AirGradient Open Air - The Climate Change Monitor

Outdoor Air Quality Monitor

Open Air (Model O-1PST) is an outdoor air quality monitor enabling you to know if the air quality is healthy or not. It measures PM1, PM2.5, PM10, CO2, TVOCs, NOX, Temperature and Humidity.

It’s fully open-source and customizable, so you can extend it in whatever way you like.

Get It From Us
Community Spotlight

Adsing Bangkok's Air Pollution Crisis: Efforts in Protecting Children Through Dust-Free Classrooms

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Air Pollution and Climate Change are Two Sides of the Same Coin

According to the World Health Organization, more than 90% of the people breathe unhealthy air. Air pollution is the biggest driver of premature death of all environmental health risks. With climate change and the warming of the planet, air pollution, e.g. through wildfires are also increasingly becoming a major issue in regions with previously very clean air.

Air quality can quickly fluctuate between good and unhealthy levels and thus a dense network of air quality monitors ensures that people know when they need to protect their health. The Open Air outdoor monitor keeps you always informed about the air you breathe.

The Open Air is one of the first low-cost air quality monitors that includes a CO2 sensor which allows the identification of local emission sources -which might not always emit large amounts of particles and therefore not always visible with the PM data.

What does it Measure?

The monitor measures PM, CO2, TVOCs, NOX, Temperature and Humidity.

The PM sensor (Plantower PMS5003T) measures particulate matter, especially smaller particles like PM1 and PM2.5 have the potential to cause significant harm to our well-being. These tiny particles are released into the air through various sources such as vehicle emissions, industrial activities, burning of fossil fuels or wildfires. When inhaled, these small particles can penetrate deep into our respiratory system, leading to a range of health issues. Long-term exposure to PM2.5 has been linked to respiratory and cardiovascular diseases, including asthma, bronchitis, heart attacks, and even premature death.

The CO2 sensor (SenseAir S8) can give you valuable information about local emission sources. These elevated CO2 levels can then also indicate other harmful gases that are often emitted with CO2 like SO2, NO and NO2. These emissions are not always visible with only measuring PM due to for example good filters in power plants or factories. Another use case is to detect leakage from underground carbon storage facilities. Please note that the sensor is not accurate enough to measure the exact atmospheric CO2 increases (currently around 430ppm), however our tests show a very high agreement with reference instruments.

The monitor also includes the Sensirion SGP41 TVOCs, NOX sensor. This sensor shows relative spikes in total volatile organic components and NOX based on the Sensirion VOC Index. Even though VOCs are typically associated with indoor sources, VOCs can also occur outdoors for example emitted from chemical factories, petrol stations, natural gas leakages, burning of garbage etc. Please note that VOCs are also triggered by harmless substances like ethanol or sunscreen. So an elevated value does not necessarily mean a harmful event.

We work very closely with a number of leading universities on air quality monitoring and our monitor has been selected for the largest study of classroom air quality in the world due to its performance and affordability. You can read more about our work with research institutions on our research page.

Flexible Data Platforms

The AirGradient Open Air monitor is unique as it gives you full flexibility on how you want to monitor and use the data. Being open-source you are not locked in to any specific data platform but can connect the data to any server, i.e. Home Assistant or use the AirGradient data platform - a data platform specifically made for air quality monitoring.

This gives you complete ownership and freedom of your data and our community has built a number of extensions to existing data platforms, e.g. home assistant with ESPHome.

Of course you can also use the AirGradient dashboard that is already pre-flashed on the monitor and very easy to setup.

This powerful dashboard lets you immediately see the air quality and environmental status of multiple locations. Built for speed and scale. You can set up specific alerts and are notified automatically if air quality is exceeds your defined ranges.

Get powerful daily and weekly reports detailing the air quality of each location, providing you with a clear, concise summaries at a glance.

Outdoor monitors can also be displayed on the AirGradient Map and you can opt-in to share your outdoor data with openAQ, a non-profit with the mission to democratize air quality data and make it freely available.

AirGradient Map with OpenAQ Data

If you use the AirGradient data platform, you can opt-in to share your outdoor data with the public and openAQ. OpenAQ is a non-profit organisation collecting and organizing worldwide air quality data and making it available for the public and research. Your data is then also available on the AirGradient map together with thousands of other monitors from openAQ.

Easy to Assemble, Setup & Install

The kit version is very easy to assemble, and you can also get the monitor as fully assembled version. We provide detailed instructions and videos on how to connect the monitor to your WiFi network and set it up on the dashboard and map. If you run into any problem, just contact us directly and we are happy to help. You can also ask questions in the AirGradient Forum and get valuable tips from the community.

Mounting Options

The monitor can be mounted on walls or poles. For pole mounting, use two stainless steel zip ties and feed them through the zip tie holders. Alternatively you can use two screws and mount the monitor on a wall. To prevent theft, there is a small hole on the monitor that you can use with a secure screw to prevent the monitor from easily taken off.

The enclosure is fully weather proof so it can be mounted being exposed to the elements.

Optimized Enclosure

The enclosure has been designed with two primary goals, firstly to ensure accurate measurements of the air quality and secondly to be robust and long lasting.

For accurate measurements it is important that there is a good airflow to the sensor modules, that air loops in front of the sensor modules are avoided and that the risk of condensation inside the enclosure is as much as possible reduced.

The enclosure itself is very robust and consists of high quality ASA plastic that gives an excellent durability as well as UV protection.

Get the AirGradient Open Air

Being open-hardware, you can either build the monitor on your own, or purchase it as a kit or fully assembled unit with warranty and test report from our online shop

Open Air

AirGradient PRO Fully Assembled

Outdoor air quality monitor. Measures PM1, PM2.5, PM10, CO2, TVOCs, NOX, Temperature and Humidity. Fully assembled and tested.

Open Air

  • Model O-1PST
  • Measures PM, CO2, TVOCs, NOX, Temperature and Humidity
  • 4m USB C cable (w/o power plug)
  • 24 months AirGradient data platform with map (or connect it to your own server, e.g. home assistant)
  • Fully open-source code so you can easily make adjustments
  • Fully assembled
  • Tested in our test chamber with test report
  • Certified: CE, FCC, RoHS, REACH
  • 12 months warranty

USD 190.00

Buy Now

Also available as Kit for:
USD 125.00

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Technical Data

Below is the technical data of the default version of the Open Air as it is available in our online store.

O-1PST (AirGradient Open Air)
ESP32-C3-MINI (32-bit RISC-V single-core processor, up to 160MHz, 384 KB ROM, 400 KB SRAM, 8 KB SRAM in RTC, 4 MB flash in chip package)
2.4GHz IEEE 802.11 b/g/n-compliant
Bluetooth LE: Bluetooth 5, Bluetooth mesh
Broken out on PCB: I2C, 3 GPIO, 2 UART
Status LED, Push Button, USB C Connector
External Hardware Watchdog
Texas Instruments TPL5010
Particle Sensor Module
Plantower PMS5003T (laser scattering principle). Accuracy: ±10%@100~500μ g/m³, ±10μg/m³@0~100μ g/m³
Temperature and Humidity
ENS210 (inside PMS5003T module). Accuracy: Temperature ±0.2°C @ 0 - 70°C; Humidity ±3.5% RH @ 20 - 80% RH
CO2 Sensor Module
SenseAir S8 (NDIR). 0 to 10000ppm. Accuracy: ±40 ppm ±3% of reading at 5 to 30°C, 0-85% RH (400 - 2000ppm range)
Sensirion SGP41. Accuracy: TVOC <±15 @ 0 to 500 VOC Index; NOX <±50 @ 0 - 500 NOX Index
ASA Plastic, UV Resistant and Weather Proof
Mounting Options
Wall or pole mounting options
4m USB C Cable including Data Lines for Flashing
Power Plug (not included)

2A 5V USB A Power Plug is Required


Ideally combined with indoor monitors

In order to fully understand the air quality of your environment, we recommend you also monitor the air quality indoors. We spend most of our time indoors and often the indoor air can also be very unhealthy due to indoor pollutants like volatile organic components (VOCs), or high particle concentrations from cooking. High CO2 values due to insufficient ventilation can lead to tiredness and lower cognitive performance.

By monitoring both, indoor and outdoor air quality you get valuable additional data, e.g. where the pollution is coming from, how well does the ventilation and air purification of your home works etc. The AirGradient dashboard is especially suited to compare indoor and outdoor air quality in combined reports and charts.

Go to our indoor air quality monitor page to learn more about our open-source indoor monitors.

In 2019, 99% of the world population was living in places where the WHO air quality guidelines levels were not met. Ambient (outdoor air pollution) in both cities and rural areas was estimated to cause 4.2 million premature deaths worldwide in 2016.

World Health Organisation

Easy to Extend

The open-hardware / open-source nature of the monitor allow easy changes and additions on the firmware as well hardware. The board is powered by an ESP32-C3-MINI microcontroller that is easy to program with a wide eco-system and has integrated WiFi and Bluetooth capabilities.

The ESP32 can directly be flashed through the USB C port and thus changes in the open-source firmware can easily be done.

For the ones, who would like to make adjustments to the monitor, there are breakout pins available for I2C and three additional IOs. In addition, you can repurpose the two UARTs. The board provides both, 5 and 3.3 volts.

We integrated an external hardware watchdog chip that automatically reboots the unit in case something goes wrong and thus the monitor can achieve high up times.


We are very thankful for the overwhelming support we get for the AirGradient air quality monitors and are especially thankful for people that write about their experiences using the monitors. Below is a wide range of reviews from AirGradient users!

BreatheSafeAir on the AirGradient Open Air

Etahn from BreatheSafeAir wrote a very comprehensive review of the AirGradient Open Air. Read more in: AirGradient Open Air Review – Open-Source Outdoor Air Quality Monitor.


BBC Newsround featured our indoor monitor that is used in the SAMHE project, the largest study on classroom air in the world. A big part of this project is to increase the awareness of healthy air among primary and secondary students.


An article analysing the accuracy of monitors from USD 100 to a few thousand got featured by Hackaday: The Questionable Benefits of Paying More for Air Quality Monitors.

Jeff Geerling on Basic Kit

We are a huge fan of Jeff Geerling YouTube Videos, and he made a fantastic video review when we had only our first air quality kit, the Basic kit. It’s great that he also talks what actually made him want to know more about the air quality in his basement office.

Tyler Cipriani on the Basic Kit

Tyler built the AirGradient to measure smoke from the Canadian Wildfires and also makes has some interesting links in his article, e.g. how air pollution makes chess players make more errors.

Igor Bubelov on DIY Pro and Outdoor Monitor

Igor purchased and reviewed our indoor DIY kit and we liked his unbiased review on our indoor monitor so much that we gave him two outdoor monitors with the hope that he would also write about them. And it actually happened! Read his detailed review on the Open Air.

Nicholas Schmidt on DIY Pro and Outdoor Monitor

Many thanks also to Nicholas who reviewed our indoor and outdoor open hardware kits and wrote about his reasons to know about the air he breathes. By the way, in the meantime we made some changes on the outdoor enclosure and the assembly with the cable management is much easier now.

See The Air Blog on Basic Kit and Display

Sotirios not only wrote about our basic kit but also about our open sourced small information display that is particularly popular with student projects in schools.

Hacker Public Radio

Daniel Persson talks about how he build an AirGradient and could actually now see how fast CO2 increases indoors.

Yosua Ian Sebastian on AirGradient Indoor Kit with Home Assistant via ESPHome

This is a great technical review how Yosua setup our open hardware indoor monitor with his own server based on home assistant.

Thatcher Chamberlin on building the DIY Basic Kit

There are some great programming notes on Thatcher’s blog that covers also his ESPHome installation.

OpenAQ on our Data Sharing Partnership

We are proud being official partner to openAQ and they wrote about our partnership on their blog.

Andrej Friesen on building the Basic Kit

Andrej has a small home office (14 square meters) and build an AirGradient to find out how is the air quality in his home office. Read more on his blog.

SEI Asia Podcast: Monitoring air quality is crucial in the fight against pollution

We talked about the importance of monitoring air quality and the work we do at AirGradient with the Stockholm Environment Institute Asia Centre. Tune in here to listen to it.

Where is Your Review?

If you like our open hardware monitors please spread the news and consider writing a review about them! Since our monitor designs are open and under Creative Common license, and we want honest and unbiased reviews it is against our ethos to pay for reviews. But we would be very happy to support in other ways. Get in touch with us.

Open Hardware, Open Source, Open Data

As the name implies, the Open Air has been designed from the ground up with the strong desire democratizing air quality monitoring. Access to the information about the air you breathe should not be a privilege of the rich. Air pollution is one of the largest global environmental and health risks, requiring a high density sensor network to understand and solve the problem. We provide a blueprint of a robust, affordable and open design that citizens and NGOs worldwide can use to accurately measure air quality.

Fully Open Source

All code, schematics, 3D files etc. are open-source and published under CC-BY-SA 4.0 license. You can easily adapt the hardware as well as flash your own firmware.

You own your Data

There is a trend in our industry to monetize air quality data to the extent that often the owner of the monitor does not own the data. We believe this is wrong. The data that your monitor generates should belong to the owner of the monitor.


We have partnered up with openAQ, a non-profit with the mission to provide air quality data to influence policy, and to enable the public to access information on air pollution through open data and open-source tools.

1% for the Planet

We joined 1% For The Planet and pledged to donate at least one percent of your annual sales to non-profit organisations dedicated to protect the planet. You can read more about our motivation to join 1% for the planet on our plog post ‘Why We Joined 1% For The Planet’


We are fortunate to have such a strong community sharing our mission to bring open, accurate and affordable air quality monitoring to everyone running thousands of open-hardware monitors in more than 70 countries around the world.

Activities and Stories From and About our Community

We are blessed to have such an active community. Read more about community engagement.

More articles on our blog.

Statements from People Involved

Having used the AirGradient indoor DIY kits as well as the commercial AirGradient ONE in awareness projects with schools and universities here in Thailand, I am very keen on piloting this new outdoor monitor. I am also interested in exchanging ideas and resources for student engagement with this open source projct.

The San Joaquin Valley of California has extreme climate injustice and the worst air quality in the United States, yet continues poorly monitored. The SEEN Team has partnered with AirGradient to facilitate low-cost monitoring in rural disadvantaged communities, and to increase awareness and education related to air quality. We intend to provide more and better real-time air quality information for local decision makers to act in the best interest of their underserved communities.

Angel S. Fernandez-Bou, PhD, Central California

I’m very happy to contribute to this open hardware project with my product design experience and working with the team to not only ensuring a beautiful look but a highly functional design. Turning the required air flow characteristics and vent specification into a good looking product was a challenge I really liked. I’m looking forward to see the product in many Citizen Science projects around the world.

Having tested numerous air quality sensors for the projects we are doing I found myself extremely impressed with AirGradient. Not only are they technically first class with their product, they have a level of engagement and adaptability which makes working with them very easy. A welcome element to this is their clear commitment to the importance of environmental issues, showing itself in their interest in the details of our projects - all this helps them to deliver…!

Professor Rod Jones
University of Cambridge

AirGradient have consistently gone above and beyond their contractual duties in order to better support the SAMHE Project. They have shown great flexibility and a genuine interest to listen to the complex needs of the project; as a result, they deliver valuable products and a friendly service, both in a manner that is timely for the project.

Henry Burridge
Imperial College London

The AirGradient Manifesto

This manifesto reflects our core values and the principles we stand for:

Positive Disruptor

We must be bold. We always follow our convictions and call out the issues that matter, sharing our views on topics surrounding air quality and environmental responsibility. We will not compromise for profit. We believe that open, informed, and candid discussions are the catalysts for meaningful change. We will lead by example and become a driving force for environmental monitoring.

Responsible Products

We will deliver benefits for both people and the planet. This is why we prioritise creating high-quality air quality monitors with designs that enable easy repairs and recycling, thereby extending the product’s lifespan and reducing its environmental footprint.

Open Science and Research

Our research is driven by a commitment to environmental protection, not by profits. This is why we don’t patent our air quality monitor designs but on the contrary, share them openly, allowing everyone to build them and to contribute to positive change. We do not lock users into proprietary eco-systems and we encourage sharing of air quality data and algorithms as a public good.

Community Building

We want to raise awareness about air pollution through active community building with a strong focus on informing about the dangers of air pollution. We actively support environmental justice organisations and educational institutions in their missions to provide healthier environments for everyone.

Profit Follows Impact

To deliver positive impacts on the communities, and the environment, we must sustain our business model. However we will not prioritise profits above our convictions. We embed this rationale into our everyday decision-making processes throughout all layers of our company. (e.g. by joining 1% for the Planet).

Transparency and Accessibility

AirGradient is built on a foundation of openness and inclusivity. We aim to make our products and services available to a wide range of users with a special focus on underrepresented communities. We strive to work with all organisations that want to make a positive contribution independent of their financial means.

More articles on our blog.

Why we care about Air Quality

AirGradient started as a volunteer project to help a school in Northern Thailand monitor the air quality in classrooms during the highly polluted burning season. From the beginning, we have worked with students and educators to building hardware to increase awareness in the area of air quality, to understand the health impacts of pollutants, and to empower the positive changes that can be made to reduce air pollution.

The experience and expertise that we gained designing and manufacturing our professional AirGradient ONE RESET Air Accredited Monitor has been put into our open-source / open-hardware air quality build instructions and kits.

The industry-grade sensor modules used in our open hardware monitors are the same modules found in pre-built monitors costing hundreds of dollars. As a result, you get highly accurate data quality, essential to having a reliable understanding of the air around you.

We’ve pledged 1% of sales to the preservation and restoration of the natural environment.