University of Birmingham scientists have developed a new way of measuring and analysing indoor air pollution that - in initial trials - has established a clear link between office occupancy, physical activity, and air quality.
Using radar-powered movement detectors and low-cost pollution sensors, researchers equipped office space in central Birmingham to monitor the number of people present and measure the kinetic energy they generated as they went about their work.
Researchers say that using the Birmingham approach, engineers and architects would in future be able to create better designed and ventilated buildings.
One of the most important, yet insufficiently studied, sources of indoor air pollution is particulate matter (PM) that is made airborne through occupants' movements. Particulate matter trapped within carpeting, furniture, office equipment, and people's clothes and shoes becomes airborne in indoor environments through human activity.
Publishing their findings today (14 Jan) in npj Climate and Atmospheric Science, the researchers found that weekday concentrations of inhalable particulate matter one-fifth the width of a human hair – known as PM10 – were up to four times higher during occupied periods than during unoccupied periods. Other pollutants studied – carbon dioxide (CO2) and total volatile organic compounds (TVOC) – also showed elevated levels on working days, up by 22% and 140% respectively.
Occupied office periods averaged 13.7 µg/m³ PM₁₀, compared to 3.75 µg/m³ when empty. WHO's annual PM₁₀ guideline is 15 µg/m³. CO₂ rose by 130 ppm to 584 ppm and TVOCs rose by 318 µg/m³ to 495 µg/m³ indoors.
The University of Birmingham team worked on the new system – installed in an open plan office area and a meeting room – with counterparts from Queen Mary University London and experts from Cundall, an independent, global sustainable engineering and design consultancy.
By combining Birmingham's air-pollution expertise with Queen Mary University of London's radar-based sensing and Cundall's leadership in optimising indoor environments, the team has created a new way of understanding and designing healthier indoor spaces.
Co-author Francis Pope, Professor of Atmospheric Science at the University of Birmingham, said: "Government and industry are looking for evidence-based, low-cost methods to manage indoor pollution. Our study creates a new way of analysing and discussing indoor air quality that can be used immediately to help create better buildings for work, leisure and living."
Lead author Dimitrios Bousiotis said: "Using the number of occupants alone to estimate indoor air quality is not as effective as considering the kinetic energy they generate. Our approach will help to understand better how the size, design, and use of different office environments impact air quality when workers operate within them."
The deterioration of air quality is one of the most pressing issues affecting public health, as it can cause short term respiratory symptoms as well as longer-term issues leading to strokes, heart attacks, and lung cancer.
Jenny Carrington, from Cundall, said: "This new approach to analysing indoor air quality provides an affordable, easy-to-apply methodology that can help to better design cleaner and healthier indoor environments - improving people's quality of life, as well as the occupational safety and productivity of workers in offices and other indoor workspaces."
Dr Khalid Rajab, from Queen Mary University of London, said: "This study highlights the value of emerging sensing technologies – such as millimetre-wave radar – for assessing how human activities influence indoor air quality, and for helping to promote healthy living at home and in the office. This technology is particularly significant because it is unintrusive, uses no cameras or wearables, and preserves occupants' privacy."
Indoor air pollution is a major health concern since people spend up to 90% of their time indoors and pollutants can build up in the spaces where people live and work. The World Health Organization (WHO) estimates that out of nine million deaths attributed to air pollution, 3.2 million are linked to the deterioration of indoor air quality.
