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A 60 DOLLARS DIY MONITOR SHOWS WHY YOU'RE TIRED AT HOME — CO2 DOESN'T LIE

A soldered air quality monitor that shows how fast CO2 builds up in a closed bedroom overnight.

by AirGradient

FULL CAD BOM FIRMWARE DOCS

HomeHealth

Built withESP8266Arduino

difficulty
●●○○○
time
an evening
license
CC-BY-SA-4.0
repo
repo ACTIVE382 stars

WHAT YOU’LL NEED

Videos
1
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COMPAREE VERDICT

AirGradient is a company that open-sources its air quality monitors, and its DIY Basic build lets you put together a CO2, PM2.5, temperature and humidity monitor yourself: a Wemos D1 Mini, a SenseAir S8 CO2 sensor, a Plantower PMS5003 particle sensor, an SHT3x or SHT40 module and a small OLED on a custom PCB. The firmware is on GitHub; the build guide, Gerber files and a printable STL enclosure are on AirGradient's documentation site. Note that AirGradient lists the DIY Basic and DIY Pro boards under old designs that are no longer maintained, and its guide says you need good soldering skills. The monitor shows readings on its display without any account, can send data to the AirGradient dashboard or another backend, and exposes a local API. A solid, affordable way to see what the air in your home is actually doing.

GOOD TO KNOW

  • —Full Arduino firmware is in the repository; build instructions and parts lists are in the AirGradient documentation.
  • —PCB Gerbers are available; you order the board from JLCPCB or similar.
  • —No enclosure files in the firmware repo, but AirGradient publishes printable STL enclosures on its documentation site.
  • —Licence is CC BY-SA 4.0 — it permits 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.

Parts to buy

6 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • PCBfrom the repo files
  • Wemos D1 Mini (ESP8266)Find
  • Wemos OLED displayFind
  • SenseAir S8 CO2 sensorFind
  • SHT3x or SHT40 temperature/humidity moduleFind
  • Pin headers and wireFind

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Can I build this?

Printoptional — AirGradient's printable DIY enclosure (STL on its documentation site), or use a project box
BuyPCB (order it from the Gerber files AirGradient publishes, or buy one from AirGradient), Wemos D1 Mini (ESP8266), Wemos OLED display, SenseAir S8 CO2 sensor, Plantower PMS5003 PM sensor with an 8-pin cross-over cable and JST connector, SHT3x or SHT40 temperature/humidity module, pin headers and wire
Toolssoldering iron, solder, USB cable for flashing, Arduino IDE or PlatformIO
SkillsGood soldering skills (AirGradient's own guide says so) and Arduino or browser-based firmware flashing; some Wemos D1 Mini and OLED clones are unreliable, so buy from a decent seller.
Timean evening to solder and flash, plus ordering time for the PCB and sensors
Cost$$ — AirGradient's guide lists typical prices of about 2-4 dollars for the D1 Mini, 2-3 for the OLED, 15-20 for the PMS5003, 25-30 for the SenseAir S8 and 3-5 for the temperature/humidity module, plus the PCB and enclosure; the S8 is the single most expensive part.
SafetyNone beyond ordinary electronics care — low voltage DC only, no mains, no lithium cells in the basic design.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

Videos

An ACTUALLY smart air quality monitor (it's open)

A Geerling Engineering video about AirGradient monitors installed in an office — an overview, not a build guide. For assembly, AirGradient's guide links Jeff Geerling's DIY Basic build video (earlier PCB version).

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Gallery

Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Read AirGradient's DIY build guide for your PCB version on its documentation site and choose your sensor configuration before ordering anything. (The build guide lists every component with typical prices and links to the schematic, Gerber files and enclosure STL; the GitHub repo holds only the firmware.)
  2. 2.Get the PCB (AirGradient sells DIY PCBs and kits via airgradient.com) and source the sensors — buy the SenseAir S8 from a reputable supplier, not the cheapest listing.(Buy the SenseAir S8 from a reputable supplier; AirGradient's guide lists typical prices of 25-30 dollars for it.)
  3. 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.

KNOWN ISSUES

  • Buying the cheapest no-name modules — AirGradient reports that some Wemos D1 Mini and OLED boards froze or behaved unexpectedly, and it cannot guarantee third-party modules.
  • Looking for the enclosure in the GitHub repo — it isn't there; the printable STL is on AirGradient's documentation site, or use a project box.
  • Expecting history graphs on the device itself — offline it only shows live readings; for history you need the AirGradient dashboard (free account), your own server via the local API, or a platform such as Home Assistant.
  • Ordering only one PCB and discovering a soldering mistake — JLCPCB ships five boards for the minimum price, use that.
  • Not installing exactly the library and board versions named in the example sketch you use (BASIC for the DIY Basic board) — the README warns about this, and older PCBs need library version 2.4.15.
  • 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 — AirGradient's guide says you do not need to fit every sensor. Leaving out the PMS5003 particle sensor saves its typical 15-20 dollars, and the S8, temperature/humidity module and display still work.

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?

Both use NDIR CO2 sensing, but AirGradient's guide makes no accuracy comparison with commercial monitors such as the Aranet4. The DIY build adds a PM2.5 sensor and open data; you give up a polished, battery-powered product and must calibrate expectations yourself.

What is the actual CO2 threshold where I should open a window?

Outdoor air is roughly 420 ppm, so indoor readings far above that mean the room is poorly ventilated. Use the trend on the display: if CO2 keeps climbing while you are in the room, open a window or increase ventilation.

Community builds

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Discussion1

FROM THE COMPAREE TEAM

Once you can watch CO2 climb in a closed bedroom overnight, what would you change first: the window habit, the ventilation, or where the monitor sits?

CompareeTEAM2mo agoedited

Practical notes from our verification: the GitHub repository is the firmware library, one codebase for the ESP8266 (Wemos D1 Mini) and ESP32-C3 boards, with compilation, over-the-air update and API documentation. The build guides, kits and parts lists live on airgradient.com/documentation, so that is where you start the hardware side. AirGradient also publishes 3D printer files for a DIY enclosure, so you are not stuck with a bare board. The sensor line-up is explicit: Plantower PMS5003 for particles, SenseAir S8 for CO2, and Sensirion SGP41 and SHT40. You do not have to use the cloud: the monitor exposes a documented local server API, and the AirGradient dashboard is the optional hosted route. The README warns to install exactly the library and board versions named in the example files, and skipping that step is the easiest way to end up with firmware that will not compile. The firmware is licensed CC BY-SA 4.0. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.

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.

GitHub

Star the project on GitHub

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.
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