A 60 DOLLARS DIY MONITOR SHOWS WHY YOU'RE TIRED AT HOME — CO2 DOESN'T LIE
A soldered air quality monitor that shows why you wake up tired — bedrooms hit 4,000 ppm CO2 overnight with the windows shut.
by AirGradient
HomeHealth
- difficulty
- ●●○○○
- time
- an evening
- license
- GPL-3.0
- repo
- repo ACTIVE367 stars
●●○○○ · an evening · GPL-3.0 · 367 stars · repo ACTIVE
WHAT YOU’LL NEED
- Electronic parts — full list with part numbers in the repo BOM
- Dev board / microcontroller — runs the project firmware
Partner
COMPAREE VERDICT
AirGradient DIY is a CO2, PM2.5, temperature and humidity monitor you solder from a parts list for roughly 60-90 dollars depending on sensor choices. The same SenseAir S8 CO2 sensor appears in commercial monitors costing 200 dollars+, and the design is fully open under CC BY-SA. Assembly is straightforward — through-hole soldering, clear pinouts, and the firmware flashes over USB — but the enclosure is the weak point: the repo does not include STL files, and the official injection-molded case is not sold separately. Most builders tape it into a project box or leave it bare on a shelf. The reason to build this is the data: CO2 above roughly 1,400 ppm measurably impairs focus, and a closed bedroom with two people can hit 4,000 ppm by morning. The live dashboard makes it visceral. The one thing most likely to go wrong is buying a counterfeit SenseAir sensor from an unknown supplier — the 40 dollars you save disappears when the readings drift within a month.
IN THE REPO
NOT IN THE REPO
- —Full Arduino firmware, detailed assembly instructions, and BOM are in the repository.
- —PCB Gerbers are available; you order the board from JLCPCB or similar.
- —No 3D-printed enclosure files in the repo — the official kit uses an injection-molded case you cannot easily replicate.
- —Licence is CC BY-SA 4.0 for hardware, GPL-3.0 for firmware — both permit commercial use with attribution and share-alike.
- —The company sells pre-made kits and assembled units; the DIY version uses the same sensors but you source and solder everything yourself.
- —Live dashboard requires creating a free account on airgradient.com or running your own server.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
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Videos
An ACTUALLY smart air quality monitor (it's open)
No official build video in the payload; Jeff Geerling's video mentioned in the story summary was not provided as a source link.
Gallery
Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the assembly instructions in the repository README and choose your sensor configuration (basic CO2-only or full PM2.5 + CO2 + temp/humidity). (The BOM and pinout diagrams are clear; decide on sensors before ordering anything.)
- 2.Order the PCB Gerbers from JLCPCB or another fab (files are in the hardware folder) and source the sensors — buy the SenseAir S8 from a reputable supplier, not the cheapest listing.(Counterfeit CO2 sensors are common and drift badly; spend the extra $10 for a known vendor.)
- 3.Solder the components following the assembly guide, flash the firmware via Arduino IDE, and connect to the AirGradient dashboard or your own MQTT broker.(The firmware setup is well-documented; WiFi credentials go in via a web interface on first boot.)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
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KNOWN ISSUES
- Buying a counterfeit or no-name SenseAir S8 sensor to save $10 — it will drift within weeks and the whole build becomes useless data.
- Expecting an enclosure STL in the repo — there is none, and the official case is not sold separately; plan for a project box or bare mounting.
- Assuming the free dashboard will work without an account — you either create one on airgradient.com or run your own server; there is no offline-only mode with the display alone showing history.
- Ordering only one PCB and discovering a soldering mistake — JLCPCB ships five boards for the minimum price, use that.
- Not checking the ESP8266 vs ESP32 firmware differences before flashing — the repository has separate branches and the wrong one will not boot.
- Underestimating how often you will obsess over the numbers — seeing your bedroom hit 3,000 ppm CO2 makes you open windows at 2am, every night, forever.
Can I build this without the PM2.5 sensor to save cost?
Yes — the firmware supports a CO2-only configuration with just the SenseAir S8, temp/humidity sensor, and display. You will spend roughly $50-60 instead of $80-90.
Does the display show live readings without the cloud dashboard?
Yes — the OLED shows current CO2, PM2.5, temperature, and humidity in real time. The cloud dashboard adds historical graphs and multi-room comparison, but is not required for basic operation.
How does this compare to a commercial monitor like Aranet4?
The SenseAir S8 sensor is the same class (NDIR) as the one in the Aranet4, and the PM2.5 Plantower sensor is widely used in research-grade monitors. You lose the polished enclosure and battery power, but the readings are equivalent and you can see the data live on a dashboard instead of only on the device.
What is the actual CO2 threshold where I should open a window?
Outdoor air is roughly 420 ppm. Below 1,000 ppm is comfortable, 1,000-1,400 ppm is tolerable, above 1,400 ppm cognitive performance measurably drops, and bedrooms routinely hit 2,000-4,000 ppm overnight with the door shut. The linked study found 4,000 ppm in a closed bedroom with two people.
Community builds
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Discussion1
FROM THE COMPAREE TEAM
Bedrooms hit 2,000-4,000 ppm CO2 overnight with the windows shut — and the threshold where focus drops is roughly 1,400 ppm. How long did it take before you started opening windows at 2am?
AirGradient
AirGradient is a company and open-hardware project founded to make air quality monitoring accessible. They sell kits and assembled units commercially, but publish the full designs under CC BY-SA so anyone can build from scratch.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM23d agoedited
Practical notes from our verification: the repository is active and well-maintained, with separate firmware branches for ESP8266 and ESP32 builds. The BOM is complete and the assembly instructions are clear, but there are no enclosure STL files — builders either use a generic project box or mount the board bare. The Instagram reels show the official injection-molded case, which is not available separately for DIY builds. The SenseAir S8 sensor sourcing is the single biggest trap: counterfeit units are common on marketplaces, and a bad sensor makes the whole build pointless. The free dashboard requires an account on airgradient.com; self-hosting is possible via MQTT but not documented in the main README.