What Is Indoor Air Quality Monitoring?


We take in 20,000 breaths every single day and spend 90% of our time indoors, so the monitoring of the quality of the air we breathe matters.

Indoor air quality monitoring is a continuous process of reading commonly found pollutants in the indoor air in order to improve health and comfort. Nowadays, this is achieved by using tools that are equipped with sensitive sensors, which are referred to as air quality monitors.

While in the past, it was common to mail out samples and wait on a laboratory for the results, homeowners now have more control with personal air quality monitors. These sophisticated tools are becoming more popular, but not all are created equally.

In this post, we’ll talk about what some of the commonly found pollutants are in the indoor air, as well as how to pick the air quality monitor that’s right for you and your home.


Pollutants that Indoor Air Quality Monitors Should Identify

Air quality monitors typically will give readings of several pollutants, but not all. Before you can decide just what tools you need to help you monitor the air in your home, you must first know what the pollutants to monitor are.


Volatile Organic Compounds (VOCs)

Most monitors measure volatile organic compounds, or VOCs, first and foremost. VOCs are gases in the air that are known to create smog outdoors, but they’re important for indoor settings as well. As a matter of fact, some VOCs exist at higher levels inside than outside! VOCs are found in cleaning supplies, particle board furniture, laminate flooring, insulation, adhesives, paints, and other things.


Carbon Dioxide and Carbon Monoxide

Carbon dioxide and carbon monoxide are also commonly found. Carbon dioxide is mostly harmless, but when the amount of oxygen is constricted, carbon monoxide forms instead. Carbon monoxide is quite poisonous, but its presence is nearly undetectable without some sort of sensor. For this reason, you probably already have a basic carbon monoxide monitor to help you monitor this pollutant.

Although not as dangerous as carbon monoxide, high carbon dioxide levels can be bad, too. The presence of carbon dioxide indicates the lack of ventilation and fresh air. Without enough oxygen, our brain function can be greatly affected. We may feel fatigued, disoriented, or lack concentration.



Radon is another pollutant to monitor. It typically comes from the soil and seeps into the home from the foundation. Sadly, most homeowners rarely test their home for radon, even though every year reports keep coming out that homes have higher radon levels than previously reported. Radon monitoring is still in the “mail the sample out” stage, although there are some portable units that have recently entered the mainstream consumer market.


Fine Particles (PM2.5)

Fine particles (often labeled as PM2.5) are especially important since the average air filters can’t filter them out. These particles are less than 2.5 micrometers across. Because of their small size, it’s easy for them to enter the body and make their way to the bloodstream. Fine particles aren’t necessarily one particular thing since they’re just defined by their small size. They could be dust, dirt, gases, VOCs, smoke, and anything else that’s small and affects our health and comfort.

It’s worth noting that HEPA air filters can filter fine particles out, but it’s still good practice to try to completely eliminate these particles. HEPA filters just trap those particles, but they will still exist in your home until your throw out the filter. Also, if the particles are microbial, they may be replicating faster than you’re replacing the HEPA filters.



Mold spores are another issue and tend to grow on organic matter that’s in dark, damp places. If you have a basement, you’re more prone to mold. Mold is interrelated with humidity. Any room with a relative humidity above 60% will have a hard time keeping mold out. A general air quality monitor won’t be able to detect mold directly, but it will help you monitor the humidity levels.


Why Indoor Air Quality Matters

We spend 90% of our time indoors, and the EPA tells us that indoor air can be 5 times more polluted than the air outside. Homes are built more airtight than ever, trapping those pollutants so that they continuously circulate inside the home. As time goes by, more and more organic matter is formed, making the air even worse and allowing mold to form.


Respiratory Problems

Perhaps the most evident outcome of this change in indoor air quality is the fact that more children now have asthma than ever. Asthma was once a rare occurrence, but not anymore. The rate of asthma in children has almost tripled since the 1980s. Although research is needed to find the correlation, coincidentally asthma in children began to slowly decline once manufacturers were pushed to produce safer products with fewer VOCs and other chemicals.


The Danger of Cancer

Many chemicals are Group 1 carcinogens, meaning that they’re likely to cause cancer. For example, formaldehyde is a commonly found VOC that can off-gas in your home for years and years. It’s found in pressed wood products, paints, and insulation. You could be surrounded by formaldehyde on all four sides in your home literally since it can be found in laminate flooring, furniture, wall paint, wall insulation, and ceiling tiles!

Think back to the news coverage of the trailers that FEMA provided to Hurricane Katrina victims. Formaldehyde was the major cause of why those people became sick and even developed cancer in the years to follow. The US government ultimately had to pay $43 million in a lawsuit settlement.

VOCs aren’t the only cancer-causing chemicals that may be lurking in your home. Radon is another dangerous pollutant that many people have in their homes without even knowing it. It alone kills 21,000 people a year in the United States from lung cancer.


Neurological Problems

The VOCs that give off a sweet smell in your home can cause permanent damage of the central nervous system when inhaled at high concentrations. Some people have experienced changes in brain chemistry and even paralysis after exposure.

What most people don’t realize is that this level of exposure VOCs doesn’t necessarily need to be caused by a sudden incident. The same high concentration of VOCs can be accumulated by the body when exposed over long periods of time.


How to Pick the Best Air Quality Monitor That’s Right for You

First, you’ll need to understand that a single air quality monitor won’t be able to monitor everything. You may need to combine several tools and tests to be able to monitor all the important pollutants. You’ll also need to decide how the air quality monitor will fit in with the rest of your home. Some are simple, handheld tools, while others can work with your entire smart home network by controlling your thermostat, smart assistant service, smartphone, or air purifier.

Just know that the more features an air quality monitor has, the more expensive it is.

It’s wise to use common sense when choosing what’s right for you. Not all homes need to be monitored for everything continuously. You can still use “mail in tests” for some of the pollutants and only upgrade to a more expensive monitor if you realize that there is an issue. Let’s talk about some features that air quality monitors may have and whether you may need them or not.


Total Volatile Organic Compounds (TVOC) Monitoring

A good air quality monitor should be able to monitor VOCs, first and foremost. In a broad study in the 1990s, the EPA has identified over 200 VOCs inside homes, with 48 of those VOCs having significant concentrations that might be a concern for health.

Unfortunately, it isn’t realistic to expect a personal air quality monitor to measure that many VOCs, while being affordable at the same time. For that reason, manufacturers have singled out a smaller number of VOCs that are most relevant to measure for most homes. This measurement is given as a single number called the TVOC. The manufacturer should be able to tell you which particular VOC their monitors use for the primary reading.

Some air quality monitors also give a separate reading for formaldehyde, which is shown as HCHO on the screen display. Given just how many things inside a home off-gas formaldehyde, it’s always a nice bonus to have this separate reading available.

On the other hand, if the air quality monitor is only giving a reading for formaldehyde, you may be missing important information for the other VOCs.

Also, check the range that the air quality monitor has, in case you have a large home. VOCs are heavy and don’t spread as easily as some gases do, so an air quality monitor that’s sitting on your kitchen island may not be able to detect the VOCs in a baby’s nursery if the room is on the other side of the house.


IFTTT and Smart Integration

This is where it gets fun, but if you get swayed by too many cool features, you’ll notice your wallet tends to shrink. In other words, air quality monitors that offer IFTTT and smart integration are more expensive than the simpler ones.

Just how far advanced are air quality monitor nowadays and what’s this thing called IFTTT?

IFTTT is an acronym for “If This, Then That” technology. It’s a way for two devices to communicate by a switch that serves as an intermediary. It can also do other things like simplifying your real and social life through apps, but that’s beyond the scope of this post.

If I push a button on my phone when I leave for work, then my thermostat at home needs to go down two degrees so that my home is cool enough by the time I arrive. And while I’m already pushing buttons, I want my porch lights to turn on so I’m safe when I pull into the garage. And speaking of the garage, the moment my tires hit the driveway, the garage door should be lifted.

That kind of thing.

Some air quality monitors can blend into the rest of your smart home network, and some can work with personal assistant systems like Alexa and Google Assistant devices. Some can automatically communicate with a thermostat like Nest to adjust the HVAC in your home if they detect an unusual reading. At the same time, this can bring energy costs down and reduce your carbon footprint since your HVAC doesn’t need to run as frequently when your’re away at work and the air quality in your home is healthy.

The possibilities don’t stop at thermostat control, though. Some air quality monitors can turn on a dehumidifier if the air gets too moist, and yet again some others can turn on an air purifier if VOC levels shoot up.

The industry is still in its early stages, but there are some manufacturers that are paving the way. Let’s take a look at a few examples of what’s currently available:

  • Air Visual Pro connects to your thermostat to control how your HVAC runs based on the quality of the air.
  • If you’d like an air quality monitor that can connect to Alexa, Google Assistant, Nest, and has IFTTT features, consider the Awair. I personally think the money could be better spent on adding a good formaldehyde monitor rather than the wooden box design and bright display, but the smart home integration of the product is one of the best in the industry.
  • The UHOO is on the pricier end compared to the others, but that’s because it’s able to read twice as many things as its competitors (more on that later). As of writing this post, UHOO is considered to be the most connected air quality monitor. It can even turn on your Roomba vacuum cleaner if you’d like.
  • If you use your ioS devices already through the Eve array of smart home tools, you may wish to add the Eve air quality monitor to your already existing smart network.

Don’t forget that while your air quality monitor is smart, it requires everything it’s connected to be smart as well. You won’t be able to buy just any air purifier if you want the smart connection. You’d obviously need a smart air purifier as well. While this is a great feature, it may not be in your budget, and that’s perfectly ok!

The Awair Glow lets you control a regular air purifier just as well, as long as both devices are plugged into the same outlet. The Awair Glow can still communicate with some other devices like Alexa, for example.


WiFi Connection

With today’s technology, there’s no reason why your air quality monitor would still need Bluetooth, or even a cable to work. It’s almost laughable that so many manufacturers nowadays even list this as a feature.


PM2.5 Monitoring

Fine particulate matter is very important to monitor. Since you’ll be paying a few hundred dollars for an air quality monitor, this feature is a must in my opinion. It’s especially valuable if you intend to upgrade the air filters in your home to HEPA filters. That way, you’ll be able to get a baseline for the particles in the air before you implement the change.

It’s also important to monitor these small particles if you have people with asthma or allergies living in your home, as well as those who may be more sensitive to the air (like pregnant women, the elderly, those with a compromised immune system, babies, small children, cats, and dogs).

Historic Readings

If the device isn’t providing you with data over a long period of time, or datalogging, it will be hard to keep up with it. We all lead busy lives, and an air quality monitor that doesn’t help us assess how the air quality in our homes changes over time is a major negative for me.

In my opinion, the price of air quality monitors that don’t have this functionality needs to be justifiably discounted compared to the monitors that have this feature. Don’t get me wrong, we all have our budgets. Just know that tracking of data is a valuable feature of air quality monitors that might be worth it.



Not all air quality monitors are created equally, and accuracy is one of the areas where you might come across major differences. It isn’t unusual for some air quality monitors to be only accurate within + 20%. Before you buy your next air quality monitor, make sure to find the product specifications or manual. It should tell you just how accurate the device is.

It’s also important to understand what the device measures directly, and what it infers from the direct measurements. I hate to say it, but some manufacturers are notorious for using this argument as a way to excuse away extreme swings in measurements (which are clearly inaccurate). This mostly has to do with carbon dioxide and carbon monoxide readings being derived from VOC readings.

Again, I emphasize that some air quality monitors cannot do everything, especially once you realize that in professional settings all the tools to measure air quality can add up to tens of thousands of dollars. Why not focus on a good monitor that can read VOC levels, and supplement it with other monitors that have already been shown to be more accurate?

For example, the AZ-0004 has consistently proven to be accurate throughout the years when it comes to carbon dioxide readings.

You also need to pay attention to carbon monoxide. Did you know that some industry standards don’t let carbon monoxide alarms to go off at low levels to avoid “nuisance” alarms from going off?

The problem with that is that carbon monoxide exposure is based not only on the amount of carbon monoxide present but also the time of exposure. You may be exposed to low levels of carbon monoxide for long periods of time, but still be at risk. And your carbon monoxide detector may not even be going off to tell you this.

Knowing the exact levels of carbon monoxide can put you in greater control to take preventative measures. Or would you rather be woken up in the middle of the night when carbon monoxide has already been building up for hours, having to save your entire family when you only have 15 minutes left before the damage becomes permanent?

Two final points I wanted to make about carbon monoxide and carbon dioxide –

The build-up of carbon monoxide could be an be an outcome of malfunctioning appliances and the build-up of carbon dioxide could be because the HVAC isn’t ventilating the home properly. Being able to read these two gases in your home could help you identify needed repairs before they become too costly or require emergency service.

Also, an air quality monitor is not a reason to take down the carbon monoxide monitor in your home. Many air quality monitors derive their carbon monoxide and carbon dioxide measurements from other readings, which have notoriously been reported to be inaccurate sometimes as I already mentioned. It’s a good thing to have numbers to go by, but don’t throw out your carbon monoxide monitor yet. This gas is too dangerous to play with.


Comparison to Outdoor Air Quality and Forecasting Based on Weather Predictions

Some air quality monitors have a portable aspect to them, meaning that you can take them outside with you. If you live in a highly polluted area, it might be a good bonus to have a small device to carry along with you. If you have asthma, allergies, or sensitive children or pets, this is definitely something that might be of value. However, for the rest of us, this added feature may not be as necessary.

Other monitors take it upon themselves to run weather reports to predict the quality of the air inside and outside. I see little value in this, at least where I live. If the monitor is already warning and adjusting other smart devices in real time, it’s already doing what it needs to do.


Temperature and Relative Humidity Monitoring

Temperature and relative humidity typically go together. Rarely will you see an air quality monitor that gives a relative humidity reading, but no temperature. If you can have this feature, it’s definitely a major bonus. While an air quality monitor won’t be able to tell you if there is any mold in your home, it can tell you if humidity is high.

Mold growth is severely restricted at humidity levels below 50% (30% to 40% is ideal). If you can maintain this level of humidity in your home, it could potentially save you from a major mold disaster in the future. On the other side of the spectrum, an air quality monitor can make you aware of dry air that’s typical in the winter season. By alarming you of dry air, you may be able to fare better during the cold and flu season.

If you have a dehumidifier, it will most likely already have a relative humidity reading on it. This may make a humidity reading on an air quality redundant. But keep in mind that most portable dehumidifiers can only work in small- to medium-sized rooms, and many of them have a tendency to break down after a year or two if their motor if overworked.  An air quality monitor may be a better solution that can help you continue monitoring the humidity in your home over the long term.


Additional Readings Like Radon, Asbestos, Nitrogen Dioxide and Ozone

The EPA recommends each home be tested for radon every year, but I suspect that this might change in the near future based on new research that’s constantly coming out. More and more homes are being reported as having higher radon levels than previously thought.

Also, the notion that one single sample is enough for one home, or that you can base the radon levels in your home on location and geography alone is slowly disappearing. Radon levels are now being shown to be a function of the way a home was built. If the builder did a poor job creating a poor barrier to block radon from entering from the soil below, the radon levels in your home could be much higher than your neighbors.  Radon levels also constantly fluctuate, so sending one sample off to a lab once in a year may not be representative of what’s really going on in your home.

Although most homes can be affected by radon, homes with basements are at greater risk since they’re deeper in the ground. Short of calling a professional who has the proper equipment to measure and remediate radon, your best (and least expensive) solution may be to start by testing the radon levels yourself first.

If you still insist on a traditional radon test kit, it might be wise to test several areas of your home and test at different times. You may wish to test with the HVAC on or off, as well as how opening or closing the interior doors affects the reading. Keep the windows and exterior doors closed, though.

When it comes to asbestos, hopefully, it isn’t an issue in your home. Most homes nowadays are built without any asbestos. If your home has been built prior to 1970, if your home hasn’t been checked for asbestos, it’s a long overdue test that must be done as soon as possible.

One particular air quality monitor (the UHOO as mentioned before) stood out to me from the crowd because it’s able to read nitrogen dioxide and ozone, so I’d like to end this post discussing those two chemicals. Both are talked about primarily in the context of overall outdoor air pollution. Instead of being related to indoor air quality (IAQ), they’re being talked about in the context of the air quality index (AQI) that’s pertaining to the air outside.

But that doesn’t make these readings unimportant.

The good news is that when these chemicals are found inside a home, the fix is rather easy. If you have a device that emits ions into the air (like an ozone air purifier), simply removing it and allowing for natural ventilation should solve the problem.

Nitrogen dioxide is formed by faulty or poorly vented appliances and kerosene heater., If your air quality monitor is displaying high levels of carbon dioxide, then simply replace or fix those appliances. Although, I must say that nitrogen dioxide also comes from tobacco smoke, so that problem may be a bit more difficult to fix if someone in your home smokes.

Next, learn how to pick the right indoor air quality monitor for your home.