Ventilation and indoor air quality requirements

Your ventilation and air quality duties

Adequate ventilation is both a building regulations requirement and a workplace health and safety obligation. Two separate sets of regulations apply to most business premises, and you need to comply with both.

The Building Regulations 2010 (Approved Document F) set minimum ventilation rates for buildings, particularly when new buildings are constructed or existing ventilation systems are significantly modified. The Workplace (Health, Safety and Welfare) Regulations 1992 require all employers to provide effective and suitable ventilation in the workplace as an ongoing obligation.

Poor ventilation leads to a build-up of carbon dioxide, moisture, pollutants, and airborne contaminants. This causes discomfort, reduces productivity, and can lead to health problems including respiratory conditions and sick building syndrome. In extreme cases, inadequate ventilation of combustion appliances can cause carbon monoxide poisoning.

Workplace Regulations 1992: fresh air standards

The Workplace (Health, Safety and Welfare) Regulations 1992 set a general duty to provide effective and suitable ventilation with fresh or purified air in every enclosed workplace.

The HSE guidance recommends 5 to 8 litres per second of fresh air per occupant as a general standard. In practice, this means:

• Natural ventilation - openable windows, doors, and other openings should provide sufficient air movement. The area of openable windows should be at least one-twentieth of the floor area for adequate background ventilation.
• Mechanical ventilation - where natural ventilation is insufficient (for example, in internal rooms, basements, or high-occupancy spaces), mechanical ventilation must be provided. Systems should include a warning device to alert occupants if the system fails.
• Combined approach - many premises use a combination of natural and mechanical ventilation. The key test is whether air quality is adequate for the number of occupants and the activities carried out.

Temperature requirements

Closely linked to ventilation, workplace temperature is regulated under the same Workplace Regulations 1992.

These temperatures are HSE guidance figures rather than absolute legal limits. However, if temperatures consistently fall below the guidance minimums, this may indicate a ventilation or heating problem that needs addressing. There is no statutory maximum temperature, but you must carry out a risk assessment if workplace temperatures become uncomfortably high and take reasonable steps to keep temperatures at a comfortable level.

Practical measures for managing temperature include:

• Providing thermometers so workers can monitor conditions
• Adjusting heating and ventilation controls
• Providing fans, portable coolers, or additional heating as needed
• Allowing flexible clothing during extreme temperatures
• Providing cool or warm drinks

Part F ventilation requirements

When you construct a new building or significantly modify an existing ventilation system, Approved Document F of the Building Regulations sets detailed minimum ventilation rates.

Key requirements under the 2021 edition of Part F

The 2021 update to Approved Document F strengthened several requirements:

• CO2 monitoring - CO2 monitors are now required in offices and similar occupied spaces to verify that ventilation is adequate. A reading consistently above 1,000 ppm indicates insufficient ventilation.
• Trickle vents - background ventilation through trickle vents or equivalent is required in all habitable rooms. This is particularly important in well-sealed modern buildings where natural infiltration is minimal.
• Extract ventilation rates - kitchens, bathrooms, and utility rooms require specific extract rates (30 litres per second intermittent for kitchens, 15 litres per second for bathrooms).
• Mechanical ventilation with heat recovery (MVHR) - where MVHR systems are installed, they must achieve a minimum 70 percent heat recovery efficiency.

When do Part F requirements apply?

Part F requirements are triggered by building work. You need to comply when:

• Constructing a new building
• Carrying out a material change of use (for example, converting a warehouse to offices)
• Replacing or significantly modifying a ventilation system
• Replacing windows (trickle vent requirements apply to replacement windows)
• Carrying out renovation work that affects the building's air tightness

Routine maintenance of existing ventilation systems does not trigger Part F compliance, but the Workplace Regulations 1992 ventilation duties apply at all times.

Maintaining mechanical ventilation systems

If your premises have mechanical ventilation, regular maintenance is essential to ensure the system continues to provide adequate air quality:

• Filter replacement - replace or clean filters at intervals recommended by the manufacturer. Dirty filters reduce airflow and can harbour bacteria.
• Ductwork cleaning - inspect ductwork periodically for contamination, particularly in kitchen extract systems where grease accumulates.
• Fan maintenance - check fans for correct operation, unusual noise, and vibration. Worn bearings or loose mountings reduce efficiency.
• Controls - verify that time switches, sensors, and control systems are functioning correctly. Systems that run when not needed waste energy; systems that do not run when needed compromise air quality.
• Commissioning records - keep the original commissioning record showing measured airflow rates. This provides a baseline for checking whether the system is still performing as designed.