Best Air Quality Monitors, What to Measure and Why (2026)
Measure first, buy second. A $100 air quality monitor tells you exactly what is wrong with your air, so you spend money on the right fix instead of guessing.
Last updated: April 2026 · By the CleanAirHomeLab team
Why You Need a Monitor Before a Purifier
Most people buy an air purifier because they sneeze, smell something, or read a scary headline about air pollution. Then they pick whatever has good Amazon reviews and hope for the best.
That is backwards. An air quality monitor costs $99-299 and tells you exactly what is in your air. Maybe your PM2.5 is fine but your CO2 is through the roof, the fix is opening a window, not buying a $500 purifier. Maybe your radon is at 8 pCi/L, no purifier fixes that; you need a radon mitigation system.
The monitor pays for itself by preventing a wrong purchase. And once you do buy a purifier, the monitor proves whether it is actually working.
The Smart Order
Buy an air quality monitor and run it for 2 weeks
Look at the data, what is actually elevated?
If PM2.5 is high, buy a HEPA purifier sized for your room
If CO2 is high, improve ventilation (open windows, add exhaust fans)
If radon is above 4 pCi/L, hire a radon mitigation company
If VOCs are high, find the source (new furniture, paint, cleaners) and ventilate
What to Measure
Six readings matter for home air quality. Not every monitor tracks all six. Here is what each one tells you and why it matters.
Monitor Reviews
#1
Airthings Wave Plus
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Six sensors in one device: radon, CO2, VOCs, humidity, temperature, and air pressure. Battery-powered. Mounts on any wall.
Key Specs
Sensors
Radon, CO2 (NDIR (non-dispersive infra-red)), TVOCs, Humidity, Temperature, Air Pressure
Radon Range
0-500+ pCi/L
CO2 Range
400-5,000 ppm
VOC Range
0-10,000 ppb
Power
2x AA batteries (lasts ~16 months)
Connectivity
Bluetooth (requires Airthings app or Hub for WiFi)
Display
None (wave-to-read LED: green/yellow/red)
Dimensions
4.7 inches diameter, 1.4 inches deep
Warranty
1 year
What We Like
Only consumer monitor that tracks radon AND CO2 AND VOCs in one device
Battery powered (2x AA) — no wires, mount anywhere including basements
Wave your hand in front to get a color-coded reading (green/yellow/red)
Free Airthings app with long-term trends and history
Radon readings are EPA-accepted for home use (not mitigation certification)
What Could Be Better
No PM2.5 sensor — cannot track particle pollution
Radon takes 7+ days to show an accurate reading (radon measurement is slow by nature)
Bluetooth range is limited — must be within 10 feet to sync with phone
No display screen — you need the app or wave gesture for readings
Bluetooth-only without the separate Airthings Hub, so no continuous cloud logging on its own
Our Verdict
The Airthings Wave Plus is the best starting point if you have never tested your home air. It covers the six most important readings and runs on AA batteries, so you can put it anywhere. The big miss is no PM2.5 sensor. If you care about particle pollution (allergies, wildfire smoke), pair it with the View Plus or a dedicated PM2.5 monitor, so you know whether the cough that started in October is from poor air quality or something else.
#2
Airthings View Plus
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The most complete home air monitor. PM2.5 + radon + CO2 + VOCs + humidity + temperature + air pressure. Built-in WiFi and e-ink display.
Key Specs
Sensors
PM2.5, Radon, CO2 (NDIR (non-dispersive infra-red)), TVOCs, Humidity, Temperature, Air Pressure
PM2.5 Range
0-1,000 ug/m3
Radon Range
0-500+ pCi/L
CO2 Range
400-5,000 ppm
Power
6x AA batteries or USB-C
Connectivity
Wi-Fi 2.4 GHz, Airthings SmartLink, Bluetooth LE
Display
2.9 in e-paper (always on, low power)
Dimensions
3.2 x 3.2 x 1.4 inches
Warranty
1 year
What We Like
Adds PM2.5 sensor to everything the Wave Plus tracks — the full picture
E-ink display shows current readings without needing a phone
Built-in WiFi — sends data to cloud automatically, no hub needed
IFTTT and SmartThings integration for automation triggers
Battery powered with optional USB-C — still mounts anywhere
What Could Be Better
At $299, it is the most expensive consumer monitor on this list
PM2.5 sensor is less accurate than dedicated PM monitors like PurpleAir
E-ink display is small and hard to read from across the room
Radon measurement is the same slow process — still takes a week for accuracy
Cloud-dependent — if Airthings servers go down, you lose real-time data
Our Verdict
The Airthings View Plus is the only monitor that tracks everything: radon, PM2.5, CO2, VOCs, humidity, temp, and air pressure. If you only want to buy one device, this is it. The PM2.5 sensor is good enough for general awareness, but if you are in a wildfire zone and need precise particle tracking, pair it with a PurpleAir or AirGradient for PM2.5 accuracy.
#3
AirGradient ONE
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Open-source air quality monitor. Tracks PM2.5, CO2, and TVOCs. Data stays local if you want — no cloud dependency. Loved by the tinkerer crowd.
Key Specs
Sensors
PM2.5 (Plantower PMS5003), CO2 (SenseAir S8/S88 NDIR), TVOC and NOx (Sensirion SGP41), temperature and humidity (Sensirion SHT40)
PM2.5 Accuracy
+/-4 ug/m3 from 0-100 ug/m3, +/-8% from 100-500 ug/m3
CO2 Range
0-10,000 ppm, auto-calibrated every 7 days
Power
USB-C, 5V at 2A or more (no battery)
Connectivity
WiFi 2.4 GHz (802.11 b/g/n)
Display
1.3 inch OLED (128x64) plus 11 RGB LEDs
Firmware
Fully open source, CC-BY-SA 4.0 (schematics and 3D files too)
Model
I-9PSL (9th generation)
Warranty
12 months
What We Like
Open-source firmware — full control over your data and device
True NDIR CO2 sensor (Sensirion SCD41) — not an estimate like Airthings
PM2.5 sensor (Plantower PMS5003T) is well-regarded for accuracy
Can run entirely local with Home Assistant — no cloud needed
At $180, it is the best value for PM2.5 + CO2 accuracy
What Could Be Better
No radon sensor — you still need an Airthings or test kit for radon
Requires USB-C power — no battery option, must be plugged in
Setup is more technical than Airthings (firmware updates, WiFi config)
The OLED display is small — not easy to read across the room
Less polished build quality than Airthings — functional, not pretty
Our Verdict
The AirGradient ONE is the best air quality monitor for accuracy per dollar. Like the Airthings units it uses a true NDIR CO2 sensor, so the difference is openness rather than sensor class: if you use Home Assistant or want local data control, there is nothing better. The tradeoff: no radon, no battery, and you need to be comfortable with some basic setup. Pair it with an Airthings Wave Plus for radon, and you have better coverage than any single device.
#4
Temtop M10i
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Budget PM2.5 monitor with WiFi and app. Does one thing — tracks particles — and does it well for the price.
2200 mAh rechargeable battery, about 6 hours per charge, DC 5V
Connectivity
WiFi
Dimensions
82 x 82 x 31 mm (3.2 x 3.2 x 1.2 in), 200 g
Warranty
1 year
What We Like
At $99, cheapest WiFi-connected PM2.5 monitor worth buying
Clear LCD display shows PM2.5, AQI, temperature, and humidity
Temtop app tracks historical data with graphs
Rechargeable battery lasts several hours — portable for spot checking
Small and lightweight — easy to move between rooms
What Could Be Better
PM2.5 only — no CO2, no VOCs, no radon
Laser particle sensor is less accurate than Plantower sensors in AirGradient
WiFi connectivity can be unreliable (2.4 GHz only, setup can be fussy)
App is basic and sometimes slow to sync
No smart home integration — no Alexa, no Home Assistant
Our Verdict
The Temtop M10i is the right buy if you just need to know your PM2.5 levels and nothing else. It is a solid budget entry point. Use it to check if your purifier is actually working, or to see how outdoor pollution affects your indoor air. But if you want CO2, VOC, or radon data, spend more on an AirGradient or Airthings.
#5
PurpleAir Flex
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Dual laser PM2.5 sensor for indoor or outdoor use. Feeds the PurpleAir community map — the most trusted real-time air quality network.
Key Specs
Sensors
Dual Plantower PMS6003 laser counters (PM1.0, PM2.5, PM10) plus a BME environmental module for temperature, humidity and pressure
Intended Use
Outdoor. PurpleAir sells the Flex as an outdoor PM2.5 monitor.
PM2.5 Range
0-1,000+ ug/m3
Power
USB-C (5V, no battery)
Connectivity
WiFi (2.4 GHz)
Display
None (app + web dashboard + PurpleAir map)
Weather Resistance
IP67 rated (indoor/outdoor)
Dimensions
3.9 x 3.3 x 2.4 inches
Warranty
1 year
What We Like
Dual Plantower laser sensors provide cross-checked PM2.5 readings — more accurate than single-sensor monitors
Contributes to PurpleAir real-time map — your data helps your whole neighborhood
Works indoors or outdoors (weather-resistant design)
No subscription fees — data is free on the PurpleAir map forever
API access for custom dashboards and Home Assistant integration
What Could Be Better
No CO2 and no radon; PurpleAir positions the Flex as an OUTDOOR monitor
Must be plugged in via USB-C — no battery
No built-in display — readings are on the app or PurpleAir website
WiFi setup can be tricky (2.4 GHz only, WPA2 required)
Raw readings read high compared to EPA reference monitors — apply correction factor
Our Verdict
The PurpleAir Flex is the gold standard for PM2.5 monitoring. Its dual sensors give you confidence in the readings, and the community map shows real-time air quality for your exact location. If you live in a wildfire-prone area, this plus a basic Airthings for radon gives you better data than any single all-in-one monitor, so you know exactly when outdoor smoke crosses your indoor threshold and it is time to close windows and run the purifier. Raw PurpleAir readings run high. Apply the EPA correction factor for accuracy.
Airthings vs AirGradient: Which One?
These two brands take different approaches. Airthings builds polished consumer devices with radon sensors and battery power. AirGradient builds accurate, open-source monitors that integrate with smart home systems. Here is how they compare:
Choose Airthings If...
You need radon monitoring (only Airthings has it in consumer devices)
You want battery power, no wires, mount in the basement or closet
You prefer a simple setup with a phone app, plug and play
You want one device that covers everything (View Plus)
Choose AirGradient If...
You want the most accurate CO2 readings (true NDIR sensor)
You use Home Assistant or want full local data control
You like open-source hardware and want to customize firmware
Budget matters, $180 vs $229-299 for Airthings
Our recommendation: If you can afford both, get an AirGradient ONE for PM2.5 and CO2 accuracy, plus an Airthings Wave Plus for radon. Total: $409 for the most complete home air monitoring setup you can build. If you can only pick one, the Airthings View Plus at $299 covers the most ground.
Feature Comparison
Feature
Wave Plus
View Plus
AirGradient
Temtop
PurpleAir
PM2.5
No
Yes
Yes
Yes
Yes
CO2
Estimated
Estimated
True NDIR
No
No
VOCs
Yes
Yes
Yes
No
No
Radon
Yes
Yes
No
No
No
Display
LED only
E-ink
Small OLED
3.5" LCD
None
Battery
Yes (AA)
Yes (AA)
No
Yes
No
WiFi
Needs Hub
Built-in
Built-in
Built-in
Built-in
Open Source
No
No
Yes
No
API only
Price
$229
$299
$180
$99
$199
What the Numbers Mean
Your monitor gives you numbers. But what counts as good, bad, or dangerous? Here is a quick reference based on EPA guidelines and WHO recommendations.
Reading
Good
Moderate
Unhealthy
Dangerous
PM2.5
0-12 ug/m3
12-35 ug/m3
35-55 ug/m3
55+ ug/m3
CO2
400-800 ppm
800-1,000 ppm
1,000-2,000 ppm
2,000+ ppm
VOCs (TVOC)
0-220 ppb
220-660 ppb
660-2,200 ppb
2,200+ ppb
Radon
0-2 pCi/L
2-4 pCi/L
4-8 pCi/L
8+ pCi/L
Humidity
40-50%
30-40% or 50-60%
<30% or >60%
<20% or >70%
PM2.5 ranges follow the US EPA AQI breakpoints. Radon follows the EPA action level of 4 pCi/L. CO2 ranges are based on ASHRAE ventilation standards.
Common Questions
Do I need an air quality monitor if I have an air purifier?
Yes. A monitor tells you if your purifier is actually working. Many people run purifiers on auto mode and assume the air is clean. A PM2.5 monitor shows you the real number. You might find that your purifier's auto mode is not aggressive enough, or that your kitchen cooking spikes PM2.5 higher than you thought.
Should I buy an all-in-one monitor or separate sensors?
All-in-one monitors like the Airthings View Plus are the easiest option. But separate sensors often give more accurate readings. The best setup for serious monitoring: an AirGradient ONE for PM2.5 and CO2 (most accurate sensors), plus an Airthings Wave Plus for radon. Two devices, every sensor covered, better accuracy than any single unit.
How accurate are consumer air quality monitors?
PM2.5 sensors in consumer monitors are typically within 10-20% of EPA reference monitors in normal conditions. They get less accurate at very low or very high readings. CO2 sensors vary more: true NDIR sensors (like in the AirGradient) are accurate to about 30 ppm. Estimated CO2 sensors (like in Airthings) are less precise. Radon sensors need at least 7 days to give a reliable reading.
Where should I place an air quality monitor?
At breathing height (3-5 feet off the floor) in the room where you spend the most time. Keep it at least 3 feet away from windows, doors, vents, and cooking areas, these create temporary spikes that do not represent your average air quality. For radon, place the monitor in the lowest lived-in level of your home (often the basement).
How is CO2 actually measured, and does the sensor type matter?
NDIR (non-dispersive infra-red) sensors measure CO2 directly by shining infra-red light through the air, and are the type used in every monitor we recommend here. Airthings specifies NDIR on both the Wave Plus and the View Plus, over a 400 to 5,000 ppm range, as does the AirGradient ONE. Some cheaper devices instead infer a CO2-equivalent figure from a VOC sensor; those are fine for a high/medium/low sense of ventilation but should not be read as exact ppm. Correction, September 2026: this page previously described Airthings CO2 as estimated. That was wrong.
Ready to Clean Your Air?
Once you know what is in your air, the next step is picking the right purifier. We size every pick by CADR and include real filter costs.
Affiliate Disclosure: Some links on this page are affiliate links and may earn us a commission at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. Airthings and AirGradient are direct partners. All others are Amazon Associates links. Full disclosure.
Sources and last review
Specifications on this page are taken from the documents below, on the dates shown. We do not physically test products; read our methodology. Page last reviewed .
Correction, September 2026: this page previously described Airthings CO2 as an estimate derived from VOC readings. Airthings specifies an NDIR sensor on both the Wave Plus and the View Plus.
