Author: Philipp Seidel, Project Leader Marketing & Communications

When we think of “air quality”, we tend to think of air pollution in the regions surrounding our homes. We rely on measures such as the Air Quality Index to let us know when airborne pollutants in our towns or cities reach levels that may cause or exacerbate health issues.¹ When summer humidity brings an increased risk for asthma sufferers or when dangerous smog accumulates in cities, the message is simple: to protect your health, stay indoors.²

However, some of the most polluted air we breathe is found indoors. From dust to formaldehyde to radon, unseen elements and particulate matter inside our homes and offices can cause both short- and long-term health issues.³ Given that Americans spend about 90% of their time indoors, measuring and controlling indoor air quality should be a top priority.⁴

With a growing body of research pointing to a link between COVID-19 cases and low humidity and/or high levels of pollution, being able to control and monitor these variables is more important than ever.^5,6 In this article, we explore the causes of indoor air pollution, the steps we can take to improve indoor air quality, and, importantly, the future possibilities for improving indoor air quality in every home.

Fortunately, several practical steps can be taken to improve air quality and safety within the home.

Prevention is better than a cure: the best way to reduce the presence of harmful pollutants in the home is to eliminate their sources. Restricting the use of certain materials in the home and opting for hypoallergenic (or “green”) cleaning products are effective ways of improving indoor air quality. Some sources can be enclosed (such as those containing asbestos); while fuel-burning appliances can be adjusted to decrease the amount of emissions.⁹ However, the removal of sources of pollution is not always practical when so many common household items and materials are known sources of pollutants.

Perhaps the easiest method of air quality control, increasing ventilation can have drastic effects. Cracking open a window, opening a door, or running a window air conditioner are all effective ways of increasing the outdoor air ventilation rate inside your home and preventing the accumulation of harmful pollutants. Kitchen or bathroom extractor fans that exhaust outdoors are also effective at removing pollution directly from those areas and bringing outdoor air into the house.

Air cleaners and filters are effective at removing particulate matter from the air in your home. Although they’re generally not designed to remove gaseous pollutants, reduction of particulates is important for people with asthma and can improve pulmonary function.¹⁰ When choosing an air filter, bear in mind that the performance of different air filters is highly variable – it’s important to choose one that has both a high collector efficiency and a high air-circulation rate, and to change the filters regularly.

Throughout the world, we’re experiencing an increase in the use of networkable sensors and controllers (such as intelligent thermostats, automated lighting, and keyless locking systems) to automate our homes. This increase in home automation, dubbed the “smart home revolution”, offers an opportunity to take control of our indoor air quality.

Developments in environmental sensing technology mean that we can now measure levels of indoor air pollutants such as CO₂, particulate matter, and VOCs with more precise, efficient, and compact sensors than ever before.¹¹ Future smart home systems could use sensors like these to continuously monitor indoor air quality and activate mechanical ventilation systems before pollutants reach dangerous levels.

As well as measuring concentrations of pollutants, such systems are also capable of monitoring humidity levels. The petition 40to60RH points to the growing body of evidence linking relative humidity levels outside the “optimal” 40-60% range to increased incidence of respiratory disease. In the future, the incorporation of smart indoor air quality control systems into new build homes could have far-reaching consequences for our collective wellbeing.

Indoor air quality is a serious issue for public health.¹² There are clear guidelines for indoor air quality laid out by the World Health Organization and Environmental Protection Agency, and organizations such as ASHRAE are laying the foundations to integrate these considerations into our building practices.

We may soon see our indoor air quality taken as seriously as outdoor air quality, with a legislature that defines acceptable levels of pollutants in our homes, schools, and offices. When this happens, environmental sensing solutions and smart control systems will be crucial to ensure safe, clean air for everyone.

1. AQI Basics | AirNow.gov. Available at: https://www.airnow.gov/aqi/aqi-basics/. (Accessed: 11th August 2020)
2. Hayes, D., Collins, P. B., Khosravi, M., Lin, R.-L. & Lee, L.-Y. Bronchoconstriction Triggered by Breathing Hot Humid Air in Patients with Asthma. Am. J. Respir. Crit. Care Med. 185, 1190–1196 (2012).
3. Introduction to Indoor Air Quality | Indoor Air Quality (IAQ) | US EPA. Available at: https://www.epa.gov/indoor-air-quality-iaq/introduction-indoor-air-quality. (Accessed: 11th August 2020)
4. KLEPEIS, N. E. et al. The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. J. Expo. Sci. Environ. Epidemiol. 11, 231–252 (2001).
5. ‘Compelling’ evidence air pollution worsens coronavirus – study | World news | The Guardian. Available at: https://www.theguardian.com/world/2020/jul/13/compelling-evidence-air-pollution-worsens-coronavirus-study. (Accessed: 27th August 2020)
6. How humidity may affect COVID-19 outcome. Available at: https://www.medicalnewstoday.com/articles/how-humidity-may-affect-covid-19-outcome. (Accessed: 27th August 2020)
7. California wants to see how cooking with gas affects indoor air - Health - The Jakarta Post. Available at: https://www.thejakartapost.com/life/2020/05/09/california-wants-to-see-how-cooking-with-gas-affects-indoor-air.html. (Accessed: 11th August 2020)
8. World Health Organization Guidelines for Indoor Air Quality. (2010).
9. Improving Indoor Air Quality | Indoor Air Quality (IAQ) | US EPA. Available at: https://www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality. (Accessed: 11th August 2020)
10. Anderson, H. R., Favarato, G. & Atkinson, R. W. Long-term exposure to air pollution and the incidence of asthma: meta-analysis of cohort studies. Air Qual. Atmos. Heal. 6, 47–56 (2013).
11. Environmental Sensors | Sensirion. Available at: https://www.sensirion.com/en/environmental-sensors/. (Accessed: 11th August 2020)
12. Dales, R., Liu, L., Wheeler, A. J. & Gilbert, N. L. Public health: Quality of indoor residential air and health. CMAJ 179, 147–152 (2008).