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Is outdoor air quality more important than indoor?

The believer.


Outdoor air pollution has been linked to cancer, asthma, cardiovascular disease, diabetes, obesity, and dementia. With approximately 40,000 deaths estimated to be attributable to outdoor air pollution in the UK annually, it’s a serious matter that can’t be ignored.

So what’s causing it? In urban areas, outdoor air pollutants are mainly emitted from on-road and off-road vehicles, but there are also contributions from power generation, incinerators, and industrial process, depending on the locations and prevailing winds. Emissions-wise, approximately 1.5 million homes use wood for fuel across the UK, and burning wood/coal in open fires and stoves makes up 38 percent.

By comparison, 16 percent comes from industrial combustion, 12 percent from road transport, and 13 percent from the use of solvents and industrial processes. In fact, a wood burning stove emits more particles per hour than a diesel truck.

From outside to in

Improving outdoor air quality relies on national and societal change, led principally by the government. We’re starting to see more Clean Air Zones being introduced across the UK; these are designed to cut pollution and encourage people to drive less polluting vehicles (i.e. electric and more modern petrol/diesels).

Our indoor air is supplied from outside: both actively through mechanical and natural ventilation, and passively via gaps or leaks in doors, walls, and windows. Only one of these three sources of outdoor air allow us to control the resultant internal air quality.

Ultimately, without improvements and controls to reduce external sources of emissions, the air we need for inside our buildings will only be further polluted.

The sceptic.


As individuals we spend 90 percent of our time indoors, spread between home, work, socialising, our commute, and other places like the gym etc. Given that the impacts of poor air quality are linked to our exposure (the time spent in an area) it stands to reason that, to reap the most benefit, efforts should be focused towards the areas we spend the majority of our time in.

While the indoor environment is of course linked to the outdoor environment, we still very much have the ability to control and influence it, especially from indoor pollutant sources. The indoor space can also offer a vital refuge from poor outdoor air quality, which to a degree is out of the control of the individual.

Indoor opportunity

Most of us are able to manage our bodily intakes: we watch what we eat and drink. However, our intake of air is pretty much out of our control when we are outdoors, and is down to the government to address. By comparison, a building’s ventilation strategy is something we, as air quality consultants, can actively design to protect people.

There is no safe limit in terms of exposure to air pollution. Of course, standard limits must be achieved, but I believe it’s important to move beyond compliance and deliver further benefits to a building’s users. Good indoor air quality can improve cognitive performance, result in fewer incidents of illness, and lead to better mental and physical wellbeing.

Simply put, the indoor environment provides us with a real opportunity for control to be given ‘back to the people’, so to speak. For example, an organisation can take action to manage the air quality of its working environment.

Given how large a proportion of an individual’s exposure is in this environment, buildings can present significant opportunities to help manage people’s ‘daily intake’ of air pollution as we all go about our lives. Using our buildings to create environments in which everyone can thrive is vital to our collective health and happiness.