters and it can also remove smoke and odours. Very few air purifiers can provide similar functions, and they will still need a separate carbon filter for odour removal and a washable pre-filter for larger dust particles. 

Credit: Dyson

2. Coverage

Clean Air Delivery Rate (CADR) is the word you will be looking for if you want to find out how much air and how fast an air purifier can clean. Most of the reputable air purifiers have CADR at 300-400 Cubic Feet Per Minute and it easily cleans the air of an enclosed regular size HDB room within a few minutes (at maximum speed).  So if you intend to clean the air of a larger space, do go for one that has higher CADR. However, there is another school of thought. Dyson feels that the CADR rating doesn’t measure how well the particles are captured and how well a purifier can keep the pollutants from the cleaned air. They use their own testing methods and claim to be able to capture 99.95% of contaminants.

3. Noise

A better filter may be noisier because the motor will usually need to work harder to pull the air through the strong filter. Some newer purifiers do manage to bring the noise down, so do give it a listen first before deciding.

4. Power Consumption

Most air purifiers consume about 50-60watts. That’s much lower than an air conditioner and slightly less than a ceiling fan. So even with a full day’s usage, it shouldn’t increase your electricity bill by much. 

5. Bells & Whistles

Space is a commodity, especially with the rising property price. So for those who are willing to fork out a little more, you can get an air purifier that can double up as a fan like the Dyson Pure Cool. If you are a clean air freak, whatever that means, the advanced version will automatically detect all the particles and gases. It gives you a detailed real-time PSI report from its display. If you have kids and old folks at home, it will be useful to use the app to monitor the air quality and managed the purifier when you are outside. 

This article is written in collaboration with Dyson.