How to choose an air purifier


November truly is a mixed bag of a month. On the one hand, we’re now free to frolic with friends and family and get our retail fix in stores. On the other hand, the air is made almost entirely out of pollen, we’re hitting bushfire and thunderstorm asthma season, and there’s that pesky pandemic still haunting us at every turn. With all those things comes the importance of clean airflow, and thus air purifiers. So, do you need one, what are the important things to look for, and what should you do with it?

Firstly, you need an air purifier if you have allergies or asthma, live with someone who is unwell with an airborne virus you don’t want to catch, you cook a lot, and/or live in an area near a busy road or a lot of smoke.

Purifiers need to be well-sealed, good at pushing air around and powerful enough for your space.

Purifiers need to be well-sealed, good at pushing air around and powerful enough for your space.

The Victorian government recently purchased more than 50,000 purifiers to put in school classrooms to reduce the COVID burden and transmission in those settings. Shop, restaurant and beauty salon owners should also consider getting a good purifier to reduce the risk for staff and customers.

Air purifiers are designed to remove ridiculously tiny particulate matter from the air, with PM2.5 (2.5 microns) being the most dangerous. The WHO recently revised its Global Air Quality Guides and suggest limiting exposure to just 5 micrograms per cubic metre, down from their previous suggestion of 10. A recent study suggested that changing the safe limit in America from 12 down to 10 would save around 200,000 lives a year, so air pollution isn’t a trivial thing.

The problem with capturing such tiny particles is that if they’re small enough to pass through our lungs and into our blood, the purifier is going to need to be extremely well sealed to stop it from just becoming a PM2.5 dispenser. It also needs to be able to efficiently move the clean air around the room.

The absolute bare minimum thing you need in an air purifier is a HEPA filter. Beyond that, a powerful fan is extremely important (for the circulation) and I’d recommend a carbon filter for gasses, smells and VOCs. When choosing which size model you need, it’s better to always round up. Each model should show you the size of the room it’s designed for in square metres, and the clean air delivery rate (CADR) in cubic metres; for CADR, bigger numbers are better. As well as having a strong fan speed, it’s nice if the purifier also has a variety of speeds, including an extra-quiet night time mode, if you plan on using it all the time.

I’ve been using four different purifiers for the last couple of years, and three of them have really impressed me.

I would not recommend a Philips purifier, as every one I’ve used has had a filter sensor error and died an irritating death shockingly quickly.

The Dyson Hot + Cool Link Formaldehyde does an extremely good job of purifying a space of up to 81 square metres equally (rather than just the area around the purifier), while also heating or fanning. Being able to check the particulate counts and gas levels in the app or on the screen is very helpful, and it’s sealed and tested well beyond the industry standard.