Posted: 2/17/21

Indoor Air Quality and how it affects a building’s occupants has always played an important role in commercial building automation; but with the onset of Covid, the importance of monitoring and improving IAQ in a space was elevated to new levels.

Causes & Effects of Poor Indoor Air Quality

man painting

The internal causes of poor IAQ in a building, or space, are numerous and include: fumes from combustion appliances, tobacco smoke, off-gassing of building materials (asbestos, paint, flooring, other chemicals), cleaning products, personal care products, and many other sources. High temperature, relative humidity, and occupancy levels of a space can also contribute to poor indoor air quality; essentially the more people that are in a space the lower the IAQ. Inadequate ventilation or lack of demand ventilation also contributes to poor IAQ. Sources can also come from the outside in things such as pollen, radon, pesticides, smog, smoke, and other outdoor air pollutants.

man blowing his nose

Poor Indoor Air Quality can cause a plethora of short-term effects, including irritation of the eyes, ears, nose, and throat, fatigue, dizziness, exacerbation of conditions such as allergies, and increased absenteeism. Measuring and controlling IAQ is not only important for a building occupant’s comfort, but it also has the potential to mitigate the spread of bacteria and viruses. While there is no global standard for IAQ, several countries, states, and organizations have published guidelines for VOC (Volatile Organic Compound) measurement. Also, several US states have requirements or codes for CO2 measurement; California recently passed a law requiring CO2 monitoring in classrooms. Regulations are constantly changing, and new ones are emerging. 


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There are several solutions currently available to help improve IAQ, each coming with its own pros and cons. Air Cleaning and Disinfection via UV irradiation, Ionization systems, and other technologies can reduce viruses and bacteria in the air, but may not reduce CO2, other gases, or particulate matter. Adding or improving filtration in a building’s ductwork can remove dust, pollen, debris, and other particulate matter. However, it can put a strain on existing fans and motors, affect the building’s pressurization, and potentially lead to premature equipment failure or additional maintenance being needed. It also does not remove CO2 or other gases. Maintaining a proper RH level in your space can reduce the spread of microbial and potentially save energy. Increased RH levels may cause mold growth and some building materials may not be amenable to higher or lower RH levels. Also, if you are adding humidity to the space, the IAQ is only going to be as good as the water quality.

The easiest way to improve all aspects of Indoor Air Quality is to increase ventilation by bringing more outdoor air into the space. Increasing ventilation will improve levels of microbial, particulate matter, and gases such as CO2. Doing this can lead to higher energy costs as well as potentially higher equipment costs; so there is a balancing act between improving IAQ and energy efficiency. In many parts of the US simply adding more outdoor air to a building will lead to dramatically higher utility bills for most of the year. In short, there is no one-size-fits-all solution. However, in a post-pandemic world,  proving and documenting improvements to IAQ will be a way to encourage people to frequent public spaces such as offices, arenas, theaters, restaurants, and other facilities with a degree of confidence.


See our Application Diagram showing examples of locations for various sensors to monitor IAQ in a building

PM sensor
DLP with LCD
CO2 sensor


PM »

Differential Low Pressure »

Humidity »


CO2 sensor
Q5 B5 gas sensors

CO2 with Temp/RH »

ESENSE CO2 Series »

CO2 with Temp »

Q5/B5 Toxic/Combustible Gas »


Air Quality: Questions & Solutions Webinar

Since the onset of COVID-19 in early 2020, there’s been an industry-wide focus on Indoor Air Quality (IAQ) not just in terms of occupant comfort and energy efficiency, but also focusing on occupant health and safety. How can monitoring and controlling IAQ improve occupancy health? How do building owners encourage tenants and customers to return post-COVID? Learn about IAQ and the answers to these questions by watching our Air Quality: Questions & Solutions webinar, originally broadcast live on Feb. 11, 2021, and hosted by Brant Kasbohm.


California recently passed AB841, which requires CO2 measurement in classrooms.  ACI has several CO2 sensors to fit your application, including ones Compliant with AB841.

Link to article

Kids in class with masks

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