What practical measures can schools and colleges take to ensure, so far as reasonably practicable, that work areas are both well ventilated and comfortable to work in during the autumn and winter?
Government guidance is very clear about the importance of ventilation as part of safety measures in relation to Covid-19. “SARS-CoV-2 (Covid-19) is primarily transmitted between people through respiratory (droplet and aerosol) and contact routes. Transmission risk is highest where people are in close proximity (within 2 metres). Airborne transmission can occur in health and care settings in which procedures or support treatments that generate aerosols are performed. Airborne transmission may also occur in poorly ventilated indoor spaces, particularly if individuals are in the same room together for an extended period of time.”
And, with the possibility of symptomless carriers, there is really no way of knowing just how many people could be spreading it around a room. Bringing in outside air helps dilute any aerosols in a room that may contain the virus.
During the winter months, staff and students will be spending more time indoors. Ventilating indoor work areas, whilst at the same time ensuring a comfortable working temperature, will become more and more challenging. (Sixteen degrees C is the legal minimum workplace temperature but the NEU has always argued for a minimum of 18 degrees C based on previous standards for schools).
There is very little guidance for schools and colleges on this topic. The NEU has been pressing the Government to provide practical guidance about how to safely achieve this balance but so far nothing has been published. There is now some good general workplace guidance on ventilation from the Health and Safety Executive (HSE), and the following practical suggestions from the NEU draw upon the HSE advice as well as guidance from the Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA); also the CIBSE Covid 19 Ventilation guidance, CIBSE - Emerging from Lockdown.
The guidance identifies the need to optimise the amount of fresh air entering a classroom, balancing this with thermal comfort and the risks associated with open windows. The guidance recognises that it is challenging to secure enough ventilation, particularly in most schools/colleges which rely on natural ventilation.
The NEU view is that in order to help with the balance between ventilation and warmth, uniform and dress codes should be relaxed 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.
Balancing ventilation with keeping warm
Providing adequate ventilation does not have to mean that schools and colleges have to be cold. Good ventilation is about maintaining a balance between making sure workplaces are warm whilst keeping a flow of air going through an area.
Simple steps, such as partially opening windows, can be taken to ensure ventilation is maintained. Natural ventilation can be used with heating systems to maintain a reasonable temperature in the workplace.
If there are any existing issues with the functioning of the heating system, these need to be addressed as soon as possible since any breakdowns will make it even more difficult to maintain ventilation and a comfortable working environment.
Fan convector heaters can be used provided the area is well ventilated, but they should not be used in poorly ventilated areas.
Locating poorly ventilated areas
- Look for areas where there is no mechanical or natural ventilation, such as opening windows or vents. Mechanical systems should provide outdoor air and not be recirculating air only.
- Are there any areas that feel stuffy or smell badly?
- Use carbon dioxide (CO2) monitors to help locate areas of poor ventilation (see later in this briefing for more information).
Practical suggestions for ensuring adequate ventilation
- Please note: HSE’s published guidance on Ventilation and air conditioning during the coronavirus pandemic sets out steps that can be taken by schools without necessarily requiring access to specialist engineering advice. However, where a school has complex ventilation systems, then it may be appropriate to seek input from a qualified engineer.
- The maintenance team should check ventilation is functioning well. Airbricks should not be obstructed. Windows must be able to be safely opened. Ventilations grids need to be kept clean, so that the air supply is not obstructed. Any mechanical ventilation systems should be checked for their efficient functioning by the maintenance company.
- Start ventilation ahead of the school/college day and allow it to continue after classes have finished as cleaners and other maintenance staff will be working in those rooms.
- Set air handling units to maximise outdoor air over recirculation (see section below on mechanical ventilation).
- Open windows and internal/external doors as necessary (noise, security and fire restrictions dependent).
- Ventilate classrooms and other areas properly between classes and uses, including at breaks and at lunchtime. This is one of the most important measures to ensure effective ventilation and would involve opening windows fully for a short period of time.
- Any ventilation at other times is better than none, so keeping the windows open a crack will help to reduce the concentration of any virus in the air. Lower temperatures and likely windy 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.
- A minimum of six air changes per hour and a minimum of 10 litres per second per person of outside air are recommended.
- Staff should be instructed how to achieve the most effective ventilation – eg: opening top windows and moving obstructions such as curtains/blinds.
- Make sure that ventilation facilities are not obstructed or blocked by curtains or furniture.
- Use ceiling fans or desk fans to prevent pockets of stagnant air, provided good and external ventilation is maintained. They should not be used in areas of poor ventilation.
- Introduce a target maximum capacity for smaller rooms to ensure greater dilution – this may mean reducing numbers of students in smaller classrooms.
- Some poorly ventilated areas of the premises may need to be restricted to single occupancy or very short durations.
- Where poorly ventilated spaces cannot be adapted to improve ventilation, they should not be used as a teaching location.
- 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, singing and talking loudly, so such high aerosol-generating activities may need to be limited in smaller and less well-ventilated classrooms.
Schools and colleges should consider the installation of CO2 monitors. In teaching and learning spaces, carbon dioxide is taken to be the key indicator of ventilation performance for the control of indoor air quality. A CO2 monitor, with traffic light indications, sited away from windows, can be used to show a precise reading of the CO2 level in a room to identify where there may be challenges in ensuring adequate ventilation.
Carbon dioxide levels in a relatively well-ventilated room should be at 600 – 800 parts per million (ppm). Over 1,500 ppm indicates very poor ventilation and action is needed. Guidance from the Chartered Institute of Building Services Engineers (CIBSE) states that spaces with low occupancy or where enhanced aerosol generation is likely (e.g. through singing, loud speech, aerobic activity – all of which are likely in schools and colleges) should aim to ensure ventilation is sufficient to maintain CO2 concentrations below 800ppm (typically 10-15 l/s/person). Given issues around singing, we would particularly recommend that music rooms are checked with CO2 monitors.
Where these concentrations are being exceeded action should be taken, whether opening a window/more windows, using HEPA air cleaners or reducing the number of people in the room. Where CO2 monitors are installed in classrooms, staff can assist by keeping an eye on them, as can pupils. Moving the sensor around the school to check each classroom should give an indication of any areas where ventilation may need to be increased.
Portable HEPA (high efficiency particulate air filter) air cleaners based are another option. They are basically a box with a fan that draws air through a high efficiency filter. The filter removes nearly all virus relevant aerosols. HEPA air cleaners need to be of the right size for the room. They should be considered as part of the risk assessment, particularly where other measures aren’t possible or aren’t working.
Mechanical ventilation conveys fresh air into a building and can include air conditioning and/or heating. Systems that provide both air conditioning and heating are known as heating and ventilation air conditioning (HVAC).
To help reduce the risk:
- continue using most types of mechanical ventilation as normal and set them to maximise fresh air and minimise recirculation
- consider extending the operating times of HVAC systems to before and after people use work areas
- ensure mechanical systems are maintained in line with manufacturers’ instructions
Mechanical systems supplying individual rooms where recirculation modes allow higher rates of fresh air supply to be provided to an area should be permitted to operate.
If a centralised ventilation system that circulates air to different rooms is used, recirculation should be turned off and a fresh air supply used.
Recirculation units for heating and cooling that do not draw in a supply of fresh air can continue to operate provided there is a supply of outdoor air, for example windows and doors left open.
Recirculation units (including air conditioning) can mask poor ventilation as they simply make an area more comfortable.
Action points for reps/health and safety reps
- Check whether the risk assessment has been updated to address the issue of ventilation during the winter months and where necessary suggest the introduction of some of the measures listed above. The individual risks to staff who are more medically vulnerable need to be re-assessed too.
- Check the position of medically vulnerable staff. Those most at risk are the clinically extremely vulnerable (CEV) followed by the clinically vulnerable (CV). The NEU urges schools and colleges to permit those who are clinically extremely vulnerable to work from home, and in areas of intervention, allow those who are clinically vulnerable. To do so as well where risk assessments suggest this is appropriate. Where these staff are in school/college, it is imperative that they do not spend extended periods of time in poorly ventilated classrooms.
- Identify any rooms which present a greater hazard either because they are smaller but contain the same number of pupils as larger classrooms, or because there are other factors preventing ventilation, and seek to agree that these are only used by smaller groups, or not at all.
- Urge that CO2 monitors are made available so that measurements can be taken in all working areas. Where necessary, further action should then be taken to increase the flow of outdoor air into the space or bring in HEPA air cleaners.