ResearchBreath easy? Not inside. Dyson report shows indoor air quality dirtier than outdoor air.

The Dyson Global Connected Air Quality Data project analyses more than half a trillion data points to paint a picture of the air quality in real homes around the world, understand user behaviours and compare indoor and outdoor air quality.
Content Team5 months ago8 min

A new report from Dyson’s first Global Connected Air Quality Data project has unveiled startlingly low indoor air quality levels around the world – even from countries such as Canada and Denmark. From 2022 to 2023, Dyson collected data from over 2.5 million Dyson Purifiers in 39 countries in hopes of landscaping air quality ‘to a granularity never seen before.’ While the research demonstrated numbers from an impressive international fleet, the data itself presents a stark reality. 

It should be noted that data is based on homes with Dyson Purifiers and is therefore not nationally representative – but the report still stands to point out that pulling data from these tens of billions of data points helps to ‘paint a picture’ of indoor air quality around the globe on a scale beyond anything that has ever been done before.

“Our connected air quality data allows us insight into the real problem of indoor air pollution in homes across the world. This gives us a direct understanding of the challenges Dyson Purifiers face in real environments and the knowledge to engineer ever-better machines to tackle those challenges,” Matt Jennings, Engineering Director for Environmental Care.

Indoor air quality worse than outdoor air in almost 100% of homes

The study focused on two different types of pollutants: PM2.5 and Volatile Organic Compounds (VOCs). In the case of home indoor air quality, all countries except four exceeded PM2.5 levels for 6 months or more. The UK and Germany saw indoor levels surpass mPM2.5 monthly averages for 11 months in 2022. An even higher number saw PM2.5 levels exceed every month throughout the year: China, Australia, France, Austria, Canada, and Spain.

In cities, indoor air quality further declined. Milan homes, for example, recorded PM2.5 levels almost 3 times higher than outdoor levels. After Milan, other major cities with higher than average PM2.2 levels included: Shenzhen (97% higher indoors), Amsterdam (76%), Seoul (53%), Madrid (50%), Melbourne (40%), Vienna (37%), Singapore (36%), New York (35%) and Tokyo (24%). 21 cities of 35 studied experienced annual average PM2.5 levels higher indoors than outdoors.

Winter showcases highest pollution levels

While most of us have read that we spend 90% of our time indoors, the Dyson report unearths what we’re actually breathing in during this time. The purifier data demonstrated that, globally, the air was showed most particle pollution during the winter months. Shut windows, indoor heating and even lighting candles can contribute to lower ventilation levels and higher pollution. Alternatively, July was the month with the lowest recorded monthly pollution level.

Evening hours show peak levels of pollution

Throughout the day, evening hours after work consistently showed the highest levels of air pollution for the majority of countries studied. In the UK, PM2.5 levels peak between 7pm and 10pm, a timeframe that aligns with elevated evening pollution observed in various countries, including Ireland. The measure of exposure, crucial in air quality research, emphasises that prolonged exposure to ‘fair’ or ‘poor’ air quality can be as impactful as short-term pollution spikes. Dyson purifier data indicates that this prolonged, more polluted evening period may contribute to increased PM2.5 exposure in homes, particularly during the hours when people typically spend time indoors.

For more information, see the full Dyson Global Connected Air Quality Data project here.


The Dyson Global Connected Air Quality Data project analyses more than half a trillion data points to paint a picture of the air quality in real homes around the world, understand user behaviours and compare indoor and outdoor air quality. The total global sample size is 3.4m. In the UK, the national sample size is 149k, and at city level, 39k in London. The indoor air quality studied is based on the location of Dyson Purifiers in homes and as such is not nationally representative.

Indoor air quality data is taken from Dyson Purifiers that are connected to the MyDyson app and in monitoring-only mode – that is, not actively purifying the space. Whilst this reduces the sample size for the calculation, Dyson data scientists can be confident that it is an accurate representation of air quality in real homes, without the impact of Dyson Purifiers actively cleaning the air. 

Content Team

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