CO2 Measurement Contributes to Better IAQ

Modern CO2 sensors help serve as indicators to create safer and healthier indoor environments

By Justin Walsh

In the throes of a global pandemic, assuring a clean, healthy environment for those who work in and visit commercial, industrial, and residential buildings remains a crucial priority for facility executives and facilities management professionals. Despite COVID-19 cases beginning to drop as more people become vaccinated, with warmer weather on the horizon, questions about indoor air quality (IAQ), HVAC systems, and their effect on the spread of COVID-19 remain top of mind.CO2 measurement

In today’s environment, building ventilation is fundamental to maintaining healthy, comfortable IAQ and decreasing risks to our health. From irritation of the eyes, nose, and throat; headaches, dizziness, and fatigue; to respiratory diseases, heart disease, and even cancer, both immediate and long-term health concerns are, in many cases, being directly linked to IAQ.

Beyond health, safety, and comfort, IAQ also has a significant impact on productivity and cognitive ability. Studies from 2016 and 2017 found that breathing better air led to significantly better decision-making performance among participants who were exposed to increased ventilation rates, lower levels of chemicals, and lower carbon dioxide. To that end, building owners are increasingly investing in advanced HVAC equipment and technologies in an effort to improve IAQ. Building safety is a critical demand for an increasing number of tenants. Consequently, facilities management professionals who aim to attract and retain tenants in the future are going to have to demonstrate that their spaces are indeed safe in terms of IAQ.

Despite the ability to improve the comfort, health, well-being, productivity, and cognitive ability of building occupants, verifying that the designed rates of ventilation are being delivered properly and effectively remains a challenge.

Assessing Adequate Indoor Air Quality

There are a number of ways to measure IAQ, and the most common parameters that HVAC experts look at include the following:

  • Total volatile organic carbons (TVOC)
  • Particulate matter (PM)
  • Humidity and temperature
  • Carbon dioxide (CO2)

While there are numerous ways to classify VOCs, there is no good way to pinpoint and measure microbiological or chemical VOCs in a cost-effective manner. Additionally, measuring and distinguishing between various PM sizes and their total weight per given volume remains difficult. There are PM sensors available, but verifying data from such instruments remains challenging due to a lack of internationally recognized calibration and servicing standards. Finally, there are challenges associated with measuring temperature and humidity as a means of judging ventilation effectiveness because the supply air has either already been conditioned to the temperature, dehumidified or humidified, or mixed with outdoor air.

Even though such parameters may be able to give a general indication of IAQ by mapping trends over a period of time, the aforementioned challenges suggest facilities decision-makers will not be able to obtain a tight dataset from which they should base control decisions, especially not those made in real time. From TVOC and PM to humidity and temperature, chronic exposure to conditions of any of these parameters outside of the accepted range is going to impact IAQ—and our health and well-being—in the long term.

Measuring CO2 Levels Helps Inform Health Risks Related to IAQ

While there are numerous parameters used to evaluate a building’s IAQ, there is no real-time continuous measurement as proven and reliable as carbon dioxide (CO2) measurement. In fact, scientific studies are increasingly shifting away from the more attractive parameters like VOCs and PM concentration due to inaccurate measurements and a lack of quality data, instead examining CO2 as an indicator of IAQ.

CO2 measurements can be used as both a trigger to control ventilation and as a means to evaluate whether the proper ventilation rates are being delivered. The amount of carbon dioxide in a building is often related to how much fresh air is being brought into a building, and, generally speaking, higher concentrations of CO2 can be equated to a lack of fresh air being exchanged.

Because CO2 is emitted in commercial and office buildings by humans breathing and not by many other sources, it provides a good indicator of ventilation effectiveness and the IAQ in buildings where the occupants and their activities are the main source of pollution. Analyzing levels of CO2 in indoor air can reveal whether HVAC systems are delivering the ventilation and acceptable indoor air quality they were designed to achieve. Consequently, CO2 is most relevant as an occupancy indicator in rooms, such as offices, classrooms, etc., where the need for ventilation is linked to the presence of people.

For accurate and stable HVAC measurements, modern CO2 sensors provide stability and reliability over the long-term in a cost-effective manner. By mounting CO2 sensors on walls in spaces where ventilation is needed, facilities management professionals can rest easy knowing the measurement such instruments provide is not only accurate, but can be traced back to internationally recognized standards in order to maintain proper and healthy indoor air quality.

Even though CO2 measurement will not reveal the presence of respiratory droplets carrying the infectious SARS-CoV-2 virus (the virus that causes COVID-19), CO2 is a reliable and trusted parameter for the evaluation of ventilation effectiveness, thereby making it a key contributor to maintaining safer and healthier indoor environments.

As the world slowly gets back to pre-pandemic levels of normal, facilities management professionals will be making decisions that impact people’s lives, their health and safety, and their comfort, as well as the energy use in their commercial or residential building. Because CO2 measurement is a trusted method for helping inform the safety of an indoor space and indoor air quality-related health risks, advanced CO2 sensors can help make coming to the safest conclusion possible.

CO2 measurement

Walsh is a Business Development Engineer at Vaisala. He has been working with electro-chemical and industrial measurement technologies for over 17 years, ensuring product quality, measurement accuracy, and environmental safety. His experience includes application support with Thermo, environmental consulting, emergency planning and response with the US EPA, and a degree in Environmental Engineering from the Univ. of Miami.


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