Air Quality Assessment Guide

Poor air quality is a major public health issue, and long-term exposure to air pollution is linked to a wide range of serious health conditions. The government estimates between 28,000 and 36,000 deaths occur every year in the UK due to human-made air pollution.

To tackle this, there is a wide range of measures implemented in the UK for pollution control. A well-known case is London’s Ultra Low Emission Zone (ULEZ), which aims to reduce the number of vehicles and encourage upgrading vehicles to comply with emission standards. Air Quality Assessments are also methods used to reduce air pollution.

Air Quality Assessments can be split into two types: indoor and outdoor. Both are important and have different use cases. For example, indoor assessments are needed once a development is finished, whilst outdoor assessments focus on pre-construction and are commonly required in planning applications.

In this article, we will focus on the outdoor Air Quality Assessment.

Understanding Air Quality Policy

Air Quality Assessments are taken in accordance with National and Local Planning Policy. Part IV of the Environment Act (1995) requires the UK government to produce a national Air Quality Strategy, which contains standards, objectives, and guidelines for improving ambient air quality.

These air quality standards were produced by DEFRA and published on 28th April 2023. The Air Quality Strategy sets out Air Quality Objectives (AQOs). These are maximum ambient pollutant concentrations which are not to be exceeded either without exception or with a permitted number of exceedances over a specified timescale.

AQOs provide the basis on which we judge Air Quality Assessments. Whether a development falls below or above these thresholds largely influences what level (if any) of air quality mitigation is required.

In the UK, the most common pollutants are NOx, PM10, and PM2.5, and the main contributor of these pollutants is motor vehicles. As such, Air Quality Assessments typically focus on these pollutants and the impact motor vehicles generated by a development have on surrounding air quality.

Air quality policy and legislation are dynamic, constantly evolving with scientific breakthroughs and growing social awareness. For example, most people are now familiar with the Air Quality Index.

The World Health Organisation’s Air Quality Guidelines state there is no “safe” level of air pollution, so there is a lot more work to be done in the UK. As such, we anticipate these thresholds to become stricter, and assessments to become more essential to planning applications in the years to come.

What is an Air Quality Assessment?

Air Quality Assessments can be categorised into two types: Baseline and Dispersion.

All assessments contain a Construction Phase Dust Assessment, which is used to estimate impacts and provide mitigation measures to minimise dust emissions during the construction phase.

For Air Quality Assessments in London, there are additional requirements of being Air Quality Neutral or Air Quality Positive. This is determined by comparing the development’s generated emissions against Transport and Building Emission Benchmarks (TEB & BEB).

Baseline

Baseline assessments do not contain a dispersion model and are typically used on smaller developments where it has a low impact. In these assessments, we look at the baseline conditions of the site and assess the need for a further assessment (i.e., Standard or Impact).

A further assessment is determined if anticipated traffic exceeds screening criteria and if there is potential for future occupants to be exposed to unacceptable levels of air pollution. In these assessments, nearby air quality monitors, background concentrations, and site context are used to provide an estimate of what conditions will be like on site.

Dispersion

For larger developments or in areas where air quality is particularly bad such as Air Quality Management Areas (AQMAs), we need a more accurate view of the expected air quality concentrations on site, so we build a dispersion model.

Dispersion model assessments can be categorised as Standard or Impact assessments. The Standard Air Quality Assessment report predominantly focuses on the on-site conditions. The results from the dispersion model are compared to the AQOs; this determines whether a site requires mitigation measures and if a further Air Quality Impact Assessment is required. Air Quality Impact Assessment reports are the most extensive and also consider the impact of a development at sensitive receptors within the vicinity of the development.

Dispersion Modelling – How Does it Work?

The dispersion model takes several data sources and models how air pollutants move and spread through the atmosphere. It is used to provide a more accurate view of what we expect pollutant concentrations to be like both at the development site and at surrounding sensitive receptors—such as residential areas, schools, or hospitals.

To do this, the model uses a combination of inputs, including:

PM2.5 Concentration Heatmap Figure

• Meteorological data (typically a year’s worth of hourly data from a nearby weather station) to account for wind speed, direction, temperature, and atmospheric stability.

• Traffic data to represent the number, type, and speed of vehicles expected to use local roads once the development is operational.

• Topographical data which affect how pollutants disperse in real-world settings.

• Monitoring data which is used to verify the dispersion model against real world conditions to ensure it is functioning accurately.

  
  

The most commonly used model in the UK is ADMS, although other models such as AERMOD are used in some contexts.

Air Quality Mitigation Measures in Developments

When developments exceed Air Quality Objectives (AQOs), developers must implement mitigation measures to reduce or offset their impact on air quality.

These measures can be wide-ranging and are typically tailored to the source and scale of the expected emissions. The financial impact of air quality mitigation is typically quantified using a DEFRA Damage Cost Assessment.

Internal mitigation measures aim to reduce pollutant exposure once the development is occupied. These can include the use of mechanical ventilation with filtration, sealed windows, or locating intake vents away from pollution sources such as busy roads. In some cases, green walls or vegetation barriers are used to enhance natural filtration.

External mitigation addresses the emissions generated by the development itself, most commonly from increased vehicle traffic. Typical strategies include:

• Provision of Electric Vehicle (EV) charging infrastructure

• Designing developments to encourage active travel (walking and cycling)

• Upgrading local roads to improve traffic flow and reduce idling

• Incorporating low-emission boilers or heat pumps instead of gas heating

  
  

In London and other high-risk areas, developments may also need to contribute to offsetting funds or achieve Air Quality Neutrality.

Ultimately, the goal of air quality mitigation is to ensure the development does not worsen air quality for existing or future residents and ideally contributes to a net improvement.

The Future of Air Quality Assessments

Traditionally, Air Quality Assessments have been time-consuming and prone to error, requiring extensive manual data handling. To address this challenge, we developed software to streamline the entire assessment process, from quote to report.

We wanted to revolutionise how an Air Quality Assessment is completed. After reviewing feedback from clients, we found their top priorities boiled down to three things: Speed, Price, and Quality.

Speed

One of the most common questions clients ask is: “How long will it take?” or “Can you complete it in [X] time?”—only to be disappointed when hearing it would be much longer than expected.

We understood that clients value quick turnarounds and identified several areas in the assessment process that could be streamlined or automated. So, we built software specifically to target these repetitive, manual stages.

Result: We have now cut assessment time on average by 80% and lead the industry in turnaround times.

Price

It is no surprise that Air Quality Assessment cost is an important factor when clients consider what makes an assessment great.

Through the significant automations made with our software, we have been able to make the cost of completing assessments much cheaper. This has enabled us to offer clients the most competitive pricing in the industry.

Result: Industry-leading prices and the first free Air Quality Assessment service.

Quality

By developing streamlined, automated methodologies, we’ve improved both the accuracy and reliability of assessments.

Traditionally, Air Quality Assessment consultants manually estimate key inputs like vehicle speeds and road widths—a process prone to inconsistency and human error. Our system eliminates these risks by automatically pulling precise, verified data from multiple authoritative sources.

We also store all data within our system to auto-populate an Air Quality Assessment template, further reducing the likelihood of human error when inputting data.

Result: We can now model more accurately than ever before, and our reports contain fewer mistakes.

Conclusion

The future of Air Quality Assessments lies in speed, affordability, and accuracy—and we're proud to be leading that transformation. By listening to our clients and building purpose-built software, we've redefined how air quality assessments are completed. Our system dramatically reduces turnaround time, lowers costs, and improves reliability by eliminating manual errors and streamlining every step of the process.

Do you need an Air Quality Assessment for planning? Contact us today for a free quote.