Estimate the impact of air filter units in your classroom

The CHEPA (Classroom HEPA) impact calculator is a tool that helps estimate how an air filter unit could impact air quality and energy consumption in a classroom. It’s free, quick to use, and designed for non-experts.

Improving classroom air quality

HEPA stands for ‘High-Efficiency Particulate Air filter’. HEPA filter units (or other air filter units containing similar high-performance filters - which for ease we’ll just refer to as HEPA filter units) can help improve classroom air quality. These units are designed to capture very small particles from the air, like dust, pollen and even viruses; you can find more information and videos on air cleaners and filters in schools on our web pages.

Before considering a HEPA filter unit, you should explore if better ventilation practices could improve classroom air quality. Ventilation is the process of refreshing the air we all breathe indoors with air from outdoors. You can find out more about classroom ventilation on our web pages, from the Department for Education guidance, and from the joint union guide at the National Education Union website. The CHEPA impact calculator is only designed for classrooms naturally ventilated by opening windows and doors, and there are also practical factors and other costs to consider when deciding whether to add a HEPA filter unit - these will be highlighted alongside your results.

Frequently Asked Questions

The CHEPA impact calculator is designed to support the decision making of classroom staff, school leaders, and authorities by helping them explore the potential benefits and considerations of using HEPA filter units in classrooms. The tool doesn’t tell you whether you should install a HEPA filter unit.
The CHEPA impact calculator asks straightforward questions about a classroom, such as its floor area and height, the number and age of the pupils using it, and how well it holds in heat. No technical knowledge is needed to answer. Based on this information, the tool estimates the impact of adding a HEPA filter unit on that classroom’s air quality and energy use.

The tool is suitable for most UK classrooms that are regularly used by a single class. It assumes the classroom does not already have a HEPA filter unit or other air-cleaning device, and is built to assess naturally ventilated classrooms only (where fresh air enters the room through windows and doors, not by mechanical means). More details on how the calculator works can be found on our ‘About the CHEPA model’ page
Yes, the calculator is freely available to everyone. You will need to answer practical, observation-based questions about a classroom that you want to assess. The questions focus on how the room is used, how it’s built, and what’s in it and have been designed so that anyone familiar with classrooms in the UK can easily give estimated answers. While you are welcome to use estimates, more accurate inputs will give you more precise results.

It’s especially useful if you already have an idea of the type of air filter unit that you are considering, as it can help you assess how well it might perform in a specific classroom setting. The calculator only takes a few minutes to complete and it is simple to edit your previous answers to see how it changes the results.
Your data is used solely to generate your results and it is not used for any other purpose. If you accept the use of local storage via our cookies policy, your data will be stored locally within your browser allowing you to return to the tool and pick up where you left off. If you have any questions or concerns relating to your data, please get in touch by email.
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