Public Buildings Should Mandate Cleaner Air

International group of scientists call for indoor air quality standards to be introduced.

Australia’s bushfire season of 2019-20 was unprecedented in its intensity and magnitude. An area the size of the UK (59 million acres) burned. Billions of animals killed or displaced. Thousands of homes destroyed. Hundreds of human lives lost or irrevocably changed.

It was also the first time that Australians really became aware of the importance of good indoor air quality, says Distinguished Professor Lidia Morawska from Queensland University of Technology. “I did lots of interviews during that time; what to do, how to protect people. The advice I gave was to close up the buildings as much as you can, make sure that air doesn't enter from outside, and if you can avoid going outside, do.”

Prof Morawska is a physicist who has been working on air quality for more than twenty years. She carried out research related to the SARS outbreak in 2003, and established much of the fundamental understanding of how particles from respiratory activities (like breathing) behave in indoor environments. “All of that knowledge, those findings made me say ‘well, we clearly need to do something about building ventilation, and protecting people indoors from airborne transmission.’”

With most people in urban and industrialized societies spending 80 – 90% of their time indoors, ensuring that the air they breathe is clean seems like an important thing to do, but she says, in the years to follow, it became harder to convince funding agencies to support their work, “For a very long time, once the SARS-1 epidemic was over, there was very low interest in this. Getting a grant on indoor air quality was pretty much impossible. In 2014, one reviewer even commented that airborne infection transmission was not possible!”

And then, in December 2019, the world changed.

The COVID-19 pandemic, coupled with the Australian bushfires, put air quality and ventilation in the spotlight. “I spoke to the same journalists again,” says Morawska, “but this time my advice was 180° opposite – for COVID, I was saying open up everything, don't recirculate air, be outside as much as possible.”

“I remember very early in the pandemic, seeing these huge signs saying ‘wash hands, save lives’, and I thought, ‘this isn't going to save any lives.’” Within a few days of seeing those posters, Morawska established what's now called ‘the group of 36’, all leading experts on air quality and aerosols. “That was when we had the first battle for recognition of airborne infection transmission.”

In the end, Morawska was instrumental in convincing the World Health Organisation (WHO) and other authoritative bodies to recognize that the coronavirus could be transmitted via air – or more specifically, via the exhalation and inhalation of virus-laden aerosols. And ever since, she’s continued to advocate for the provision of adequate indoor air quality for homes, schools and other spaces.

A call to action

In a new Insights paper, published this week in Science, Prof Morawska teamed up with 42 other scientists to call for the introduction of national indoor air quality standards for public buildings. They’ve proposed maximum levels of carbon dioxide (CO₂), carbon monoxide (CO), and fine particulate matter (PM_2.5), as well as an ideal ventilation rate (measured in liters per second per person).

“Most countries do not have any legislated indoor air quality performance standards for public spaces that address concentration levels of indoor air pollutants,” Prof Morawska explains. This stands in contrast to outdoor air, where national regulations and laws that set minimum air-quality standards have been widely adopted.

For many reasons, mandating indoor air is a much more complex endeavor. Indoor air contains a much more diverse range of pollutants than outdoor air does, though some are common to both. Natural-gas boilers give off nitrogen oxides (NO_x), wood-burning stoves produce PM_2.5, building materials emit formaldehyde, volatile organic compounds are released from paints and carpets, fire retardants are commonly added to furniture, and mold thrives in damp, poorly ventilated buildings. And then there are emissions from a building’s occupants – us – we breathe out carbon dioxide and occasionally, viruses and bacteria. Indoor air is also heavily influenced by the air outside (the reverse is rarely true). This diversity makes it challenging to define what ‘good air’ actually is.

In addition, while cities very often have numerous monitoring stations to measure outdoor pollutants, the same can’t be said for most public buildings. And even in those buildings that have installed air quality meters, “we cannot rely on monitoring in one room to conclude what's happening in room next door,” says Morawska. “There are also no technologies yet that can measure pathogens in real time. Really, we need monitoring in every room of any public buildings, which means it has to be done well, but in a much simpler, much more pragmatic way, because otherwise it won't be possible.”

The three metrics that Morawska and her colleagues have presented in their paper can be considered useful, easily-measurable proxies for all other contaminants, and the proposed ventilation rate provides a way to assess a building’s ventilation quality. The overall goal is to dilute and remove pollutants at a higher rate than they’re produced, to stop them from accumulating in indoor air.

“We propose a CO₂ concentration level of 800ppm [parts-per-million] with the proviso that outdoor concentration is used as a baseline,” says Morawska. “For PM_2.5, we propose using the WHO air quality guidelines as the basis [15 µg/m³], but reducing the averaging time.” They’ve also suggested 15-minute, 1-hour and 8-hour averages for CO levels, with 14 l/s per person as the optimal ventilation rate for an occupied room.

Achieving this may involve expensive retrofits, or a wholesale redesign of public buildings – another developing area of research for Morawska – but she says, the advantages are clear, “While there is a cost in the short term, the social and economic benefits to public health, well-being and productivity will likely far outweigh the investment in cost in achieving clean indoor air.”