The Mayor's School Filters Programme

The Mayor’s School Filters Programme is one of the UK’s largest school-based indoor air quality projects. Backed by the Greater London Authority (GLA), the programme will deliver air filters (also referred to as air purifiers), air quality monitors and assemblies and workshops on air quality to over 200 primary schools across London. Led in partnership by Smart Air UK, WSP, and Walk Wheel Cycle Trust (formerly Sustrans), the programme aims to reduce children’s exposure to air pollution, especially for schools in areas of poorer air quality and higher deprivation.

Smart Air UK is providing the air purifiers/air filters and air quality monitors
Walk Wheel Cycle Trust (formerly Sustrans) is leading the engagement with schools, managing sign-ups and delivering assemblies and workshops on air quality
WSP to provide air quality monitoring and evaluation, and maintenance support through extent of study period ending April 2027

Why this programme is needed

Air pollution is the largest environmental risk to public health in the UK. Children are especially vulnerable because they breathe faster, spend more time indoors, and have developing lungs. This programme targets schools in communities where children are more likely to breathe polluted air.

In 2019, no primary school in London met the WHO’s evidence-based guideline for PM2.5.
Children in deprived areas are five times more likely to attend schools in polluted locations.
PM2.5 has been linked to asthma, stunted lung growth, heart disease, and reduced school attendance.

What the programme delivers

Children spend over 30 hours a week in classrooms. Cleaner air helps reduce illness, supports concentration and can improve school attendance. The Mayor’s School Filters Programme brings a full clean air package to over 200 London schools. Here’s what’s included:

Air filters for classrooms in over 200 London schools: Every classroom will be fitted with a high-efficiency air purifier to reduce harmful indoor pollution.
Units will be equipped with timer switches, programmed to run for eight hours a day, five days a week, matching the school day while reducing energy use and fire risk.
Schools are chosen using modelled pollution data and indices of deprivation, helping schools which could benefit the most.
Two indoor air quality monitors per school measuring PM2.5 and CO₂:
- There will be a control classroom with no air filtration and one with the filters running
- The chosen monitor is from AirGradient
- Each school will receive 2 indoor air quality monitor
Clean air workshops will be available to teach teachers and students about air pollution. This will be done by way of interactive assemblies and classroom sessions to help raise awareness and promote clean air behaviours.

How it will be measured

The programme includes a full monitoring and evaluation plan to understand its impact and inform future action:

Reductions in PM2.5 levels inside classrooms: Air quality monitors will track changes before and after filter installation, with a focus on lowering harmful particulate levels.
Feedback from schools on noise, ease of use and effectiveness: Schools will provide practical feedback on how the units are working in real settings, including usability and any disruption.
Attendance and engagement data from pupils: Where available, data will be reviewed to explore any links between improved air quality and pupil attendance or wellbeing.

The evaluation of the programme may inform the further rollout of filters across London.

In its current state, the monitoring, maintenance and support period for this programme lasts until Spring 2027. Schools will be able to keep their filters and monitors after this period.

If you have any questions on this project, please email [email protected] referencing “The Mayor’s School Filters Programme".