Why is ventilation so important?
Ventilation is the process of replacing stale air with fresh air. Effective ventilation removes stale air which may contain Covid-19 aerosols and brings in fresh air containing more oxygen, less carbon dioxide (CO₂) and water vapour, and fewer microbes. Achieving good ventilation is all about understanding ventilation systems in the workplace (mechanical, natural, or both) and checking how well they are performing in removing stale air and bringing in fresh air. Our 5-step guide below sets out how employers and union reps can work together so that this can be achieved, including practical measures to monitor and improve ventilation.
Welsh Government guidance is clear about the importance of ventilation in relation to Covid-19. We welcome, as an initial step in the right direction, the announcement that the Welsh Government has heeded calls from the joint unions and has allocated funding for portable CO2 monitors for schools and colleges from September 2021. It is not clear how long the rollout will take so if schools and colleges are able to purchase a few of these devices this will help bridge the gap.
From September, despite high staff vaccination rates, staff are working alongside pupils of whom most will not be partly nor fully vaccinated. Masks and hygiene measures can help - but ventilation is key to a safer work environment. Good ventilation also aids student concentration, so will continue to pay dividends in relation to learning even when the pandemic is over.
- In New York City any room that does not meet stringent safety standards is not used for instructional purposes until it is put right. Air filters are being installed in every classroom.
- In Scotland, all schools must have access to CO2 monitoring and funding is being made available to local authorities to facilitate this.
- In Ireland, tens of thousands of CO2 monitors are being distributed to schools as part of a package of measures to help ensure safety.
A collective approach
Tackling poor ventilation collectively offers the best chance of success. As a starting point, it is essential that all colleagues understand why ventilation is so important. This short video from HSE explains why this is the case.
In order to ensure the importance of ventilation is understood and effective ventilation achieved, you should:
- Meet with members to discuss ventilation in the workplace.
- Identify any concerns and, where possible, solutions.
- Raise them collectively with your employer.
A joint approach to management, whether written or presented at a meeting, from members of all unions who are recognised at your workplace, setting out steps that you expect to be taken to protect everyone, is the best way forward. The key point is that negotiation between unions and management takes place. Most employers will welcome such a collaborative approach, since improving ventilation should lead to less Covid-19 transmission and therefore less disruption to education.
A step-by-step plan for assessing ventilation levels and bringing about any improvements needed is suggested below. If management is reluctant to engage, go back to members, discuss the position, and agree a plan. Members may wish to demonstrate how strongly they feel by signing a letter or raising it with the governing body.
Step 1 - Gathering evidence of poor ventilation
Union members/reps/health and safety reps can help draw attention to areas which need improving:
- Do any areas feel stuffy or smell unpleasant?
- Are there any areas of the premises without either natural ventilation, e.g., openable windows and doors or mechanical ventilation, e.g., fans and ducts?
- Are any airbricks blocked?
- Are there any windows which require attention?
- Do ventilation grids appear dirty?
- Are ventilation facilities blocked by furniture or curtains?
These are all indicators of poor ventilation. Feed any concerns through to management.
Step 2 – Workplace ventilation audit
The risk of transmission of Covid-19 from aerosols, and the ventilation strategy needed to reduce the risk, should be considered as part of your workplace’s overall risk assessment for Covid-19.
- Ask your employer to undertake a ventilation risk assessment to identify any poorly ventilated areas, including areas such as toilets.
- If there already is one, ask for a copy to be displayed on the staff noticeboard.
- Will it be revised at regular intervals?
Here are some key questions to ask your employer, which should be considered as part of the risk assessment process. Individual classroom or workspace occupants should be involved too.
- Are there any classrooms and other areas where people gather and where there is neither mechanical ventilation, nor natural ventilation such as open windows, doors, or vents?
- If there are mechanical systems that provide outdoor air, temperature control, or both then does the system only recirculate air with no outdoor air supply? If so, the area is likely to be poorly ventilated and any Covid-19 in the air will just be moved around rather than removed.
- Are there any indoor areas with fewer than 6 air changes per hour?
If the answer to any of these questions is ‘yes’ or ‘we don't know', then improvements are needed.
Step 3 – Monitoring carbon dioxide (CO2) levels
Many countries have now recognised the need to improve ventilation in educational buildings. Ireland is investing €4m to ensure that classrooms have CO2 monitors. Chile has repurposed CO2 monitors to stop Covid spread indoors. Data on CO2 is uploaded to the cloud and an audio alert. Germany announced (October 2020) a €500m investment to improve ventilation in public buildings including schools and Belgium is imposing requirements. In response to pressure from the education unions, Welsh Government is providing £2.58m for over 30,000 CO2 ‘traffic light’ monitors, for teaching and learning spaces such as classrooms, seminar rooms or lecture halls. These will be purchased by Welsh Government and rolled out to schools via local authorities.
The level of CO2 acts as a proxy for the Covid risk as people exhale airborne viruses when they exhale CO2. To check the situation in your workplace, ask your school or college to use carbon dioxide monitors to check whether ventilation is sufficient to keep CO2 levels below 800 parts per million (ppm). Indoor air with carbon dioxide levels at 600 to 800 ppm indicates a relatively well-ventilated room.
Please note carbon dioxide monitors are not a solution to the problem of poor ventilation. They will indicate a problem but then something must be done. More on this below.
In its advice Identifying poorly ventilated areas the HSE states that classrooms, meeting rooms and larger offices are often well suited to CO2 monitoring as the higher number of occupants helps ensure that measurements are accurate. It also advises that ‘where there is continuous talking or singing, or high levels of physical activity (such as dancing, playing sport or exercising), providing ventilation sufficient to keep CO2 levels below 800ppm is recommended.’
There are many different types of CO2 monitors available. For independent schools which will need to purchase their own, or where schools/colleges wish to purchase additional devices, the HSE advises that the most appropriate devices to use in the workplace are portable, non-dispersive infrared (NDIR) CO2 monitors. Detailed HSE guidance is available here.
Step 4 – Practical steps to ensure good ventilation
Where ventilation needs to be improved, here are some practical steps which can be taken, depending on what the specific issue is.
The maintenance team should check that the ventilation is functioning well, whether mechanical or natural. Schools and colleges with complex ventilation systems, may need to seek input from a qualified engineer and those containing asbestos from an asbestos consultant who can advise on the potential risk of asbestos disturbance in those areas.
- Airbricks should not be obstructed.
- Windows should be able to be safely opened.
- Ventilation grids need to be kept clean, so that the air supply is not obstructed.
- A minimum of six air changes per hour and a minimum of 10 litres per second per person of outside air are recommended.
- Where mechanical ventilation systems are in place, ventilation should start ahead of the working day and continue after classes have finished as cleaners and other maintenance staff will be working in those rooms. Where natural ventilation is relied upon, windows should be opened ahead of the start of the working day.
- Air handling units should be set to maximise outdoor air over recirculated air.
- Windows and internal/external doors should, where possible, be kept at least slightly open (noise, security/thermal comfort and fire restrictions dependent).
- To achieve a balance between ventilation and thermal comfort, uniform and dress codes should be relaxed in colder weather to allow staff and students to dress more warmly but, in addition, schools and colleges should, where necessary, have the heating turned up higher and for longer, starting earlier in the morning, to keep the temperature comfortable throughout the working day.
- Fan convector heaters can be used provided the area is well ventilated, but they should not be used in poorly ventilated areas.
- On hot, still days when there is little or no breeze, a fan can be positioned next to an open window to draw in the fresh air from outside and circulate it around the room.
- Classrooms and other areas should be ventilated properly between different classes and uses, including at breaks and at lunchtime. This is one of the most important measures to ensure effective ventilation and involves opening windows fully for a short period of time. Subjecting rooms to periods of no occupancy also allows contaminants to dissipate.
- Rooms should be cleaned regularly to reduce recirculation of any virus deposited on surfaces and absorbed on dust. Welsh Government is currently reviewing the effectiveness of Ozone machines, to aid ventilation in schools and colleges.
- Any ventilation is better than none, so, where possible, keeping the windows open a crack will help to reduce the concentration of any virus in the air. Lower temperatures and likely windier conditions in the winter months will increase the natural ventilation through openings. This means that partially opening windows and doors can still provide adequate ventilation at the same time as maintaining a comfortable temperature.
- Ventilation facilities should not be obstructed or blocked by curtains or furniture.
- Ceiling fans or desk fans can be used to prevent pockets of stagnant air, provided good external ventilation is maintained. They should not be used in areas of poor ventilation.
- A maximum capacity should be introduced for smaller rooms to ensure greater dilution – this may mean reducing numbers of students in smaller classrooms. Note that halving occupancy is equivalent to doubling the ventilation rate.
- Some poorly ventilated areas of the premises may need to be restricted to single occupancy, or very short durations, or put out of use until ventilation is improved.
- As well as through ventilation, the risk of aerosol transmission can be reduced by limiting activities that have been shown to increase aerosol generation, such as aerobic exercise and singing, so such high aerosol-generating activities may need to be limited in smaller and less well-ventilated classrooms.
Once changes have been made, maintenance staff should monitor again, and regularly thereafter, using CO2 monitors, to ensure good ventilation is maintained.
Step 5 - What if these measures are put in place but ventilation is still poor?
Air cleaning and filtration units are an effective means of reducing airborne transmission of aerosols where it is not possible to maintain adequate ventilation.
The HSE advises that these units are not a ‘substitute’ for ventilation. They can, however, play an important role where ventilation has not proven sufficient.
The HSE advises that the most suitable types to use are:
- high-efficiency filters - High Efficiency Particulate Air (HEPA) filters are no less than 99.97% efficient at capturing human-generated viral particles associated with SARS-CoV-2 (Covid-19) according to the Centres for Disease Control and Prevention; Ventilation in Buildings; update 2 June 2021
- ultraviolet-based devices
Any unit should be appropriate for the size of the area in which it is used, to ensure it works effectively. Professional advice should be sought to ensure the most suitable equipment is purchased.
Any areas identified as having unsafe levels of ventilation should be taken out of use pending improvements. Remember good ventilation doesn’t mean that other Covid-19 controls, such as face coverings and a focus on hygiene can be fogotton!