Workplace AQ Monitoring

Measuring Indoor Air Quality: Creating a Better Workplace Environment through AQ Monitoring

Image Source: Girts/stock.adobe.com

By Alex Pluemer for Mouser Electronics

Published May 24, 2023

Air quality indices (AQIs) have become a regular feature of weather reports worldwide as climate change continues to heat the planet and incite wildfires in hotter, drier climates. AQIs report the amount of particulate matter (such as ash and automobile exhausts) and other pollutants in the air, informing people when those pollutants reach dangerous levels of concentration for human exposure. AQIs are commonly used to describe the quality of the air outside, but what about indoor air quality?

Unhealthy outdoor air quality conditions can often be detected without technology (for example, visible smoke in the air or a strong odor), but poor indoor air quality isn’t as easily detectable. If you spend most of your day inside your home, a school, or an office building, the quality of the air indoors is more likely to affect your health than the air outside.

While polluted air from the outside can impact indoor air quality, several common indoor air pollutants can be detected and quantified only through air quality monitoring technology. Contaminants such as carbon monoxide (CO), secondhand smoke, and airborne mold or bacteria can lead to serious health ramifications through repeated exposure. The health and safety of employees and students are the primary responsibilities of any corporation or institution, and monitoring indoor air quality is an essential part of maintaining a healthy and safe indoor environment.

Air pollution is a severe problem that can have harmful effects on human health, particularly when it comes to indoor air quality. Fortunately, engineers and developers have been working to develop AQ sensors that can detect these pollutants and help promote a healthier workplace environment. This article will explore the different types of airborne contaminants that these sensors can monitor and why indoor air quality is important for overall workplace health and productivity.

Measuring Air Quality

As noted above, the most common airborne pollutants are particulates—microscopic particles of solid matter, often resulting from combustion—that we often inhale without awareness. When the air outside is highly saturated with particulates, people may be advised to stay indoors with the windows closed or to wear respiratory masks if they must be outdoors for extended periods. Many homes, schools, and office buildings implement air filtration systems to sift out particulate matter from the air. Still, small amounts of particulate are always present (outside of a clean room environment). 

Interior air quality is often compromised by other airborne pollutants that can cause serious health problems if they're not appropriately monitored. High levels of CO in the air can result in severe illness, unconsciousness, or even death. CO-related illnesses and deaths are commonly associated with using heating equipment or other appliances that burn fossil fuels; incomplete combustion creates an invisible, odorless gas that can build up in buildings and structures without adequate ventilation.   

Carbon dioxide (CO₂) levels in the air must also be monitored. Although the adverse effects of CO₂ exposure typically aren't as severe as those associated with CO, they can have long-lasting ramifications. People in CO₂-rich environments are often drowsier than normal and can experience headaches and nausea. Currently, 38 U.S. states and the District of Columbia require CO/CO₂ detectors in all private residences via regulation or legislation, but only five states require them in school buildings. CO poisoning usually occurs in minimal, enclosed environments, so CO monitors often aren't required in larger office buildings or manufacturing facilities.

Mold and mold spores are other common forms of airborne pollutants, typically resulting from humidity—and they aren’t always easy to find. Homeowners and facility managers can take preventative measures against mold growing in hard-to-reach spaces by monitoring interior humidity and condensation levels. Excess moisture can also cultivate certain airborne bacteria that can harm humans, providing another reason to closely monitor indoor humidity levels.

Volatile organic compounds (VOCs) are present in outdoor air almost anywhere where people live or work, but they are typically more highly concentrated indoors. VOCs are gases emitted from chemicals or other liquid or solid substances. They are present in a variety of goods, from cleaning supplies and paint to office equipment and furniture materials. Lowering the risk of VOC exposure is usually a matter of adequately storing hazardous materials and improving overall airflow and ventilation. Still, even low concentrations of certain VOCs (such as formaldehyde) in the air can be unhealthy.

Carcinogens like radon and asbestos can also be detected in structures built with materials that have since been widely prohibited for safety reasons. Although the adverse health effects of prolonged exposure might not be as immediate as those from CO exposure, they can be just as serious and even deadly. Both radon and asbestos exposure have been determined to increase the chances of developing lung cancer.

Air Quality Monitoring Technology

Air quality monitors aren't one-size-fits-all; they're available in different form factors and with various features and functionality. Depending on the installation location and environment, it may be beneficial to have a smaller AQ monitor. However, the smaller monitor may sacrifice functionality. Additionally, most AQ sensors can detect only some airborne pollutants, requiring a combination of sensors to detect everything.

Some AQ monitors use a tapered element oscillating microbalance (TEOM) to measure the levels of airborne particulate matter. These devices feature a hollow glass tube with an aperture on one end just large enough to allow microscopic pieces of particulate to enter. When particulate matter accumulates inside the tube, it oscillates, and the frequency of those oscillations increases as more particulate matter collects inside the tube. The size of the aperture is fixed, however, meaning a TEOM can measure only particulate matter that is smaller than the size of the aperture, which is somewhat limiting. Particulate matter can also be detected and measured optically using photodetectors, which measure the amount of light reflected off particles in the air. This method works with particulate matter of all sizes, as larger particles reflect more light than smaller ones.

AQ monitors detect gases like CO and CO₂ by using non-dispersive infrared light absorption. When infrared light passes through a gas, some is absorbed. By emitting infrared light through a space and then measuring that light's intensity on the other side, AQ monitors can determine how much CO and CO₂ (in parts per million) is present in that space.

Measuring VOCs in the atmosphere isn't quite as simple, as they can't be accurately measured without separating them from other elements in the air. This is usually done through a chemical process called gas chromatography wherein a sample of the air is mixed with an inert gas (commonly helium or nitrogen) and passed through a column or tube. Individual chemical components pass through the column at different rates according to their physical or chemical properties (or both), allowing the monitor to measure them separately.

One of the potential drawbacks of AQ monitors is the time it takes their sensors to calibrate to the implementation or environment—sometimes taking up to a month. As a result, any data gathered to that point may be inaccurate.

Another potential drawback is information overload, as AQ monitors operating 24/7 collect massive amounts of data. A single AQ in continuous operation that takes readings once per second will produce over half a million data points weekly.

Some AQ monitors on the market have built-in digital displays, while others are configurable only via an app on a computer or smartphone. Some are pre-programmed to work with digital home assistants (like Alexa or Google Assistant), smart homes, or building networks. Cost is also a factor; some industrial AQ monitors retail for several hundred dollars, but AQ monitors designed for homes or residences are available for under $100.

Air Quality, Health, and Productivity

Although no federally or internationally recognized standards currently exist for healthy air quality, agencies like the U.S. Environmental Protection Agency (EPA) and the Center for Disease Control (CDC) have helped create a set of recommended guidelines for safe exposure levels to the most common airborne pollutants. Airborne chemical pollutants like CO and CO₂ are measured in parts per million (ppm). CO₂ levels of 400–650ppm are considered normal for indoor environments, whereas levels of 800ppm or above may start to cause adverse effects. High levels of CO₂ in the air aren't just bad for your health—they can have severe ramifications for workplace productivity.

If you've ever been in a crowded, stuffy room, you may be familiar with the feeling: Your eyelids start to get heavy, the other voices in the room become background noise, and you drift off into a daydream. The meeting may have been boring, but you may have also felt the effects of CO₂ overexposure. Studies have demonstrated that CO₂ levels in the air directly correlate with workplace productivity and morale; that is, better ventilation equals happier, harder-working employees. By this logic, casinos monitor CO₂ levels to ensure their patrons aren't getting too tired—even pumping oxygen into the building to energize them.

Other airborne pollutants are safe only in minuscule concentrations (like formaldehyde, with recommended exposure levels no greater than 0.2ppm) or are unsafe at any level (like radon or asbestos fibers). Particulate matter in the air is measured in micrograms per cubic meter (µg/m³). The EPA recommends that PM2.5 (pieces of particulate matter with a diameter no greater than 2.5 micrometers) levels stay below 12µg/m³ and PM10 (larger particulates with a diameter of greater than 10 micrometers) remain at or below 54µg/m³, as larger pieces of particulate matter are easier for human lungs to filter out of our air than smaller ones.

Keeping heating, ventilation, and air conditioning (HVAC) systems operating at optimal levels also helps prevent the transmission of airborne diseases like COVID-19, saving companies time and money lost to sick days and reduced productivity. AQ monitors that can detect airborne pathogens aren't widely commercially available, but monitoring airborne pollutants like CO₂ can help improve overall airflow and ventilation and reduce the risk of disease transmission.

Conclusion

Monitoring indoor air quality is crucial for promoting a safe and healthy working or learning environment. Air quality monitoring technology has made significant strides in recent years, allowing us to detect a wide range of airborne pollutants that can have serious health ramifications through repeated exposure. While outdoor air quality can often be detected without technology, poor indoor air quality is not always easy to see, making monitoring critical. We can improve overall airflow and ventilation by keeping HVAC systems operating at optimal levels and reducing the risk of disease transmission, resulting in greater productivity and better workplace morale. As technology continues to evolve, we can expect even more advanced air quality monitors to detect a wide range of pollutants and help ensure that indoor environments remain safe and healthy.