Maintaining a steady supply of fresh air has always been a critical occupational safety requirement, but helping your employees breathe easy is particularly important as we enter the next phase of the pandemic.
As COVID-19 restrictions relax and more staff return to site, it’s essential to provide appropriate ventilation levels within enclosed workspaces, alongside other safety measures such as face coverings, social distancing, frequent disinfection and good hand hygiene.
When an infected person breathes, talks or sneezes, they transmit contagious aerosols. These contaminated particles remain in the air and can be inhaled by others. The risk is far higher when indoors, even when people are socially distanced. Introducing fresh air into a space – either through open windows and doors, or via fans and ducts – helps fight transmission by dispersing viral droplets.
Take steps to cut airborne COVID-19 hazards with a summary of HSE guidance on ventilation and air conditioning safety.
Pinpoint poorly ventilated areas with a risk assessment
A risk assessment helps you locate poorly ventilated areas across your workplace and implement appropriate controls. When conducting your risk assessment, walk your site and use floor plans to map out the ventilation methods in each zone, including shared spaces like break areas, canteens and changing rooms.
The HSE advises employers to:
- Identify workspaces that have no mechanical or natural ventilation via windows, doors or vents.
- Ensure that mechanical systems provide an outdoor air supply, temperature control or both. If air is merely recirculated through the system, ventilation levels are likely to be inadequate.
- Make note of spaces that feel stuffy or smell bad.
- Consider using carbon dioxide monitors as an additional measure of ventilation quality.
- Share the outcome of your assessment with staff to help them understand their role in reducing COVID-19 transmission risks.
Key considerations for your risk assessment
Aerosol transmission is affected by a number of factors. The more people occupying a space and the longer they spend together, the higher the danger. Work activities that are physically demanding or require shouting to be heard over machine noise can also raise risk levels.
In addition to these considerations, an HSE-approved risk assessment should also cover:
- The size of the area – Large areas present a lesser risk because aerosols accumulate more slowly within the space.
- Features that impact ventilation – Sizeable machinery and equipment can obstruct the flow of air through an area.
- Desk or ceiling fans – These types of fans should not be used in poorly ventilated places.
- Local exhaust ventilation (LEV) – Ventilation is improved if your LEV system expels air outside.
- Complex ventilation systems – Older premises, buildings with different systems on each floor and certain manufacturing ventilation set-ups could require a specialist survey. Speak to a ventilation engineer or consult current guidance from the Chartered Institution of Building Services Engineers (CIBSE).
Tips on improving natural ventilation
Natural ventilation brings in fresh air through windows, air vents and doors. If you’ve located an area with poor ventilation, you can make improvements by:
- Ensuring all doors, windows and vents can be opened. Please note, you should never prop open a fire door.
- Keeping windows and doors partially open when people are using the space.
- Checking if trickle vents can be opened in colder temperatures.
- Frequently airing rooms by fully opening all doors and windows (ideally when the room is empty) to optimise air flow.
- Training your workers on the need to maintain good natural ventilation.
Tips on improving mechanical ventilation
Mechanical ventilation carries fresh air into your premises from the outside through vents or ducts. Ventilation rates should be based on an area’s standard occupancy and shouldn’t be altered if staff numbers change temporarily. You can optimise mechanical ventilation by:
- Understanding how your system works. Ask your service team how much air is provided, the method of supply and how the equipment is maintained.
- Checking if the system’s fresh air intake delivers adequate ventilation and boosting levels with natural air sources, if needed. Your settings should maximise fresh air and minimise recirculation.
- Extending your system’s operating times beyond core working hours.
- Preventing air from recirculating across different areas and masking ventilation issues. Air conditioning models that don’t draw in fresh air can be used if outdoor air is brought in through open windows and doors.
- Checking guidance on different ventilation systems from the Chartered Institution of Building Services Engineers (CIBSE).
A note on air cleaning and filtration units
Where it’s not possible to maintain adequate ventilation, local air cleaning and filtration units can be used to reduce aerosol transmission. However, these systems are not a substitute for ventilation and you should put improvement plans in place before using air cleaning equipment.
The HSE recommends high-efficiency filters or ultraviolet-based devices that are appropriate to the size of the space. Further HSE guidance is available here.
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