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Clean air, year round.

by Haldane King

As of September 2022, office attendance is hovering around half of what it was before the Covid-19 pandemic. This has been met with mixed reactions from workers and employers alike, with a trend toward workers wanting to remain at home and bosses wanting them back in person. Regardless, the fact remains that we all will likely be sharing more breathing space with other people, and how we think about breathing space has fundamentally shifted over the past few years.

Though it took a global pandemic for the world’s attention to focus closely on what is in our indoor air, experts were speaking with growing concern about indoor air quality well before 2020. Employees are now demanding more visibility into the health of the building they are returning to. As a result, employers and facility managers are taking steps they probably should have been taking all along to prevent poor air quality from impacting workers’ health and ability to perform.

Anyone who works in a building should know the basics of when natural ventilation is enough for a healthy and productive indoor environment and when further steps need to be taken. Everyone should also be aware of some basic indoor conditions with all of the air quality sensors now available. Let’s take a look at how modern office buildings are and are not configured to keep the air free of the contaminants that tend to build up indoors.

Make sure you can see your air

The first step in addressing air quality issues is to use air quality monitors equipped with different sensors to measure your indoor environment. Some components of the air are invisible and need special equipment to measure, while others can be measured with cheap gadgets from the hardware store.

Gauges showing air pollutant levels

Air quality monitors available to the public can rarely be calibrated after they leave the factory, so tend to drift over time. Still, consumer sensors can measure overall air quality trends and are reliable for alerts when the air quality has shifted significantly worse or better. Managers of large facilities with many different floors and enclosed spaces usually use many sensors organized with an app or other centralized tool.

Indoor conditions are influenced by the weather and sunlight outside, which changes with the time of day or year. Just glancing at the air quality a few times a day may not be enough to know if there is an issue. Along the same lines, detecting more pollutants makes it easier to narrow down the source of problems. An air quality monitor that can show readings over time and can detect multiple air quality conditions will be most effective.

Ventilate, purify, or both

During the early stages of the pandemic, precautions to reduce the amount of Covid-19 virus particles already in the air took many forms, but at this point has settled down to two key methods- ventilation and portable air purification. There are two types of ventilation, and they are often combined in the same space: mechanical ventilation that uses HVAC or similar powered devices to move air through vents, and natural ventilation like open windows that allow air to move in and out according to its own whims.

Vector art showing air flow through an office room

Ventilation can be effective for many indoor air quality problems because outside air is usually free of the pollutants that build up indoors, and it is readily available. Getting a similar amount of clean airflow with portable purifiers can require more electricity and space.

The big drawback is that ventilation interferes with environmental controls in the building. Money spent on electricity for air conditioning, heating, or humidity will literally go out the window. Another disadvantage is that contaminants must flow through the breathing area of other occupants before they are gone.

Vector art showing Molekule air purifier protecting against airborne viruses in office

Portable air purifiers don’t impact indoor environmental controls so are more energy-efficient when considering the whole building. With a portable purifier, “Clean Air Zones” can be established for common breathing areas. However, different purifiers remove different pollutants at different rates, and some common pollutants cannot be practically removed and must be ventilated.

"Air purifiers can help reduce risk of exposure to virus particles in the air, but no air purifier can fully prevent transmission of a virus.”

Know the most common indoor air quality issues

The feeling of stale air is actually a combination of chemicals that build up in occupied spaces. Building materials, moisture, breathing, and each person’s unique combination of bioeffluents contribute to the feeling of a room being stuffy or uncomfortable, which often means unhealthy as well. Here are seven of the most common culprits behind bad indoor air quality, how to monitor them, and if ventilation or purification is the best solution.

Vector art showing CO2 buildup between two office workers

1. Carbon dioxide

Carbon dioxide (CO2) is a gas that results from burning fossil fuels and from human respiration, so it is an indoor pollutant we are all constantly exposed to. While climate scientists are working hard to stop the impact of outdoor CO2 in the coming years, indoor CO2 is impacting us today. In occupied conference rooms or crowded spaces levels of CO2 can easily get high enough to impact cognition and productivity

  • Carbon dioxide sensors are inexpensive and easy to find. They are best placed anywhere people congregate for 30 minutes or more.
  • Normal outdoor CO2 is around 400 ppm, and decision making can be impacted at levels around 1000 ppm and significantly so at 2500 ppm.
  • Ventilation is effective in reducing CO2 because the outdoor concentration will always be preferable to indoors.
  • Air purifiers do not have an impact on CO2, there are no filters available to consumers that can remove it.
Vector art showing PM 2.5 and PM 10 particles surrounding a person

2. Particles

Particulate matter (PM) is any small fragment small and light enough to stay afloat in the air. Many of these particles pick up other pollutants as they travel, and as a result may be the most significant air quality threat. Larger particles (PM10) like whole mold spores or road dust are more easily caught by the lungs and pushed out, but fine particles (PM2.5) from smoke or from aggregated chemical pollutants can penetrate deep into the lungs and enter the bloodstream

  • Particle detectors are relatively inexpensive. Most differentiate between large (PM10) and fine (PM2.5) particles, and often come in devices that include other air quality sensors. All buildings should have particle detectors where people are spending long amounts of time.
  • According to the WHO, an ideal fine particle (PM2.5) concentration is under 5 ug/m3 on average, allowing for spikes of no more than 15 ug/m3 for 24 hours. Large particles (PM10) should be kept under 15 ug/m3 on average and no more than 45 ug/m3 for 24 hours.
  • Ventilation is effective in reducing particulate matter when the source is indoors.
  • Air purifiers can be effective in reducing particulate matter from any source, though they particularly vary in effectiveness in removing fine particles. Purifiers with true HEPA filters are the industry standard for removing fine particles.
Illustration of paint can, nail polish, and diffusers, labeled "VOCs"

3. Organic chemicals

Organic chemicals (VOCs) are a large group of substances that tend to become gas at room temperature. The potent scents from fresh paint, new carpets, scented cleaning products, plastic manufacturing facilities, and dry erase markers are all examples of VOCs. When VOCs react with ozone in the air, they can form fine particles.

  • TVOCs sensors detect the total amount of VOCs in the air, are inexpensive, and tend to come bundled with other sensors. Keep in mind that TVOC sensors detect harmful VOCs in the same reading as harmless VOCs from scents or open bottles of wine. Still, consistently high levels of any VOC can lead to fine particle formation in the air. Areas where people spend long amounts of time should be monitored for VOCs.
  • Research is still being conducted on the impact of VOCs, but keeping TVOC under about 500 ppb or about 0.5 mg/um3 can be considered safe. However for specific VOCs that are highly toxic or carcinogenic such as benzene, these levels would be on the border of unsafe.
  • VOC identification testing is typically done at a lab with specialized equipment run by experts, so knowing which VOCs are in your air is not usually an option. The EPA maintains a list of VOC sources and which are more concerning than others. VOC identification testing is usually only useful when there is concern about a specific highly toxic VOC.
  • Ventilation is effective in reducing VOCs when the source is indoors.
  • Air purifiers can be effective in reducing VOCs from any source, but vary in effectiveness. Purifiers that use large amounts of activated carbon will likely be effective in removing VOCs. Molekule’s solution, PECO, actually captures and destroys VOCs.
Vector art of allergens, including a flower, pollen, and plants

4. Allergy and asthma triggers

Allergy and asthma triggers overlap in many ways but are slightly different. An allergy is a reaction to a foreign substance, usually one that is biological like pollen, pet dander, dust mites, or mold spores. While most allergy triggers are also asthma triggers, airborne asthma triggers also include respiratory irritants that don’t necessarily cause an allergic reaction like tobacco smoke, bleach, or ammonia.

  • Airborne allergy and asthma trigger sampling and testing is expensive and will just tell you what is in the air, not if you are allergic or to what degree. It is easier to see an allergist to find out what you are allergic to and take precautions to avoid it. Pollen is best handled by preventing outdoor air from coming in. Dust or pet dander is best handled by vacuuming and dusting. Mold can grow in hidden places and if discovered may require professional remediation.
  • Ventilation should be used with caution to reduce allergy and asthma triggers, only when it’s clear that there is an indoor source that is airborne. Mold spores and pollen often come from outdoors, so any incoming air needs to be filtered or risks making air quality worse.
  • Air purifiers can be effective in reducing allergy and asthma triggers. Air purifiers have the potential to reduce the level of allergen particles in the air, regardless of their source, before they are inhaled. Unlike windows or HVAC vents, they can be easily placed throughout a room to add a layer of protection.
Vector art of pathogens such as viruses and bacteria

5. Airborne pathogens

Some viruses and bacteria are airborne pathogens that can cause various diseases. Each breath of air that is shared with an infected person raises the risk of contracting the disease. 

  • Airborne pathogen sampling and testing is typically very expensive, time consuming, and can only look for certain pathogens. It can be helpful in confirming the presence of specific bacterial diseases that grow in buildings such as Legionella, but can’t help any occupants during exposure. Airborne pathogen sampling and testing is best saved for the experts.
  • Ventilation is somewhat effective in reducing airborne pathogens. Most ventilation systems were designed for climate control, not air quality. If not configured to reduce infections, some move air from room to room which studies suggest spreads infectious virus or bacteria particles. Ventilating with open windows reduces this issue but people closer to the window will be breathing cleaner air than those deeper in the room.
  • Air purifiers can be effective in reducing airborne pathogens. Viruses in particular are extremely small, but can be trapped by high-efficiency filters like HEPA. Some purifiers, such as Molekule with PECO filters, can also destroy pathogens to add another layer of protection.
Scale showing varying levels of humidity

6. Relative humidity

Moisture or relative humidity (RH%) is a gauge of water content in the air and needs to be in a specific range, ideally 30% to 50%. Sources of indoor humidity  can be leaky pipes or just the use of an electric kettle, and humidity can drop when either air conditioning or heating is used. Excess humidity is of particular concern in large buildings where there are many hidden spaces like HVAC vents for mold to grow undetected. Too little humidity can dry out our noses and throats, weakening immune defenses and increasing the risk of infection.

  • Relative humidity gauges are cheap and available. One that integrates with an app or other service to track humidity over time can be more useful. Relative humidity should be tracked on every floor at minimum.
  • Ventilation will slowly change the humidity to that of the outdoor humidity, which may or may not be desirable, but can’t be controlled if not.
  • Air purifiers do not have an impact on humidity, there are completely separate devices called humidifiers that increase humidity and dehumidifiers that decrease humidity.
Scale showing varying degrees of temperature

7. Temperature

Temperature is another factor in air quality. Most people prefer indoor  temperatures between 17°C/ 63°F and 28°C/ 82°F. When controlling temperature keep humidity in mind because the use of either air conditioners or heaters leads to a drier indoor space.

  • Thermometers that can report the temperature over time are fairly common and easy to get. Temperature should be monitored wherever there are people or environmental controls.
  • Ventilation will quickly interfere with any heating or air conditioning, and risks wasting utilities as a result.
  • Air purifiers do not have any impact on temperature.

The take-out messages

There are a few different ways we can use the new focus on indoor air quality to our advantage. Ventilation is an acceptable primary solution, but many buildings don’t have enough. One expert estimates that individual productivity could be increased by an average of $6,500 a year if ventilation were doubled, and notes that “does not include other potential health benefits, such as reduced sick building syndrome and absenteeism” But it’s not as simple as just opening everyone’s window, in some conditions air purifiers could work better while in others controlling the source is the best option.

  • Ventilation is vital to remove unavoidable carbon dioxide from occupied spaces.
  • Ventilation to reduce other pollutants should be balanced with climate control to save on utility costs.
  • Portable air purifiers, when placed strategically, can reduce particles, allergy/ asthma triggers, pathogens, and VOCs without impacting climate control.
  • Everyone responsible for or inside the building should have access to a historical report of PM10, PM2.5, TVOC, CO2, relative humidity, and temperature for occupied areas.
  • Finding out which specific VOCs, allergy/ asthma triggers, or pathogens are present in your indoor air is rarely worth the expense.


Molekule made Air Pro with these issues in mind. It was designed to capture particles and destroy VOCs, ozone, and pathogens. Air Pro’s Auto Protect mode automatically reacts to changes in pollutant concentrations to keep the right balance of air quality and noise. The sensor suite detects large particles (PM10), fine particles (PM2.5), and micro particles (PM1), TVOC, CO2, relative humidity, and temperature. Then the 28-day view on the Molekule app can tell you when and where air quality issues might be happening.


Stay tuned to our Facebook, Instagram, and Twitter account and the Molekule blog for more tips on how to breathe cleaner air.

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