Indoor air quality can be hard to judge because many pollutants that affect a home are invisible. Smoke can drift indoors from wildfires, cooking can spike particulate levels, poor ventilation can raise carbon dioxide levels, and everyday products such as cleaners, paint, and furniture can release volatile organic compounds.

That is where an indoor air quality monitor can be useful.

We recently tested the Breathe Airmonitor Plus, an 8-in-1 smart indoor air quality monitor from Breathe Tech. What makes this compact device interesting is the number of air-quality measurements it combines into one monitor. It tracks PM1, PM2.5, PM10, carbon dioxide (CO₂), total volatile organic compounds (TVOCs), formaldehyde (HCHO), temperature, and relative humidity in real time.

Our testing timing was particularly useful. We used the Airmonitor Plus in a normal home in the Northeast during periods when smoke from Canadian wildfires affected outdoor air quality, and we continued using it as fall allergy season arrived.

After living with it, we found the Airmonitor Plus an easy way to get much more information about indoor air than many entry-level air monitors provide—and its ability to monitor TVOCs and formaldehyde is one of its most useful differentiators.

What is the Breathe Airmonitor Plus?

What is the Breathe Airmonitor Plus?GearBrain

The Airmonitor Plus is essentially a small environmental sensor station for your home, apartment, office, or classroom.

Instead of giving you only temperature and humidity or measuring just CO₂ and particulate matter, the device continuously monitors eight environmental measurements:

Breathe Tech uses laser-based optical particle counting for particulate matter and a non-dispersive infrared, or NDIR, sensor for CO₂. According to the company, the latter measures actual CO₂ rather than estimating CO₂ from VOC readings, as some lower-cost monitors do.

One important distinction: the Airmonitor Plus does not detect carbon monoxide (CO). CO and CO₂ are different gases, and this product should never replace a certified carbon monoxide alarm.

BREATHE Airmonitor Plus Indoor Air Quality Monitor w/CO₂, PM & App. Gen 2.

List Price: $119.99

Compact design makes it easy to put almost anywhere

Compact design makes it easy to put almost anywhereGearBrain

One of the first things we liked about the Airmonitor Plus was its size.

The monitor measures just 3.3 x 2.8 x 1.7 inches (84 x 70 x 43 mm) and weighs approximately 3.1 ounces (90 grams), according to Breathe Tech's specifications. That makes it easy to put on a desk, nightstand, kitchen counter, shelf or other small surface without having another large smart-home device taking up space.

It also has a built-in 1,600mAh rechargeable battery. Breathe Tech rates battery life at up to six hours depending on settings, and the monitor charges through USB-C using a 5V/2A power source.

We particularly liked having the battery because it makes the Airmonitor Plus portable. You can leave it plugged in for continuous monitoring, then unplug it when you want to check another room.

For example, you could monitor the bedroom overnight, move it into a home office during the workday, and then place it in the living room or kitchen.

Breathe Tech recommends leaving the monitor connected to power for uninterrupted long-term monitoring, while using the battery primarily when moving it around the home.

Testing Airmonitor Plus during wildfire smoke and allergy season

Testing Airmonitor Plus during wildfire smoke and allergy seasonGearBrain

We tested the Airmonitor Plus in a normal home rather than a controlled laboratory environment. That gave us an opportunity to see how useful the information could be under real-world conditions.

Our testing coincided with periods when smoke from Canadian wildfires was affecting parts of the Northeast. We also continued testing as fall allergy season arrived.

That made PM monitoring particularly interesting.

PM2.5 is especially useful for smoke and other fine airborne particles, while PM10 can help identify larger airborne particles associated with dust and pollen. Breathe Tech notes that PM readings can also change because of ordinary household activities such as cooking, burning candles, and cleaning.

Instead of wondering whether the air in a room had changed, we could look at the monitor and see actual measurements.

The display is somewhat small, which isn't surprising given the unit's compact size. However, we could read the numbers without much trouble. We would rather have the compact footprint than a significantly larger monitor just to accommodate a bigger screen.

One feature we particularly liked: formaldehyde and TVOC monitoring

One feature we particularly liked: formaldehyde and TVOC monitoringGearBrain

Airmonitor Plus is the first smart air monitor we have tested that also functions as both a formaldehyde detector and TVOC monitor, and we think this is one of the product's more compelling features.

Why does that matter?

Volatile organic compounds can come from products people use every day, including cleaning products, air fresheners, paint, varnishes, adhesives, furniture, carpets, solvents, cosmetics and perfumes. Formaldehyde can also be emitted by certain composite-wood products, flooring, paints, adhesives, fabrics and building materials.

That makes these sensors useful in situations you may not immediately associate with air pollution.

Consider what happens after a cleaning team deep-cleans your home. The house may look and smell clean, but cleaning chemicals can affect TVOC levels. With Airmonitor Plus, you can watch those readings change and decide whether to open windows or improve ventilation.

The same applies after painting a room, installing new flooring, bringing new furniture into the house or using strong cleaning products.

Instead of relying on whether you can smell something, you have another source of information about how the indoor environment is changing.

The specification sheet notes that the formaldehyde measurement comes from the metal-oxide VOC sensor response, not a separate dedicated formaldehyde sensor. That's an important technical distinction for buyers to understand.

Real-time alerts tell you when something changes

Real-time alerts tell you when something changesGearBrain

You don't have to stare at the screen throughout the day.

The Airmonitor Plus has an audible alarm that can alert you when certain air-quality conditions reach configured thresholds. During our testing, we liked having the monitor call our attention to changes instead of requiring us to repeatedly check the readings.

The system can also guide you on what to do when conditions change.

That is arguably where an air monitor becomes more useful. Numbers by themselves don't mean much to many consumers. Knowing that ventilation may be needed, for example, makes the data more actionable.

Breathe Tech recommends positioning the monitor around breathing height and keeping it away from heating vents, air-conditioning outlets, direct sunlight, and open windows that could distort readings. It also advises against placing it directly next to an air purifier or humidifier unless you are intentionally testing that device's effect.

Breathe Tech app and Wi-Fi connectivity

The Airmonitor Plus connects to a home network using 2.4GHz Wi-Fi. It does not support 5GHz Wi-Fi, so buyers should know that before setup.

The free Breathe Tech mobile app supports iOS 13.0 or later and Android 6.0 or later. Bluetooth is used during initial setup, after which the monitor communicates through Wi-Fi.

We tested the app on an iPhone 14 Pro running an iOS version newer than iOS 13, and the physical monitor and mobile app worked well for how we wanted to use the product.

The app is especially valuable because you aren't limited to whatever is currently displayed on the monitor. You can remotely check readings, receive notifications, and look at historical information.

Breathe Tech currently provides up to 90 days of cloud-based historical data, along with graphs and the ability to export readings as a CSV file. These features require no subscription, which is a nice bonus.

That data-export capability could be especially useful for schools, offices, HVAC professionals or homeowners trying to identify patterns over longer periods.

The monitor can also operate without Wi-Fi. You will still get live measurements on its display, but remote monitoring, notifications, historical cloud data, and exports require a Wi-Fi connection.

BREATHE Airmonitor Plus Indoor Air Quality Monitor w/CO₂, PM & App. Gen 2.

List Price: $119.99

What Airmonitor Plus can—and cannot—do in a smart home

Airmonitor Plus fits nicely into a connected home because it gives you remote visibility into something most smart-home systems don't show particularly well: the air quality around you.

However, consumers need to understand the difference between monitoring air and treating air.

Airmonitor Plus monitors conditions. It doesn't clean your air.

If PM2.5 spikes because wildfire smoke has entered your house, the Airmonitor Plus can tell you about the increase. It cannot remove those particles. Likewise, it can tell you when TVOC readings rise after cleaning, but it cannot filter those chemicals from the room.

You have to take the next step, which could mean increasing ventilation when outdoor conditions permit, identifying and removing the pollution source, adjusting humidity, or operating an appropriate air purifier.

That distinction actually makes the Airmonitor Plus attractive for people who don't want a large smart air purifier in every room. Air purifiers can take up substantial floor space, especially in bedrooms and apartments. A small monitor can instead tell you where and when you may have an air-quality problem so you can decide what action makes sense.

Where can you use Airmonitor Plus?

Although we tested the monitor in a house, we think it could be useful in several places.

Homes and apartments are the obvious choice, particularly bedrooms, nurseries, kitchens, home offices and living rooms. Schools and classrooms could benefit from CO₂ monitoring because rising CO₂ can indicate insufficient ventilation. Offices and conference rooms are another logical application.

The portable design also lets one monitor compare conditions across several rooms, rather than permanently installing a separate sensor everywhere.

For the most consistent historical information, though, we would leave it plugged in and stationary. Moving a monitor from room to room makes long-term trends harder to interpret because the data no longer comes from the same environment.

Airmonitor Plus specifications

Here are the key specifications buyers should know:

• Sensors: PM1, PM2.5, PM10, CO₂, TVOC, formaldehyde, temperature and relative humidity
• CO₂ technology: NDIR
• Particle technology: Laser-based optical particle counting
• TVOC technology: Metal-oxide gas sensor
• CO₂ range: 400–5,000 ppm
• Formaldehyde range: 0.00–1.25 mg/m³
• Operating temperature: 14°F–122°F (-10°C–50°C)
• Operating humidity: Up to 80–85% RH depending on the published specification
• Wi-Fi: 2.4GHz 802.11 b/g/n
• Battery: 1,600mAh, 5.4Wh rechargeable battery
• Battery life: Up to six hours depending on settings
• Power: USB-C, 5V/2A
• Dimensions: 3.3 x 2.8 x 1.7 inches
• Weight: 3.1 ounces
• Mobile support: iOS 13+ and Android 6.0+
• Ingress protection: IPX0
• Certifications: FCC, CE, and ISED

Price and value

Breathe Tech provided a review price of $119.99, which puts the Airmonitor Plus roughly in the middle of the consumer air-monitor market. The company's Amazon page lists the product at $99.99 (17% off), although its online store was showing a $129.99 single-unit price when we checked, so shoppers should confirm the current price before buying.

For comparison, basic monitors such as SwitchBot's CO₂-focused indoor monitor can be found around $60, while premium products such as Airthings View Plus can cost more than $300 and add measurements such as radon.

The important question, therefore, isn't whether Airmonitor Plus is the least expensive monitor. It isn't.

Its value comes from how much it measures in one compact product—particularly the combination of three particulate sizes, actual NDIR CO₂ monitoring, TVOCs, and formaldehyde.

Breathe Tech also provides a two-year warranty, a 30-day return period, and no required subscription for its app features.

BREATHE Airmonitor Plus Indoor Air Quality Monitor w/CO₂, PM & App. Gen 2.

List Price: $119.99

What we liked

An alert on Amazfit T Rex 3 smartwatch from Breathe Airmonitor PlusGearBrain

The strongest feature is the breadth of the monitoring. Getting eight measurements from such a small device gives homeowners considerably more insight than a basic CO₂ or PM2.5 monitor.

We also liked the compact size, rechargeable battery, USB-C power, remote monitoring, and in-app historical data. The audible warning is useful because you don't have to constantly watch the display, and the TVOC/formaldehyde capabilities are particularly interesting for people concerned about cleaning products, new furniture, renovations, or other indoor chemical sources.

Another unexpected benefit showed up during our testing. I was wearing an Amazfit T-Rex 3 smartwatch, connected to my iPhone via Bluetooth. When the Breathe Tech app sent an air-quality notification to my smartphone, it also mirrored that notification on my Amazfit watch. The first time an Airmonitor Plus alert appeared on my wrist, I was a little surprised, but I quickly came to appreciate it.

This doesn't mean the Airmonitor Plus directly integrates with the Amazfit T-Rex 3. Instead, the smartwatch displayed notifications received by the connected smartphone. Still, it's a useful real-world feature because I didn't need my phone in my hand—or even to look at the Airmonitor Plus—to know an air-quality condition needed my attention. It also shows that these alerts aren't necessarily limited to Apple Watch users. If your smartwatch can display notifications from your smartphone, Breathe Tech Airmonitor Plus alerts may be able to appear on your wrist as well, depending on your phone, watch, and notification settings.

Our wildfire-smoke and allergy-season testing also demonstrated why monitoring multiple particle sizes can be useful instead of relying on temperature, humidity, or CO₂ alone.

What we'd like to see improved

Small screen sizeGearBrain

Our biggest hardware complaint is simply the small screen. The readings were legible during our testing, but consumers who want to glance at their air-quality data from across a room may prefer a monitor with a larger display.

We would also like to see broader smart-home integration in products like this. The real potential for air-quality monitoring comes when sensor data can trigger other connected devices automatically—for example, having compatible HVAC equipment, ventilation systems, or air purifiers respond when specific conditions change.

And remember that the Airmonitor Plus isn't a replacement for smoke or carbon monoxide alarms and doesn't actually clean the air.

Who should buy the Breathe Airmonitor Plus?

The Airmonitor Plus makes the most sense for consumers who want to understand why the air inside their home is changing, rather than seeing only a generic air-quality score.

It is particularly compelling for households concerned about wildfire smoke, seasonal allergens, ventilation, cooking particles, cleaning chemicals, renovations, new furniture, or humidity. We can also see it being useful in schools, offices, nurseries, and apartments where space is limited.

If you only want temperature, humidity, and CO₂ readings, you can spend less. Likewise, consumers specifically concerned about radon will need a monitor designed to detect it.

But if you want one compact device that can monitor CO₂, three sizes of particulate matter, TVOCs, formaldehyde, temperature, and humidity, the Airmonitor Plus covers an unusually broad range of indoor-air conditions.

GearBrain verdict

After testing the Breathe Airmonitor Plus in a real home during challenging outdoor air conditions and allergy season, we came away impressed by how much sensing Breathe Tech has packed into such a small device.

The TVOC and formaldehyde monitoring stood out most because these measurements give homeowners visibility into pollutants they may otherwise overlook. Combine that with PM1, PM2.5, PM10, and CO₂ monitoring, and the device provides a more complete picture of what's happening inside a room than many inexpensive air monitors.

The small screen is a compromise, and buyers should understand that this is a monitoring device—not an air purifier or life-safety detector. But its portability, eight measurements, app connectivity, alerts, and reasonable price make the Airmonitor Plus a useful addition for consumers who want to better understand the air they're breathing without putting a bulky air purifier in every room.

Pros: Eight air-quality measurements; NDIR CO₂ sensor; TVOC and formaldehyde monitoring; compact and portable; rechargeable battery; Wi-Fi/app access; historical data and CSV export; no subscription.

Cons: Small display; 2.4GHz Wi-Fi only; battery is better suited to portable checks than all-day cordless operation; doesn't detect carbon monoxide or radon; monitors air but does not clean it.

Price: $119.99 review/list price supplied by Breathe Tech; current retail pricing may vary.

Best for: Homeowners, apartment dwellers, parents, schools, offices, and smart-home users who want a compact way to monitor multiple indoor air-quality factors.

Check out The GearBrain, our smart home compatibility find engine, to find the smart air purifiers compatible with your existing smart products or ones that work with Google Assistant and Amazon Alexa-enabled devices.

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