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All employers have a duty to ensure there is adequate ventilation throughout the enclosed areas of their workplaces. The Health and Safety Executive (HSE) has recently published new guidance.

Ventilation is the process of replacing indoor air which may be stale, hot and humid or contain pollutants or impurities, with fresh air from outside. Employers must assess the workplace to identify any areas that are poorly ventilated, and then take appropriate action to improve ventilation.

This duty deals with providing sufficient fresh air under health and safety law, and is separate to that required under the Control of Substances Hazardous to Health Regulations (COSHH) and local exhaust ventilation, which both cover the removal of harmful airborne substances, such as fumes and dust generated by certain work processes.

Why is ventilation important in the workplace?

Under Regulation 6 of the Workplace Health, Safety and Welfare Regulations, employers must ‘ensure that every enclosed workplace is ventilated by a sufficient quantity of fresh or purified air'.

As well as being a legal requirement for employers to ensure their workplace has sufficient fresh air, studies also show that good ventilation and indoor air quality offers a range of benefits to employees. These include:

• Enhanced health
• Improved concentration
• Greater levels of satisfaction with an environment
• Reduced rates of absence
• Better sleep quality
• Reduced exposure to air pollutants

It is believed that poor ventilation or poorly maintained air conditioning systems, amongst other things, can lead to poor indoor air quality, which can cause ‘sick building syndrome'. This is the name given to symptoms that arise when time is spent in a particular building, and that subside on leaving.

Such symptoms may include headaches; blocked or runny nose; dry, itchy skin; dry, sore eyes or throat; coughing or wheezing; skin rashes, or tiredness and difficulty concentrating.

How to ventilate a workplace?

Workplace ventilation can either be natural, or mechanical. The chosen method will depend on the building, and the most appropriate options for your particular workplace.

Doors, windows, trickle vents, air bricks and grilles can all provide natural ventilation. Mechanical ventilation uses fans to move air in and out of rooms. Some workplaces will use a combination of natural and mechanical ventilation. Desk or ceiling fans are not considered suitable methods of mechanical ventilation as they do not improve fresh air and merely circulate the existing air in the same space.

A heating, ventilation and air conditioning (HVAC) system can be manually controlled, or smart controlled. Smart HVAC systems use a series of Internet of Things (IoT) connected sensors to monitor indoor air quality, feeding back data into a central platform where artificial intelligence triggers automated actions, making adjustments to achieve optimum working conditions.

It is often advisable to consult with a ventilation engineer who will provide expert advice on the most effective system for your particular workplace.

Ventilation risk assessments

All employers must carry out a workplace risk assessment, part of which should include identifying poorly ventilated work areas. Such areas may be those where there is no natural or mechanical ventilation, or zones that smell bad or feel stuffy. It may be necessary to use a carbon dioxide monitor to identify poor indoor air quality.

It is often helpful to create a floor plan to set out how individual areas are ventilated. Every area should be covered, including rest rooms and canteens.

Where ventilation issues are detected, steps will need to be taken to make improvements. These could be simple, for example opening vents, windows and doors (not fire doors). Alternatively, it may be necessary to install a mechanical ventilation system, on the advice of a ventilation engineer.

Any existing HVAC systems will need to be regularly serviced and adequately maintained to ensure they are operating efficiently, i.e. doing a sufficient job of providing fresh air consistently, and not wasting energy. It may be necessary to upgrade to a new system if it is not possible to make sufficient improvements to the existing one.

It is important to ensure that the air being brought in from outside is actually fresh. If it isn't, for example, if it is contaminated with pollutants, then it will need to be filtered.

If a building uses an air recirculation system, the air should be filtered so as to remove particulates. Fresh air will need to be added to it before it is reintroduced into the workplace. Air recirculation systems should not be used where COVID-19 or other airborne viruses or bacteria are assessed as a risk.

The HSE Approved Code of Practice states 'In the case of mechanical ventilation systems which recirculate air, including air-conditioning systems, recirculated air should be adequately filtered to remove impurities. To avoid air becoming unhealthy, purified air should have some fresh air added to it before being recirculated. Systems should therefore be designed with fresh-air inlets, which should be kept open.'

If the steps taken to improve workplace ventilation fail to improve indoor air quality, then it may be necessary to change how workspaces are actually used. For example, reducing how many people are using the space, or the length of time they spend in it.

Further information on workplace ventilation

The HSE website provides detailed information on workplace ventilation, including a real life example of how workplace ventilation was improved.

There is also a video providing basic advice on providing fresh air at work.