indoor air quality

The 2021 guide to Indoor Air Quality Monitoring (IAQ)

A business analysis of indoor air quality standards and viral prevention

This document is for operations personnel and businesses new to indoor air quality monitoring. It breaks down a range of common concerns and recommends practical, low-cost solutions that companies implement and offer to their customers.

From reduced productivity to getting sick to ultimately becoming indisposed 一 there’s a common thread to it all, and it has a cost. Investing in understanding IAQ is an investment in your people and data around how a building serves them, with a substantial ROI.

The primary information throughout this document is academically confirmed and available for reference at the bottom.


America’s domestic state of affairs

In 2020, the world became systematically educated on the impact airborne viruses have on our communities. Concern over healthy air quality became nationally normalized by the Centers for Disease Control and Prevention (CDC) as a primary prevention measure. Consumers now have expectations about indoor air quality and evaluate the physical spaces they spend time in. The most affected industries include airlines, assisted living centers, and schools.

That said, even before COVID-19, the Environmental Protection Agency (EPA) estimated that poor IAQ was negatively impacting 33% to 50% of industries in the U.S.

Moreover, America’s domestic environment has become increasingly volatile in recent years, with wildfire smoke, smog, and growing quantities of chemical and biological pollutants congesting our atmosphere. Buy-in to improve local air quality is now being pressed (to varying degrees) at the national, state and municipal levels, prompting new commercial investment in measuring and controlling IAQ.

The Indoor Air Quality solution market

While helpful solutions to measure and manage IAQ exist, there is a rapidly increasing amount of new insights being brought into the market. With discussion around IAQ becoming mainstream in the U.S. and an overwhelming amount of information available, how to ensure healthy IAQ within buildings is a question many businesses are asking and vetting individually. Predominantly, monitoring indoor air quality environments is seen as the most reliable and effective.

What about IAQ filters and purifiers?

Air filtering is where most businesses start on their journey. Engineered filters and air purifiers can be highly effective in filtering out contaminants, pollutants and particles containing airborne viruses. HEPA filters are broadly considered the standard in the United States and commonly used in major industries.

Unfortunately, in addition to being an expensive solution, even HEPA filters are not recommended as a first-line defence by the CDC because of their questionable effectiveness to capture the viral particulate matter in an environment (including coronavirus) before it spreads from person-to-person. This gap in managing air quality is why we still hear about the coronavirus spreading in places where HEPA filters and air purifiers are commonly used, such as airplanes and hospitals.

The role of a BAS or BMS system

Sometimes larger and newer buildings, particularly within the enterprise and public sector, will have large-scale building systems (BMS or BAS) to control equipment and monitor conditions like humidity, temperature, water leaks etc. Unfortunately, again, robust IAQ measurement and monitoring is something regularly outside of their capabilities. Moreover, BAS and BMS systems can cost hundreds of thousands of dollars to implement (and in excess of $1,000 for each point they monitor), making it impossible for 80% of America's buildings to expect an ROI.

How have costs recently changed in IAQ monitoring?

When it comes to IAQ sensors, most retro-fit solutions require a lot of new cabling to provide power and network from each sensor to a home network and other network hardware that makes start-up very expensive and difficult to obtain any ROI.

More recently, in the past two years or so, LoRaWAN wireless network technology has reduced the cost to about 1/10th of all previous solutions. LoRaWAN installations are also often up and running in hours, non-disruptive and can be set-up by non-technical staff.

Modern cloud software and analytics further reduce many of the existing technical restraints and associated costs by providing new building insights with less raw sensor data (e.g. using just temperature and humidity readings to determine mold growth risk). The software also offers comprehensive alarm automation, historical trends and dashboards that non-technical staff and low-salaried staff can manage.

Understanding and implementing indoor air quality monitoring solutions

Our team has diligently consulted with industry experts, reviewed data across academia, and scoured the web to help clients weed through the scientific complexities and marketing jargon related to indoor air quality. The result is a list of the most important practical and actionable insights.

The top concerns buildings should attend to are organized into the three individual sections below. Important but less common IAQ subjects follow that for completeness. Most clients have specific IAQ goals in mind and often consider multiple points into their final solution.

Concern Sensor
Occupant comfort
Temperature and humidity
Air ventilation and distribution CO2
Coronavirus and other viruses that disseminate via bioaerosols PM 10, 2.5, 0.3

We’ve also field-tested a broad range of wireless sensor vendors and included recommendations in each section on the most practical and cost-effective to choose from when implementing that IAQ solution.

1. Occupant comfort

 Temperature and humidity

Understand the specific conditions room-to-room to ensure each space is comfortable for all manner of occupants. 

While every building manages temperature, thermostats regulate the temperature only in the immediate area they're located. A surprising amount of space occupied by clients in a building is unmanaged and not optimal.

Less common for buildings is to be cognisant of their internal humidity levels. Understanding humidity is particularly crucial during a pandemic, as maintaining humidity above 40% is shown to play an important role in decreasing viral infections among occupants. Simultaneously, maintaining humidity below 80% can prevent mold and other biological contaminants from thriving within a building.

To keep occupants comfortable and healthy indoors, the CDC recommends temperatures should be targeting between 68.5°F and 75°F in the summer and 75°F to 80.5°F in the winter. At the same time, humidity should do its best to maintain between 40% - 65%. 

Recommended sensor
lorawan machineq temperature and humidity sensor

  MachineQ Temp and Humidity

lorawan sensative strips temperature and humidity sensor

  Sensative Strips

The same temperature and humidity sensors from this solution can be used in the Solve™ mold growth risk detection solution.

2. Air ventilation and distribution


Understand which indoor environments are overly congested, impair occupant cognition &  breathing, and correlate with increased viral risk.

What to monitor

In simple terms, carbon dioxide (CO2) is a gas exhaled when people breathe. Since people are the primary contributor of CO2 inside buildings, a buildup of the gas is a strong indicator of inadequate ventilation within a space. CO2 buildup is typically common within older buildings, where air distribution and capacity have become out-dated, usually due to changes in building use, previous renovations, or degradation of HVAC equipment.

How to benefit from CO2 data

With insight into CO2, building managers can easily see where better ventilation is needed. Along with proper building temperature and humidity levels, improving ventilation has been shown to boost decision making scores by 100%, and cut sick days by 55% (four days per person per year).

Insight into CO2 also helps buildings understand which of their spaces are presently vacant or occupied and how the space is used over time. This provides buildings with new options to optimize their ventilation to occupancy and historical trends, creating savings in building energy costs. It also enables building managers to provide evidence-based work orders for HVAC changes and maintenance.

CO2 data also has an emerging use in viral prevention. As more people occupy a space and share the surrounding air, CO2 inevitably increases and can correlate with an increase of viral load and transmission. As a result, CO2 can act as a proxy for potential viral load in a particular area within a building.

According to the National Institute for Occupational Safety and Health (a department within the CDC), CO2 concentrations should be no greater than 700 ppm above the current outdoor conditions. Since outdoor CO2 concentrations usually range between 375 - 500 ppm, this would suggest indoor CO2 below 1200 ppm is suitable for the large majority of occupants; however, most sources observe CO2 below 1000 ppm as an optimal target. 

Recommended sensor
lorawan elsys co2 sensor

  Elsys CO2

Solve™ provides a low-cost solution to gain insight into your HVAC units runtime and cycling.

3. Coronavirus and other viruses that spread via bioaerosols

PM 10, 2.5, and 0.3 mass concentration

Understand when air quality is ripe for viral transmission between people.

Airborne viruses

Overwhelmingly evidence has shown that airborne viruses, including coronavirus, most actively spread between people by attaching to particulate matter (PM) or droplets produced when an infected party talks, sneezes or coughs. These droplets are often referred to as "bioaerosols".

Once expelled by an infected person, bioaerosols can stay suspended in the air for a few minutes to a few hours, significantly increasing the inhalation risk by a non-infected person.

How does this relate to the coronavirus (COVID-19)?

Empirical and clinical evidence with contact tracing shows that, like many airborne viruses, COVID-19 does not spread widely through touch. When bioaerosols carrying the virus do get onto a surface, it is often through a sneeze or cough first spreading into the surrounding air. This understanding of how airborne viruses disseminate makes IAQ monitoring a primary line of defence.

Early evidence also points to the coronavirus being able to better sustain in room temperature (68°F) and colder environments (e.g. cold storage), rather than warmer climates we might experience outside (upwards of 86°F). For example, in a laboratory setting, the coronavirus can sustain on most room-temperature surfaces for four weeks.

PM10 vs. PM2.5 vs. PM0.3 for viral monitoring

Bioaerosols with a diameter of 10 micrometers (PM10) or less are small enough that they can be unknowingly inhaled by building occupants. Those bioaerosols of 2.5 micrometers (PM2.5) or smaller pose the most significant risk to human health. Bioaerosols of this size can travel distances beyond six feet, stay suspended in the air for more extended periods, and, when inhaled, can embed deep into the bloodstream. PM2.5 sensing technology provides a practical approach for most building operations and is widely recommended.

When detecting bioaerosols associated with the coronavirus and COVID-19, the recommendation is to use enhanced concentration detection down to 0.3 micrometers (PM0.3). PM0.3 sensor technology is now available and does serve some obvious and specific purposes regarding occupant safety. However, PM0.3 solutions are not able to continuously monitor an area in the same way as PM2.5 sensors are. PM0.3 sensors are suitable for specialized use-cases, providing a precise measurement at a moment in time rather than functioning as an ongoing monitoring solution.

PM2.5 detection is considered the EPA's standard, which sets a 35 micrograms per cubic meter (μg/m3) daily upper limit and 12 μg/m3 yearly average.

Recommended sensor
lorawan machineq pm2.5 sensor

  MachineQ PM2.5

senseware pm0.3 sensor

  Senseware PM0.3

Airflow awareness

Monitoring airflow within specific areas of a building also plays a critical role in controlling indoor air quality. Maintaining sufficient positive or negative pressure in particular building areas determines where the "good air" and "bad air" flows.

With positive-pressure areas, clean air is pushed into a room and naturally flows out, generally outside the building. Positive pressure areas keep the "bad stuff out" and is the most common objective.

Correspondingly, negative-pressure areas ensure contaminated air in a specific area does not spread to the other areas of the building via the HVAC system. Negative pressure areas or rooms are used to contain a viral infection, such as a COVID-19 isolation room, dangerous gases like carbon monoxide in garages, and similar cases.

Measuring the air pressure differential on both sides of an air filtering system will indicate when the filter is "loaded" and should be replaced.

Less common indoor air quality concerns

Below, our team has also gathered information on other less common IAQ concerns some clients may have. Contact us if you’d like to learn more about monitoring any of them. 

Commonly alarmed conditions

Universally monitored conditions, such as fire smoke and carbon monoxide, are well established and often regulated and, as such, are excluded from the scope of this document.

Chemical and biological contaminants


Volatile organic compounds (VOCs) refer to thousands of different chemically and biologically produced compounds that can occupy our air, hundreds of which can be created by simple household items. Typically, an excess of these compounds can cause short or long-term health risks.

Generally, when it comes to indoor spaces, VOCs are introduced via toxic materials used during building construction or maintenance, such as cleaning products, glues, paints, varnishes, and wood/plastic composites. Biological compounds, such as bacterias and molds, can also travel from the outdoors into buildings and pose their own set of problems.

Greenhouse gases

CO2e, CO2eq, eCO2

Carbon dioxide equivalent (CO2e) is a metric measure used to compare the amount of CO2 within various greenhouse gasses that would have the equivalent global warming impact. CO2e has largely become the standard in which other greenhouse gases are compared, translated into a common unit.

Some sensor manufacturers offer CO2e as a relative indicator of CO2 at a less expensive price than a real CO2 sensor. They calculate CO2 using VOC measurements then make assumptions about the percentage of CO2 compounds in the air.

Regulated or site-specific needs

Radon, formaldehyde, and ozone

Radon, like many of the most hazardous gasses, cannot be smelt, tasted, or seen, and is estimated by the EPA to be responsible for over 20,000 lung cancer deaths each year within the U.S. Radon can primarily enter and congest buildings through air pressure differences in underlying soil and groundwater, creating a suction effect for radon to enter through cracks in the foundation. Radon is particularly problematic for older buildings that may have built up more cracks and crevices throughout its lifetime.

Formaldehyde is a colorless, highly toxic, and flammable indoor gas and is one of the most commonly detected VOCs. Like most VOCs that find their way into indoor spaces, it is regularly expelled into the air through common building materials, such as paper, plywood, resins, dyes, glues, fertilizers, disinfectants, and preservatives.

Ozone (O3), like the others, is also usually colorless; however, it does carry a pungent odor. Because sunlight is important to its production, ozone is often more abundant in indoor spaces that receive a lot of sunlight and in the summer months. Ozone is used in many industries within the U.S., most commonly to treat and purify drinking water, waste treatment, oils, bleaches, and other chemicals that may leak from machines. Exposure creates headaches, heavy breathing, and coughing, and chronic exposure may lead to asthma development.

How we can help

Our product, Solve™, collects data from all onsite indoor air quality and other sensors across your buildings and applies intelligent analytics to monitor for atypical situations that indicate a space is unsafe or is costing the building money. 

When something needs attention, Solve creates a ticket for a building manager and notifies of the potential problem or risk so that it can be quickly assessed and resolved. Users also gain access to real-time dashboards and reports to visualize how things are performing at the moment and understand trends in a building over time.

Call to compare notes …

Allen, Joseph, Piers MacNaughton, Usha Satish, Suresh Santanam, Jose Vallarino, and John D. Spengler. “Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers: A Controlled Exposure Study of Green and Conventional Office Environments.” Environmental Health Perspectives 124, no. 6 (June 2016): 805-812.

Baron, Paul. “Generation and Behavior of Airborne Particles (Aerosols).” Centers for Disease Control and Prevention. Accessed October 14, 2020.

Brander, Matthew. “Greenhouse Gases, CO2, CO2e, and Carbon: What Do All These Terms Mean?” Accessed October 14, 2020.

Centers for Disease Control and Prevention. “Protect Yourself and Your Family from Radon.” Last reviewed January 29, 2020.

Centers for Disease Control and Prevention. “Radon in the Home.” Last reviewed January 30, 2020.

CO2 Meter. “CO2 Sensors vs. VOC Sensors for IAQ - What's the Difference?” Last modified January 13, 2012.

Environment and Climate Change Canada. “Air quality.” Last modified February 21, 2019.

Harper, Peter. “Assessment of the major hazard potential of carbon dioxide (CO2).” Health and Safety Executive (June 2011): 1-28.

Jayaweera, Mahesh et al. “Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy.” Environmental research vol. 188 (June 2020):109819. doi:10.1016/j.envres.2020.109819.

Medium. “InCar Air Quality — PM2.5 & VOCs.” Published June 5, 2018.

National Institute for Occupational Safety and Health. “Carbon Dioxide Exposure Effects – Fact Sheet.” Accessed October 14, 2020.

National Institute for Occupational Safety and Health. “Formaldehyde.” Last reviewed June 21, 2019.

National Institute for Occupational Safety and Health. “Indoor Environmental Quality.” Last reviewed September 1, 2015.

National Institute for Occupational Safety and Health. “Ozone.” Last reviewed June 22, 2019.

New York Times. “Can HEPA Air Purifiers Capture the Coronavirus?” Last modified July 9, 2020.

Ontario Secondary School Teachers’ Federation. “Inadequate Ventilation and High CO2 Levels.” Accessed October 14, 2020.

Riddell, Shane, Sarah Goldie, Andrew Hill et al. “The effect of temperature on persistence of SARS-CoV-2 on common surfaces.” Virology Journal 17, no. 145 (October 2020).

Senseware. “Airborne Monitoring.” Accessed October 14, 2020.

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Senseware. “Making Sense of Indoor Air Quality Metrics.” Last modified April 9, 2019.

U.S. Department of Energy. “Demand Control Ventilation.” Energy Efficiency and Renewable Energy. Created August 2012.

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World Green Building Council. “Doing Right by Planet and People: The Business Case for Health and Wellbeing in Green Building.” Accessed October 15, 2020.

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