A classroom air quality programme does not need to measure everything — but it needs to measure the right things, and the headteacher needs to know what to do when each one goes amber.
The five channels that matter most.
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CO₂ — the ventilation gauge. Below 1,500 ppm average across an occupied period (DfE upper bound). Action: window rota, MVHR retrofit, occupancy review.
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PM2.5 — particulate matter from outdoor air, dust, sometimes traffic. Below 15 µg/m³ 24-hour mean (WHO 2021). Action: HEPA purifier during outdoor PM events, review proximity to roads at intake.
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Temperature — focus and comfort. 18–22 °C is the target. Below 16 °C: heating issue or excessive ventilation. Above 25 °C: insulation, glazing, fan-cooling.
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Humidity — comfort and mould risk. 30–60% RH. Outside this band: investigate the source (drying clothes, blocked extractor, leaky window seals).
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Sound level — hearing protection in sports halls, gyms and music rooms. Sustained dBA above 85 needs attention. Envora One reports a single dBA number — no audio recording.
What "amber" looks like in practice.
Most classroom programmes set up two thresholds per channel: a "watch" level (action needed within the day) and an "act" level (action needed within the lesson).
For CO₂:
- Watch: 1,200 ppm during a lesson. Open a window mid-lesson.
- Act: 1,800 ppm sustained. Open all windows, brief pause.
For PM2.5:
- Watch: 25 µg/m³ during break. Investigate (cleaning chemistry, outdoor event).
- Act: 50 µg/m³ sustained. Run HEPA purifier, check outdoor air quality forecast.
For temperature:
- Watch: below 17 °C or above 23 °C. Check heating system.
- Act: below 16 °C or above 25 °C. Move class if necessary, log for SBM.
What to put on the dashboard.
Senior leadership want one screen: rooms in red / rooms in amber / rooms in green. Click through to per-room detail. Monthly summary email to the SBM and the headteacher; quarterly governor report.
Tenant-safe links (no audio data, no minute-by-minute) for parents who ask.