The air we breathe is invisible, but its quality is fundamental to our health and well-being. As awareness of air pollution grows, so does the demand for accurate, accessible, and reliable data. At Airly, we believe that it’s possible to turn data into clean air, but it requires smart technology, thoughtful deployment, and, crucially, trusted guidance.

That’s why we were really excited to see the British Standards Institution (BSI) developing a new code of practice – PAS 4023:2023, “Selection, deployment and quality control of low-cost air quality sensor systems in outdoor ambient air – Code of practice.”

In this article, we’d like to explain why it’s so important for air quality monitoring and how Airly is helping shape the future of air quality monitoring. Whether you’re AQ Officer at city council, AQ consultant or Sustainability Manager, this document will provide a clear framework for ensuring the data they produce is robust and trustworthy.

Demystifying PAS 4023: what does it mean?

Historically, air quality data came from expensive, stationary reference-grade monitors. While accurate, they’re limited in number and expensive to maintain. Emerging technology of small sensor systems (which are compact, accessible, and scalable) can fill in the gaps, especially in underserved communities.

But with innovation comes responsibility. How do we ensure these devices are trustworthy? How do we deploy them for maximum impact? That’s what PAS 4023 is here to answer. In simple terms, it’s a comprehensive guide for anyone using low-cost sensors to monitor outdoor air quality. It provides recommendations on everything from choosing the right sensor to ensuring the data collected is of high quality.

The standard empowers a wide range of users (local authorities, businesses, scientists, environmental consultants) to implement effective air quality monitoring campaigns. Sponsored by the DEFRA, it’s not a legal requirement, but it’s rapidly becoming the benchmark for best practice. PAS 4023 helps to change that by providing a structured approach to a measurement campaign, broken down into key stages:

1. Designing your campaign: The standard highlights the importance of having a clear goal (identifying pollution hotspots, assessing the impact of a new traffic scheme, or simply raising awareness, etc.) as your objective will shape the entire project.
2. Selecting the right tools: Not all sensors are equal. PAS 4023 provides guidance on selecting sensors that are appropriate for your specific needs (pollutants you want to measure, sensor accuracy, the expected concentration levels).
3. Correct deployment: Where you place your sensors matters. PAS 4023 offers best practices for sensor deployment to ensure they collect representative data (mounting height, avoiding areas with poor air circulation etc.).
4. Ensuring accuracy through calibration and maintenance: PAS 4023 outlines crucial quality assurance processes to ensure the data generated is accurate and reliable (incl. regular calibration and maintenance of the sensors). The document also mentions using co-location and network calibration techniques.

The standard also highlights common challenges, like sensor drift, noise, or interference, and how to tackle them.

How Airly aligns with PAS 4023

At Airly, we don’t just see this new standard as a set of guidelines to follow; we see it as a reflection of the principles we’ve championed from the very beginning.

Here’s how we meet and exceed PAS 4023’s recommendations:

1. 1. Sensor selection
      We understand that the journey to cleaner air starts with the right technology. Our MCERTS-certified sensors are engineered for accuracy and reliability, capable of measuring a wide range of pollutants. We work collaboratively with our partners to understand their unique needs, setting together campaign goals, and ensure the selection of the most appropriate sensors. Our team provides expert guidance on network design and sensor placement too.
   2. Sensor deployment
      From urban canyons to rural landscapes, we follow strict site selection criteria to ensure optimal placement and performance – including factors like airflow, height, obstructions, and risk of tampering. Our installations meet PAS 4023’s deployment guidelines.
   3. Sensor calibration
      Our sensors are rigorously calibrated to ensure the highest level of accuracy. Our calibration processes, which can be tailored to local conditions, are designed to give you data you can act on with confidence. PAS 4023 prioritizes co-location calibration and ongoing network calibration. Airly uses both. You can read more about it on our Quality & Certificates subpage.

What it means for you

Whether you’re a municipality planning a low emission zone, a school wanting to monitor playground pollution, construction site manager complying with regulations, or a business demonstrating ESG leadership, PAS 4023 provides the framework to ensure data you can trust. And with Airly, you’re not starting from scratch – you’re working with a partner who already meets the standard.

We work hand-in-hand with 800+ customers – local governments, businesses, and community groups to build dense, hyperlocal air quality networks. You can read more about our Case Studies.

We believe that introducing PAS 4023 is an important step in air quality monitoring. It’s a clear sign that small sensors can (and should) drive meaningful change. But small sensor providers have to follow the highest standards.

You can learn more about PAS 4023 – Low-Cost Air Quality Sensor Systems in Outdoor Ambient Air under this link: https://www.bsigroup.com/en-CZ/insights-and-media/insights/brochures/pas-4023-low-cost-air-quality-sensor-systems-in-outdoor-ambient-air/.