Sign in with Microsoft

Australia is in the grip of a horrific bushfire season. Our hearts go to those who are living through hell. Add that to the drought and the lucky country is not so lucky. Thanks, Mr Dyson for making us all aware of a thing called Air Quality.

Because of the fires, dust clouds from the red centre, temperature inversion and spring pollen, air quality is at its all-time worst – Sydney beating Beijing – a record we don’t want or deserve. Few have done as much as Mr Dyson to let us know there is relief at hand.

Today (15 November) areas of Sydney are at PM227 which is hazardous to health. It is a long way to less than PM2.5. Fortunately Mr Dyson and others have products that can help.

Air Quality Index

The sufferers are those with asthma, hay fever, and respiratory tract diseases. I am a chronic hay fever sufferer living on antihistamines and using boxes of tissues, so I understand the need for clean air.

We have reviewed several air purifiers, and I am now a firm believer that they do work – just look at the Dyson generated graph at the end of the article.

We have reviewed many purifiers, but I wanted to single out a few that really make a difference – and by that I mean really extract smoke, dust, pollen and more from the air.

It is all about CADR (clean air delivery rate) – even more so than filter efficiency, although that is important too.

CADR is cubic meterage per hour (m3/hour).

How do you know a room cubic meterage? Well, it is a room’s length x depth x ceiling height. We will use the example of lounge 5 x 5 x 2.4m or 60m3. And there are 1000 litres of air per m3, so that is 60,000 litres to clean.


Of course, you need to consider whether that room can be enclosed (like a bedroom with a door and windows) so it is a closed ecosystem. Or if it is more open (like an open plan lounge/dining/kitchen with perhaps a hallway and stairwell to other levels), then it is an open ecosystem.

Now the great thing – Catch 22 – is that once the air is clean in a closed ecosystem, then the job is done until more dirty air is let in (opening a window or door). The rule is that you always over-order CADR capacity for open space and you can get away less with for closed spaces.

Mr Dyson

Mr Dyson and his impeccable British accent and smiling visage have done more to make us aware of the need for pure air than any other ‘brand’. He has invested millions in developing test labs, building prototypes and keeping half the British engineers employed – not to mention advertising agencies as well.

Mr Dyson

While as a journalist, I am paid to be sceptical, I now appreciate the engineering and science behind Dyson products and the pursuit of perfection.

While Dyson’s products are at the upper end of the budget, they are quality products and the Dyson Link app provides lots of great information on external and internal air quality.

Dyson app

Dyson has a range of Pure Hot and Cool devices that are at the top end of air purification, but they are best in smaller, enclosed spaces. All Dysons use a separate HEPA filter and activated charcoal filter that must be replaced after about 4,000 hours and provide the highest filtration rate of all – particles, noxious gasses, etc. They cost about $110 per pair.

Dyson filters

Dyson Pure Cool series  ($649-799)

These have a CADR of around 35-40 m3/hr. That means it cleans the air in the lounge example one time per 2 hours. These are perfect for enclosed spaces. For example, today in a 100m2 area, it took about four hours to bring the room down to the ‘green’, but after that initial clean it can keep it there.

Pro – low electricity cost, great for smaller enclosed spaces
Con – A fan does not heat so it may be more useful to buy a Pure Hot and Cool unit