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March 2022

Why schools need clean air indoors

Written by Nathalie Leblond
Air Quality

Schools need good indoor air quality for many reasons, not least amongst them including learners' academic performance. Learn more about why clean indoor air is so essential for the education sector in our latest blog post.

Children the world over have had a hard time over the last two years. They've been put under enormous pressure during lockdowns, with most having to work from home and trying to keep up with their studies in isolation from their teachers and fellow students.

By the time many schools re-opened, the Covid-19 prevention mechanisms had shifted from emphasising surface hygiene and regular deep cleaning - to air hygiene. Numerous aerosol, engineering, atmospheric, and respiratory disease specialists presented evidence in a wide variety of studies that Covid-19 is primarily an airborne disease. This highlighted the importance of mask wearing and ensuring good indoor air quality to reduce the risk of infection.

Recent research (Dec 2021) by the Swiss Federal Laboratories for Materials Science and Technology (EMPA) has shown a clear link between poor ventilation in classrooms and high numbers of infections. This shows poorly ventilated classrooms (measured by CO2 sensors) had six times the number of cases of Covid-19.

The issue of keeping children safe from infection when schools opened up also highlighted a problem that has affected schools in many countries. Poor air quality in school classrooms has been impacting children’s learning for decades. This is despite large amounts of research that show that poor ventilation and pollution - both of which are highly prevalent in and around urban schools -  have major effects on children and educators' health, performance, and wellbeing. 

The Lancet COVID-19 Commission Task Force on Safe Work, Safe School, and Safe Travel noted that a review of air quality in schools in 13 countries found poor ventilation was common. Funds are being provided in many countries for schools to take measures to stay open safely.

The Lancet report highlighted that this provides a once-in-a-generation opportunity to make health-based improvements to school buildings, including indoor air quality. Preventing the spread of airborne diseases and reducing pollution in schools are part of the same problem.

Improvements in indoor air quality will both reduce the risk of children and staff catching airborne diseases and also reduce indoor air pollution, which will provide the benefits of improved health and academic performance. 

Why classroom air quality is important for children

Children in a classroom enjoying the low levels of indoor air pollution

It is widely recognised that some people are hypersensitive to low levels of indoor air pollution - or sick building syndrome (SBS). The specific causes of SBS have still not been fully clarified by research, but are thought to be caused by exposure to low levels of multiple pollutants, which makes it even more important to keep pollutant levels as low as possible. 

Schools in towns and cities are subject to high levels of outdoor air pollution too. A study by the London local government found that 98% of schools in London were in areas exceeding WHO pollution limits for PM2.5, the more damaging size of particulates, compared to 24% outside London, and we discussed the shocking state of South African air quality in one of our previous blogs; 5 shocking facts about air quality in South Africa

Unicef UK estimated in 2018 that one in three children were growing up in areas with high levels of particulates, totalling 4.5 million children in towns and cities. This is repeated in many towns and cities around the world with high levels of traffic and industry.

Poor indoor air quality is caused by numerous pollutants coming from both outdoor and indoor sources. These include volatile organic compounds (VOCs)  particulate matter (PM1.0, PM2.5, PM10), fungi (including mould spores), bacteria and viruses (carried in dust and respiratory aerosols), and even human skin particles. Vehicles congregate - often with engines running - in front of school buildings at certain times of the day, and schools also use many types of products in teaching, such as art and science materials, that are sources of pollution.

Children are particularly vulnerable to air pollution because their bodies are still developing. Younger children, especially, have an underdeveloped or compromised immune system. While children are still growing, their lungs are larger in proportion to their body size. Children also breathe more rapidly than adults so relative to their blood volume and body size their intake of toxins is greater and they absorb a greater concentration of pollutants.

There is a relationship between exposure to indoor pollutants and the development of respiratory symptoms and asthma among people who have not been sensitised before and those who are prone to allergies. Children are more likely to be susceptible while they are young and growing. Children who have been exposed to high levels of air pollution are also susceptible to chronic diseases later in life.

The effects of air quality on academic performance

The quality of the air in schools can have an impact on the children's health and wellbeing

Decades of research has shown that poor indoor air quality in schools has a variety of effects on children’s health, ability to learn, and academic performance. The wide ranging long-term health effects of pollution are well known and include lung diseases, cardiovascular disease, myocardial infarction, heart failure, neurological disorders, diabetes and cancer.

The effects of poor air quality are not always as obvious but include headache, fatigue, coughing, sneezing, dizziness, nausea, irritation of the eye, nose, throat, or skin. These have a direct effect on the academic performance of children and teachers and attendance at school.

The US EPA reviewed the scientific evidence on the impact of air quality on academic performance and classified studies according to their findings.

  • Higher outdoor ventilation (by HVAC or opening windows) in classrooms gave higher scores on standardized tests in math and reading.
  • Improved indoor air quality (IAQ), either by removal of pollution or higher ventilation rates, is linked to the faster and improved performance of children.
  • The poor physical condition of a building is linked to higher absenteeism and dropout rates.
  • A survey of teachers in two areas in the US found that the most frequently cited problem affecting teaching quality was poor IAQ.
  • Causes of pollution most frequently associated with respiratory problems such as asthma, include moisture damage, animal and biological allergens, NO2, moisture or dirt in HVAC systems, low ventilation rate, formaldehyde, cleaning products, outdoor pollutants and vehicle exhaust. In the US nearly one in thirteen children has asthma, which is the leading cause of school absenteeism caused by a chronic illness.
  • Higher ventilation rates reduce the transmission of infectious diseases and reduce rates of respiratory diseases.
  • Control of temperature and relative humidity to keep children in a comfort zone has the most positive impact on mental tasks requiring concentration.
  • Airborne or surface dust affects health in schools.

How can schools improve air quality?

Schools improving air quality for the health and academic performance of it's pupils

Schools have some unique considerations that can make managing air quality more difficult. A typical school can have four times as many people as office buildings per unit floor area, which will require higher rates of ventilation, and in many countries school budgets are under strain - with building maintenance often facing the largest cuts.

However, the pandemic has presented schools with a rare opportunity to solve the problem of chronic under ventilation and focus on improving indoor air quality. Many countries are now taking action by allocating significant budgets to improve indoor air quality.

There are several measures schools can take to improve indoor air quality.

  • Mechanical ventilation with an HVAC system. Often these have not been designed to have sufficient ventilation or filtration rates for airborne diseases and may need “topping up” by using portable air purification systems in classrooms. They also need to be maintained to perform adequately.
  • Natural ventilation, by opening windows where outdoor pollution levels are not going to negatively impact the air indoors and the outdoor air temperature difference won’t affect comfort indoors.
  • Portable air purification units that contain HEPA 13 filters. These filter particulates, including respiratory aerosols, and VOCs from the air (but not CO2, which will require ventilation). They should have a clean air delivery rate (CADR) to give a minimum of five air changes per hour (ACH) in the room.

Explore Initial's range of industry-leading air purifiers and take the first step in ensuring learner and educator safety. You can also download our brochure to find out more about the VIRUSKILLER™ range.


Nathalie Leblond

Nathalie Leblond

I joined Rentokil Initial South Africa in 2004 as the PA to the MD, and after 6 months maternity leave I re-joined the Company in 2009 as the Marketing Co-ordinator for Rentokil. I'm now the Marketing Communication Manager for Rentokil Initial. I'm still terrified of cockroaches (Americana's only!) but the rest of the creepy crawlies we deal with don't really bug me (see what I did there?), so I guess I'm in the right industry! I am passionate about what we do here at Rentokil Initial and also write for our Hygiene Blog, which can be found at blog.initial.co.za, and our Ambius blog - https://www.ambius.co.za/blog. Life outside of Rentokil Initial mostly revolves around my daughter, who has just turned twelve, and my husband (who is a bit older). I love living in Cape Town and wouldn't trade living here for anywhere else in the world.

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