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Clean air, year round.

Molekule is happy to announce upgraded firmware for Air Pro that activates carbon dioxide, relative humidity, and VOC monitoring that pairs with an upgraded app that communicates air quality with a single score. Our hope is that this will give the public one more perspective on what is in their air.

Our engineering and product teams worked very hard to design a system that includes a particle sensor and a TVOC sensor (Total Volatile Organic Compound) which is simple but reflects the complexity of our atmosphere and its interconnected physical and chemical processes. To provide a meaningful understanding of how these processes impact what we are breathing, we first looked to the US EPA’s and how they provide easy-to-understand outdoor air quality information. This lead to the creation of the Molekule Air Score that integrates chemical and particle detection.

How to summarize the atmosphere

99% of our atmosphere is the non-toxic gas nitrogen and the oxygen gas we breathe. Most of the remaining 1% is argon, which is even less toxic than nitrogen. Science has found, however, that variations of gases at tiny fractions of a percent can have drastic consequences.

In studying the atmosphere, concentrations of gases in the atmosphere are often stated as so many parts per million (ppm) or billion (ppb), which is considering a variation of 0.000001% (one in a million) or even 0.000000001% (one in a billion). Such small concentrations may seem almost inconsequential until we consider their impact.

Our noses can detect some molecules in the air at concentrations of just a few ppb, and most of these are sulfur-based compounds that smell like decay or other potentially harmful sources. Strong smells like ammonia can usually be detected over about 5 ppm, or if the air is more than 0.000005% ammonia. Ammonia starts to become irritating at 100 ppm or 0.0001% and deadly at 2000 ppm or just 0.002%.

The growing climate crisis has highlighted the concentration of carbon dioxide in the atmosphere, which has increased from about 280 ppm to 410 ppm in the past 200 years or an increase of thirteen thousandths of a percent. This seemingly tiny change in proportion is projected to have dire consequences for our environment, including the possible extinction of more than half of the species on the planet.

The chemistry of the different components of the atmosphere varies quite a bit. The instruments used to detect changes in air quality not only must pick up incredibly small changes in concentration, they must also react to completely different substances. A sensor that is chemically sensitive to ozone, for example, can’t count particles of smoke in the air. And a sensor that can count particles usually can’t tell the difference between an infectious virus and a bit of soot.

As pollution has become more of a problem over the past century, the EPA and other organizations around the world have teamed up to study which components pose risks and what kinds of methods exist to detect them. They came up with the EPA criteria air pollutants and other air toxics that are continuously measured to provide the public with an idea of what is in the outdoor air.

The criteria pollutants are particulate matter (PM), nitrogen dioxide, sulfur dioxide, carbon monoxide, ozone, and lead. All of these pollutants are associated with burning fossil fuels, though lead pollution has largely been solved with the banning of leaded gasoline.

What is the EPA AQI

Each of the EPA’s criteria pollutants are toxic at different concentrations. So the EPA recommends a safe exposure level for each pollutant and anything over this level raises the risk of the associated health problems. Then, that recommended exposure level is used as the basis to translate the concentration of the pollutant into what is known as the Air Quality Index, or AQI.

The AQI tells the public how to react to ambient air quality at a glance. It is a color-coded intuitive numeric scale.

  • Green is 0 to 50 on the AQI scale, and considered clean air with minimal to no possible pollution impact and is under the recommended exposure level.
  • Over 50 to 100 is yellow and over the exposure limit but only people sensitive to air pollution like children or the elderly need to consider taking action.
  • 101 to 150 is orange, and the EPA recommends that all sensitive groups take action.
  • 151 to 200 is red and when pollution begins to have an impact on the general public.
  • Over 200 is purple and universally bad, while over 300 is maroon and a health emergency.
AQI chart


Whichever pollutant has the highest AQI will dominate. If the AQI for particulate matter from a wildfire is a yellow 80 but the ozone levels are an orange 130, then the AQI will be orange and shown as 130. Although it depends on the sensors available at the EPA air quality stations placed throughout the nation, usually only PM, nitrogen dioxide, sulfur dioxide, carbon monoxide, and ozone are used to calculate the AQI.

Indoor air quality monitors need to be different

The EPA criteria air pollutants were originally designed to satisfy requirements put forth by the Clean Air Act in response to the impact of outdoor fossil fuel usage many decades ago. Since then, research has discovered that not only are different pollutants present in indoor air, but they are present in greater concentrations.

While outdoor pollutants are always a concern because they continually seep into indoor spaces, indoor pollutants require special consideration because if their sources are indoors levels can rise over the recommended exposure levels quickly and without notice.

In addition to the outdoor criteria pollutants, indoor pollutants can include carbon dioxide, mold, radon, pesticides, and many others. Volatile organic compounds (VOCs) from cleaning chemicals and byproducts of modern manufacturing processes are sometimes two to five times higher indoors. These pollutants are particularly insidious because they can be continually released by cooking, cleaning, off-gassing from furniture or other building materials, paints, glues, polishes, beauty products, and several other sources to build up in indoor spaces.

Every indoor environment has a unique combination of pollutant sources and exchange with outside air. Modern buildings are typically built very “tight,” which means they allow very little air exchange with the outside. This design is energy-efficient but extra care needs to be taken to ensure that pollutants don’t build up if little outside air is coming in. This is where the sensor suite in Molekule Air Pro steps in.

Molekule Air Pro is an indoor AQI monitor

Molekule Air Pro is equipped with sensors suitable to react to tiny changes in the indoor atmospheric composition. It uses the optical properties of light to detect particles and now, in our latest firmware update, a chemical sensor to measures chemicals in the air by activating carbon dioxide, relative humidity, and VOC monitoring.

The Molekule Air Score

To summarize what is in your air, we have developed a single Air Score that combines VOC and PM readings from the sensor suite in Air Pro. It follows the same basic scheme as the EPA’s AQI but with four levels. 0 to 100 is green and below recommended exposure levels. 101 to 200 is yellow to represent levels that are elevated but really only a concern for sensitive groups. 201 to 300 is red and the range in which most people should consider reducing activity or mitigating the source of pollution. Over 300 is purple and indicates severely bad air quality.

The Molekule air purifier app showing readout for Living Room Molekule Air Pro

The Molekule app showing a living room with an Air Pro and a nice air score

Auto Protect mode relies on the Air Score to increase the fan speed.

Air Pro showing good air quality

Air Pro showing a room with good air quality

When the Air Score rises, Auto Protect mode will automatically increase fan speed to compensate.


Full report of the Molekule Air Score on Molekule mobile app

A full report of the Molekule Air Score

In addition to sensing more components of the atmosphere, Air Pro also provides a more specific measure of the three sizes of PM it detects. Both the app and a device screen will now show the micrograms per cubic meter concentration of each particle size along with the usual severity level from good to very bad.

Air Pro showing PM in micrograms and too much CO2

Air Pro showing PM in micrograms and too much CO2

The chemical sensor

The activated chemical sensor contains elements that reversibly react with specific airborne chemicals to provide a measurement of the atmosphere and adds 3 dimensions to your view of indoor air quality.


TVOC stands for “total volatile organic compounds” and is a representation of any VOC that is in the air. See this blog to learn more about VOCs and their common sources like paints, cleaning products, and building materials, or visit the EPA to see a list of VOCs that have a negative impact on indoor air quality. Not all VOCs are necessarily toxic, for example pouring a glass of wine or applying essential oils will aerosolize VOCs that can be detected by the sensor. However, even some harmless VOCs can react with ambient ozone over time to become more toxic, so it’s a good idea to be aware if there is a consistently high level of VOCs.

VOCs are sometimes continually released from sources in the home. PECO technology can break them down to prevent them from building up indoors, but in homes with continuous sources, Air Pro may always detect some base level of VOCs. If set to Auto Protect, Air Pro will continually increase fan speed until a good or green level is reached.

Molekule app showing the approximate VOC level and Air Score color

The Molekule app showing the approximate VOC level and Air Score color


Carbon dioxide or CO2 is produced by most living things and in significant amounts by animals like humans. Levels of carbon dioxide over 1400 ppm may impact cognitive function, which is a concentration that can be reached by merely not opening the window at a meeting or other gathering. In addition, elevated CO2 levels are often an indicator of poor ventilation, which could mean airborne viruses and bacteria are also accumulating. Air Pro also does not factor CO2 into the Air Score, but does provide the four colored levels to indicate severity. See our blog on stale air to learn more about ventilation solutions.

Molekule app showing the approximate CO2 level and Air Score color

The Molekule app showing the approximate CO2 level and Air Score color


RH is Relative humidity, a gauge of how much moisture is in the air. Ideal relative humidity is between 30% and 60%. Too much can foster mold growth and not enough can dry out your airways which makes them more vulnerable to infection. Air Pro does not factor RH into the Air Score. Instead it will indicate if the air is either too wet or too dry with the four colored levels. See our blog on RH to learn more about how to manage the humidity levels in your home.

Molekule app showing the approximate Relative Humidity and Air Score color

The Molekule app showing the approximate Relative Humidity and Air Score color


How to Upgrade Air Pro

Upgrading to activate the chemical sensor and Air Score is simple. The app that displays the new sensor readings can be downloaded or upgraded as normal according to the operating system of your smartphone. To update the firmware in Air Pro, first be sure it’s connected to wifi, then unplug the device for about 30 seconds, then plug it back in. It should restart once or twice, then it will be ready.

Always keep in mind that there are air pollutants that Air Pro or other air quality monitors are not detecting, and that no air purifier can completely protect you from the effects of air pollution or airborne infectious diseases.


If you have any questions you can always contact, or just give us a call at 1-855-999-9069. We’re available Monday through Sunday 7am to 5pm Pacific Time. Also, keep an eye on our FacebookInstagram, and Twitter accounts for more information on Molekule and what we’re doing about air quality.

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