Indoor air quality regulations UK
Indoor air quality regulations in the UK
The UK does not yet set a single legally enforceable indoor air quality limit for non-industrial workplaces. Instead, several pieces of legislation, standards and recognised guidelines together define what 'reasonable' IAQ looks like. This page summarises the main references and shows where independent monitoring provides supporting evidence — it is practical guidance, not legal advice.
Key references
What sits behind UK indoor air quality expectations
Different references cover different parameters and building types. A monitoring programme is usually aligned to the references most relevant to the asset.
Duty of care
General employer duty to provide a safe place of work.
1992
Effective ventilation of enclosed workplaces.
Ventilation
Design criteria for indoor environmental input parameters.
Health & wellbeing
Industry guidance on IAQ in non-domestic buildings.
Workplace duties
The Health and Safety at Work etc. Act 1974 and the Workplace (Health, Safety and Welfare) Regulations 1992 require effective ventilation and a healthy working environment.
Ventilation standards
BS EN 16798-1 and CIBSE TM40 set the fresh-air rates and IAQ categories most UK consulting engineers design and assess against.
Pollutant guidelines
WHO 2021 air quality guidelines and UK Air Quality Strategy values inform the thresholds reports compare measured PM2.5, NO₂ and ozone against.
Schools & healthcare
DfE BB 101 (schools) and HTM 03-01 (healthcare ventilation) add sector-specific expectations that monitoring can support.
When monitoring helps
Using monitoring to evidence compliance
Monitoring does not change the regulations — it demonstrates how the building actually performs against them. Programmes typically combine continuous CO₂ and particulate data with periodic testing of pollutants such as VOCs and formaldehyde.
Often paired with indoor air quality monitoring, office ventilation monitoring and healthy indoor environments programmes.
Benchmarks
Common reference values used in UK IAQ reporting
| Parameter | Typical reference | Source |
|---|---|---|
| CO₂ | < ~1000 ppm (offices, occupied) | CIBSE TM40 / BS EN 16798-1 |
| Fresh air per person | ≥ 10 L/s (typical offices) | BS EN 16798-1 / CIBSE Guide A |
| PM2.5 (24-h) | < 15 µg/m³ | WHO 2021 |
| NO₂ (annual) | < 10 µg/m³ | WHO 2021 |
| Formaldehyde (30-min) | < 100 µg/m³ | WHO IAQ guideline |
| TVOC | < 500 µg/m³ | WELL v2 Air (reference) |
Evidence IAQ performance against UK guidance
Independent monitoring aligned to BS EN 16798-1, CIBSE TM40 and WHO 2021 — with a written report that maps results to recognised reference values.
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Specific parameters