Maintaining healthy air in offices in regions with high outdoor air pollution

Pooja Shukla

Feature image photo credit: Lightfield Studios from Adobe Stock.

Do you think you leave outdoor air pollution outside when you step inside your office building?

Unless buildings are equipped to filter outside air, outdoor air pollutants can enter the indoor spaces unchecked, becoming the most significant source of indoor air pollution.

View in the table below air quality measurements inside some office buildings in India (these measurements were taken as part of the study “Healthy workplaces for healthier people” by GBCI India and Saint-Gobain Research India).


Average outdoor level

Average indoor level

Recommended indoor threshold
per ISHRAE IEQ Std. 2019 (for Class A Buildings)


172 μg/m3


<15 μg/m3




<50 μg/m3



69 μg/m3

<40 μg/m3

In regions where outdoor air pollution is a concern, chances are that even when you are inside buildings, your exposure to outdoor air pollutants is much higher than what is considered healthy. However, the good news is that buildings can be equipped to shield occupants from outdoor air pollution to a great extent. With intelligent systems, the design and operation of buildings can maintain healthy indoor air quality (IAQ) even if the outdoor air is highly polluted.

Filter inhalable particulate matter entering the building from outdoors.

Chronic exposure to inhalable particulate matter (PM) affects both the lungs and the heart and can cause many serious health problems. Even at very low concentrations, particulate pollution can have adverse health impacts.

A quick calculation: A person spending about eight hours in an office with an average indoor level of PM2.5 and PM 10 as 142 µg/m3 and 324µg/m3 will be inhaling approximately 570 µg of PM2.5 and 1300 µg of PM10 in that amount of time (taking the breathing rate of a sedentary adult as 0.5 m3/hour).

Indoor PM concentrations can be maintained at healthy levels through adequate filtration of outdoor air. A recent study on Indian offices showed that well-maintained HVAC systems with fine filters (with a Minimum Efficiency Reporting Value, or MERV, rating of 13) are effective in bringing down the indoor PM concentration to healthy levels in most regions of India.

However, in locations where the outdoor PM pollution reaches extremely high levels (“severe” India AQI category) during certain times of the year, though this system will be effective in reducing the indoor PM concentrations considerably, it may not be sufficient. In such conditions, depending on the intensity and duration of high outdoor PM levels, additional portable fine filters should be installed in the office space to achieve healthy levels indoors.

Commit to regular maintenance.

If the HVAC system is not maintained regularly, air filters get clogged with dust particles. This can result in reduced outdoor air delivery inside the office space and lead to a buildup of indoor air pollutants like CO2, formaldehyde and volatile organic compounds (VOCs). Choked air filters are unable to remove the pollutants effectively, and they increase the HVAC energy consumption as well. To ensure continuous delivery of healthy air, specific maintenance schedules for the HVAC systems should be followed, and the filters should be cleaned and replaced per the manufacturer’s guidelines.

Avoid shutting down the outdoor air intake.

Sometimes, building operators shut down the building ventilation system to reduce the entry of outdoor air pollutants inside the space or to reduce the heating or cooling load on the HVAC system. However, shutting down the outdoor air intake will lead to an increase in the levels of indoor air contaminants and result in unhealthy indoor air. It is crucial to ensure adequate ventilation in the building at all times to maintain healthy IAQ. Indoor CO2 concentration, an indicator of ventilation adequacy of the space, should be continuously monitored by installing CO2 sensors at occupants’ breathing zone level to ensure that sufficient outdoor air is being delivered in the space.

Make sure you are not breathing outdoor traffic pollution inside your office.

The same study on Indian offices revealed that 67% of the offices had nitrogen dioxide levels higher than the recommended threshold. In buildings located near high-traffic areas, traffic pollutants like nitrogen dioxide, carbon monoxide and VOCs can enter the building through ventilation and infiltration. To remove nonparticulate traffic-related pollutants from outdoor air, chemical filters should be installed in the filtration system.

Make the invisible visible.

Poor IAQ is an invisible issue, as high levels of indoor air contaminants are largely unnoticed by the occupants. However, technologies and sensors are available that can continuously track the IAQ and highlight hidden issues. Continuous monitoring and real-time display of indoor air parameters will enable building operators to identify and resolve any issues that affect the IAQ and will also reassure building occupants about the safety of their workplace.

Careful design and operation of the building HVAC systems and performance tracking of indoor air parameters will ensure delivery of healthy indoor air inside office buildings, even in locations where ambient air pollution remains a concern for most of the year.

View the IAQ study

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