The importance of ventilation
The importance of air filtration

The importance of ventilation

Ventilation is essential in all enclosed workplaces, as it brings in fresh air and removes carbon dioxide from the room, which has been proven to affect pupils’ ability to learn in high concentrations.

It also removes other pollutants and allergens, as well as pathogens that transmit infectious diseases.

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’.

Not only is it the law to provide sufficient fresh air, but studies have shown that good ventilation is associated with:

• improved health;

• better concentration;

• higher levels of satisfaction with an environment;

• lower rates of absence from work;

• better quality of sleep; and

• reduced exposure to a wide range of air pollutants.

Ventilation improves the air quality in rooms, improves comfort levels and decreases the levels of any pathogens and allergens. With regard to pathogens such as cold, flu or Covid-19 viruses, adequate ventilation reduces the levels of viruses in the air. It helps reduce the risk from aerosol transmission, when someone breathes in small particles (aerosols) in the air after a person with a virus has been in the same enclosed area.

The risk of transmission of viruses is greater in areas that are poorly ventilated.

Poorly ventilated areas will normally be hotter and stuffier than areas with good ventilation, and will have higher levels of carbon dioxide (CO₂).

Adequate ventilation is not just a health and safety issue, but is also a teaching and learning issue. There is a scientifically proven link between levels of CO2 and the brain’s ability to learn. Adequate ventilation is therefore vital for effective learning to take place.

Identifying poorly ventilated areas is very important and can be done using carbon dioxide (CO₂) monitors, which were distributed during the Covid-19 pandemic and should still be in use.

Where CO₂ levels rise above 800ppm occasionally, this should be viewed as a sign that ventilation needs to be increased. This is usually achieved by opening doors or windows.

Whilst opening doors can be effective, internal fire doors must not be propped or wedged open unless fitted with automatic closing devices. External fire exit doors can be opened and propped or wedged open, provided they open into a secure location and do not pose a safeguarding risk.

Where a room has levels consistently above 800ppm, this should be reported to school management, as if normal opening of windows etc. is not effective, other measures such as mechanical ventilation, limiting the numbers of people in the room, or repairing windows that no longer open will need to be considered.

Where levels exceed 1500ppm, this is indicative of poor air quality and the air in the room should be purged. School management should be informed if levels cannot be lowered sufficiently, as additional measures such as detailed above may be required. If the levels cannot be quickly lowered to acceptable levels, school management should be informed and an alternative room should be provided. The room should also have an additional risk assessment carried out. HSE guidance on the use of CO₂ monitors and their placement can be found on the HSE website.

Irrespective of the availability of CO₂ monitors, rooms without sufficient natural/mechanical ventilation, where there is a feeling of ‘stuffiness’ or bad odours, or where there are any other concerns about ventilation will require measures to be taken.

Further guidance on ventilation is available on the HSE Ventilation in the workplace web page.

Where ventilation is poor, air filtration units are to be used to purify the air, although these will not reduce CO₂ levels.

Where there are concerns about ventilations, members and NASUWT Representatives should raise these with management in the first instance. If the response in insufficient, you should contact NASUWT for further advice.

The importance of air filtration

Achieving sufficient ventilation can present challenges in some rooms, especially in winter, where a balance with thermal comfort is required.

In addition, many pupils and staff have conditions such as asthma and hayfever made worse by airborne allergens and contaminants, that ventilation alone may not be sufficient to mitigate. This is particularly true with pollen.

Air quality in schools and colleges in areas of high air pollution may also find ventilation from outside air introduces pollution, rather than reduces it.

There is also clear evidence that the installation of air filtration units leads to improved educational outcomes, including:

• Air Filters, Pollution, and Student Achievement, New York University

• The long run economic consequences of high-stakes examinations: evidence from transitory variation in pollution, London School of Economics

• Addressing Education and Health Inequity: Perspectives from the North of England, Child of the North All-Party Parliamentary Group (Page 27)

• The cleaner the air, the better they fare: The effects of air filtration on student achievement. IZA Institute of Labor Economics

Portable, plug-in and used air filtration units typically use high efficiency particulate air (HEPA) filters to remove microscopic particles from the air. This will include viruses and other pathogens as well as allergens and pollutants.

Some also employ ultraviolet (UV) light to kill pathogens, but this is not proven to be necessary or to be effective in portable HEPA units. UV may, however, be useful inside mechanical ventilation systems and professionally installed upper room UV C Germicidal Irradiation systems.

HEPA filters are a long-used and proven technology removing all types of airborne particles, guaranteed to remove 99% of 0.3 micron particles, and have been proven to effectively remove aerosols containing virus particles from the air.

In one study at Addenbrookes Hospital in Cambridgeshire, virus levels in the air of a ward treating Covid-19 patients were reduced to undetectable levels when HEPA filters were employed.

HEPA filtration systems clean the air without adding dangerous chemicals to the air that other devices, such as ionisers and ozonisers do. These types of purifiers should be avoided.

It is likely that a filter would pay for itself very quickly by reducing absence rates, as well as improving learning.

Choosing a filtration unit

There are two considerations to take into account when considering a filtration unit and schools should have competent advice to assist:

• the clean air delivery rate (CADR) - how much air is filtered per hour;

• the noise level of the unit - some are much louder than others. Forty-five dB and below should be the aim.

The noise levels and CADR should be stated on the product.

The CADR required depends on the size of the room and the number of people within the room. Filtration units should be purchased on the basis of maximum occupancy.

A good yardstick to use is five litres of filtered air per person per second, which equates to 18m3 per person per hour. If the room has a maximum occupancy of 32 people, that would be a CADR requirement of 576m3 per hour.

It can be more useful to buy two smaller units rather than one large one as this allows the filtration to be adjusted by the occupancy, spreads the filtration around the room and can reduce noise level.

Imperial University have also provided a free to use web tool called CHEPA.

The CHEPA (Classroom HEPA) impact calculator is a tool which asks straightforward questions about a classroom, such as its floor area and height, the number and age of the pupils using it, and based on this information, makes a tailored calculation of the impact of adding an air filter unit on that classroom’s air quality and energy use.

 

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