New tool will assess viability of installing air filters in classrooms

A new digital tool has been launched to help schools in the UK make informed decisions about classroom air quality.

The CHEPA (Classroom HEPA) impact calculator is a free, web-based resource which helps users explore whether adding a HEPA filter unit could meaningfully improve indoor air quality and what that might mean for energy use, providing classroom-specific evidence in minutes.

The calculator was designed by researchers at Imperial College London and the Stockholm Environment Institute, working with school leaders, local authorities and national bodies such as Hertfordshire County Council, the Greater London Authority and the Department for Education.

CHEPA was created to offer a simple, reliable way for non-experts to ‘sense-check’ how high-performance air filters might perform in real UK classrooms. Its co-design process was based on the collaborative methods used to build the SAMHE (Schools’ Air quality Monitoring for Health and Education) web app, ensuring the tool reflects the needs and constraints of schools.

After a short series of questions about a classroom (size, insulation, typical occupancy etc) have been answered, the tool will estimate how adding a HEPA filter might reduce particulate matter, lower respiratory aerosol concentrations and affect overall energy consumption.

CHEPA integrates outdoor air quality information from Defra’s Automatic Urban and Rural Network alongside weather data from CIBSE Test Reference Year files to ensure the model reflects seasonal conditions and typical pollutants experienced in British school environments, particularly in classrooms that rely on windows and doors rather than mechanical ventilation systems.

The tool does not recommend whether a school should install a HEPA filter; instead, it provides clear side-by-side comparisons of scenarios with and without a unit, highlighting both the benefits and practical considerations such as energy implications and maintenance needs.

Results are generated instantly and can be downloaded or shared, making the tool suitable for classroom teachers, school business managers, council education teams and organisations overseeing school estates.

Data entered into the calculator is used solely to produce results; if users opt into local storage via their browser, they can return and edit scenarios at any time.