"Schools should be safe places of learning, not places where students are at risk of health hazards."
Dr Maria Neira, Director at the World Health Organisaton
Why is Indoor Air Quality Important?
Indoor Air Quality (IAQ) refers to how good the air is in our homes, schools, offices or other public spaces. Until recently, most people had not given the air that we breathe indoors much consideration. But it's an invisible risk and the US Environmental Protection Agency ranks it as one of the top five environmental dangers.
We spend 90% of our time inside buildings where the concentration of pollutants can be up to five times higher than outside. Members of our society who are most susceptible to the adverse effects of pollution - the very young, the elderly, people suffering from health conditions - spend even more time indoors.
Concentrations of some pollutants have increased in recent decades due to: energy-efficient building construction and increased use of synthetic building materials, furnishings, personal care products and household cleaners.
The effect of ventilation on disease transmission was recognised by Florence Nightingale in 1859 (during a tuberculosis epidemic) and buildings were designed with far better ventilation as a result. Over time, the focus on energy efficiency has seen many of those ventilation enhancements in old buildings removed and newer builds have not given it sufficient priority.
The COVID-19 pandemic has exposed the problem of ignoring indoor air quality, spurring a renewed focus on poor ventilation. The air quality in buildings is critical for minimising the spread of airborne infectious diseases and reducing the pollutants that trigger chronic illnesses.
Children are more vulnerable than adults to the adverse effects of poor air quality because their brains and bodies are still developing. However, research has shown simple interventions to improve IAQ in schools have the potential to improve children's health significantly.
What are Indoor Air Pollutants?
Fine Particulate Matter (PM2.5 and PM10) produced by vehicles, heavy industry and wood burning.
Nitrogen Dioxide (NO2) from coal-fired power plants and road traffic.
Viruses and Bacteria produced by people breathing; can linger in the air for hours in densely occupied spaces.
Volatile Organic Compounds (VOCs) present in building, furnishings, cleaning products, and art & craft materials.
Carbon Dioxide (CO2) produced by stoves and humans breathe out CO2. In poor ventilation, the CO2 can quickly build up.
Radon Gas is created when natural radioactive uranium decays in the ground under our buildings and seeps to the surface.
Dust powder-like particles including clothing fibres, pet hairs, soil and dust mites.
Pollen produced by plants and trees; it is a significant problem for asthma sufferers.
Mould Spores are caused by damp, poorly ventilated buildings.
Fungal Spores can be found in high concentration in urban areas and thrive in damp buildings.
What Can We Do to Improve Air Quality in Schools?
It is not always feasible to open classroom windows if they are broken, sealed shut or it's cold and windy outside. If a school is in an area of high air pollution, fresh air from outside is not possible. Getting CO₂ under 800ppm can be very difficult, especially as most UK state schools are reliant exclusively on windows. There is also the problem of heating energy being lost out of open windows during the winter season.
Many school buildings are generally in poor condition and require extensive refurbishment. This should include upgrades to mechanical ventilation with heat recovery (MVHR) systems. The schools in the UK are often old buildings and all unique; therefore every educational setting needs to be properly assessed by a ventilation engineer. This all requires substantial financial investment from the government and time to repair the buildings.
What can be done in the interim?
An immediate way to improve indoor air quality is to install portable air filters. They have low energy consumption, drawing a similar amount of power as a lightbulb. This means in winter it can provide a more energy-efficient strategy than opening windows wider, thereby saving money on heating bills. Filters will not reduce the CO₂ levels but will make the room safer to occupy. Extraction fans and ceiling fans can also assist ventilation.
So an air filter is an effective way to supplement ventilation. It will significantly reduce disease transmission risks, asthma triggers, other pollutants and consequently school absence.
Other strategies that have been considered in schools (such as ionization, plasma systems or UV) are considered less cost-effective or scientifically defensible due to their unproven efficacies and their potential for degrading the quality of the air through the generation of harmful secondary pollutants.
Why Does CO₂ Matter?
Airborne diseases spread much better inside than outside; where people share the air in enclosed spaces. When an infected person breathes out, they exhale microscopic particles laden with virus which can stay invisibly suspended in the air for hours. Good ventilation helps to remove these particles and reduce the risk of viruses and bacterial infections spreading.
Ventilation refers to replacing stale indoor air with outdoor air. This is either by opening windows and doors or via mechanical systems installed in the building. But how effectively are our indoor spaces being ventilated?
Carbon Dioxide (CO₂) monitors inform us about how much of the air we are breathing in, has been breathed out by others. The CO₂ concentration is measured in parts per million (ppm). The CO₂ level outdoors is approximately 415ppm. The aim is to get the indoor air as close as possible to the outdoor air.
The recommended threshold for the lowest risk indoors is to have CO₂ under 800ppm. Unfortunately with densely packed classrooms and often inadequate ventilation, this level is almost impossible to achieve.
The UK government spent £25million on supplying schools with CO₂ monitors but this initiative has been poorly run, with limited training available for educators and no facility for externally collecting the data from classrooms. The outcome is that air quality in schools is not routinely assessed; in reality CO₂ monitors are just not present in classrooms any longer.
*The graph on the left is an example of CO₂ levels in a UK classroom, during winter. When the pupils enter at 9am, the CO₂ immediately rises up beyond the recommended 800ppm and stays up above 2000ppm for the majority of the school day. It drops at 3.30pm because the monitor was removed from the classroom.
What is an Air Filter?
A portable air filter is a stand-alone unit that captures microscopic particles. It is a simple but effective concept that was designed in World War II to filter radiation. The filter panels are comprised of multi-layered mesh made of very fine polypropylene or fibre-glass threads. Using an in-built fan, the air circulating in a room is pulled through the high-grade filter to trap 99.97% of the airborne contaminants that are present.
They must be running continuously; switched on at 8.30am and off at 5pm approximately one hour after the room has been vacated, but there is no need for them to be left on overnight in an empty room.
Air filters can significantly increase the clean air supply in a classroom and therefore can be considered a cost-effective measure.
A rough calculation of the cost for a two-class entry primary school is £5000, which equates to around £10 per child per year. After that initial layout, in subsequent years the cost would be less because the school would only need funding for replacement filter panels.
It is critical to install a filter with the appropriate Clean Air Delivery Rate (CADR) otherwise the air will not be as safe as it should be. So it is important to get the right filter for the size of the space and potentially more than one machine. The World Health Organisation recommends SIX Air Changes Per Hour (ACH) of ventilation for schools.
Air Changes Per Hour means the number of times that the total air volume in a room or space is completely removed and replaced in an hour. But with air filtration, the air is not removed, it instead cleans the air that is already in the room. This is therefore called equivalent Air Changes Per Hour (eACH).
How to Choose an Air Filter
1. Calculate the classroom dimensions. Multiply height X width X length = the overall room volume.
2. Check the filter's CADR which is expressed in cubic feet per minute (CFM) or cubic metres per hour (m3/h).
3. Check the noise level of the filter on different settings. For classrooms, it is recommended to keep levels below 40-45 decibels.
4. Choose the number of filters appropriate to the educational space.
5. Remember to check how many plug sockets are available as this affects how many filters can be run.
For assistance in working out how many air filters your school rooms require, visit this helpful website:
The TAPAS (Tackling Air Pollution At Schools) network comprises stakeholders across academia, education, public policy, civil society and business. They work together to support the development of healthy schools by improving air quality.
TAPAS recommend introducing an accredited organisation to ensure objective assurance of safety and efficacy of devices, in realistic environments considering both biological and chemical pollutants.
Air Filtration is Effective
"We know [air filters] work, so use them where there are infection risks and ventilation is not sufficient."
Professor Catherine Noakes OBE, Environmental Engineering for Buildings at the University of Leeds
Research carried out at Addenbrooke's Hospital investigated how effective air filters could be. The study was led by a team of doctors, scientists and engineers from Addenbrooke's and the University of Cambridge in January 2021.
Air filters were placed on Covid wards and the air quality was analysed with the machines switched on for a week, off for a week and then on again for another week.
The team found that with the machines switched on, they removed all traces of airborne SARS-CoV-2.
Health Effects of Poor Indoor Air Quality
Air pollution can affect every organ in the body and impacts adversely on our climate. The World Health Organization estimates that poor indoor air quality accounts for an estimated 3.2million premature deaths every year. Particulate matter and other contaminants are capable of penetrating deep into the lungs and entering the bloodstream which then carries these pollutants around to vital organs and the brain.
This can cause symptoms and diseases including the following:
- Headaches, dizziness and fatigue
- Cognitive difficulties
- Irritation of the eyes and throat
- Lung inflammation
- Asthma
- Respiratory disease
- Heart attacks and strokes
- Neurological disorders
Benefits of Safer Air
We wouldn't let our children drink dirty water, why are we letting them breathe dirty air?
In addition to decreased infectious disease transmission, research shows that ventilation and air filtration lead to improved academic performance, fewer missed school days for students and higher scores on cognitive function tests. Also there are benefits for teachers including decreased respiratory symptoms, increased staff retention, and improved morale.
A recent study led by E3 Pandemic Response and conducted in Finland, demonstrated positive results. Air filters were placed in two daycare centres which led to a reduction in illnesses and absences among children and staff.
The initial results from the first year of research are promising, according to researcher Enni Sanmark, from HUS Helsinki University Hospital. "Children were clearly less sick in [these] daycare centres — down by around 30 percent" Sanmark explained.
"The air [filters] were changed at two daycare centres serving as a control in the experiment, in order to rule out the effect that possible epidemic fluctuations could have on the results. The study's next phase will continue until April. We will be able to analyse whether there were only decreases in flu-type illnesses or whether the use of air purification could also help reduce stomach ailments," Sanmark said.
"At the moment, we are cautiously positive. Daycares and schools [here] have not done this before, but of course results from around the world show that air purification can reduce pathogens in the air, so our results are in line with these findings. We're excited and will continue our research."
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