Solutions – Clean Air for Kids

What is Ventilation?

Proper ventilation is essential for comfort, health and safety. It helps remove pollutants, moisture and odours whilst ensuring an adequate oxygen supply.

Ventilation is the process of supplying outdoor air to a room and removing stale air from that enclosed space, to maintain good air quality.

It can occur naturally – through windows, vents or gaps

Or mechanically – using fans or mechanically ventilated systems

90% of UK schools are naturally ventilated, but with densely packed classrooms, opening windows is not enough on its own. Air filtration must be added to classrooms and school halls to achieve good air quality.

All About CO₂

Airborne diseases spread much better inside than outside; where people share the air in enclosed spaces. When an infected person breathes out CO₂, 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 infections spreading.

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.

Why do we measure CO₂?

Carbon Dioxide (CO₂) monitors tell us about how much of the air we are breathing in, has been breathed out by others.

When we exhale, we release air with a higher concentration of CO₂ that we inhale. Outdoors, this excess CO₂ quickly disperses into the atmosphere. However in indoor spaces, where air is more confined, CO₂ levels gradually rise the longer the room is occupied. The effect is amplified in crowded spaces, as each person adds more CO₂ to the air.

What should the CO₂ be in an indoor space?

The CO₂ concentration is measured in parts per million (ppm). The CO₂ level outdoors is approximately 420ppm. 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 inadequate ventilation, this level is almost impossible to achieve.

How can we measure CO₂?

Compact, portable monitors are available which reliably measure CO₂ in the air.

Some of them can log the data, so it’s possible to review what happens to the CO₂ levels across the day. Rather than just on-the-spot monitoring. Logging the data is essential for demonstrating that the CO₂ in a classroom is not safe.

The best type for measuring CO₂ are those with a NDIR (Non-Dispersive Infrared) sensor. This works by detecting how much infrared (IR) light is absorbed by CO₂ molecules and they display the result in ppm (parts per million).

For example:

0.042% CO₂ in the atmosphere = 420ppm

0.1% CO₂ indoors = 1000ppm

0.5% CO₂ indoors = 5000ppm

1% CO₂ indoors = 10,000ppm

What is Air Filtration?

Filtration is the process of removing airborne particles from the air. It traps particles such as dust, pollen, viruses, bacteria, smoke and other pollutants such as fungal or mould spores.

Air filtration is commonly used in mechanically ventilated systems but also as stand-alone portable plug-in filter to improve air quality and protect respiratory health.

Air filters can significantly increase the clean air supply in a classroom and therefore can be considered a cost-effective measure.

How are Air Filters Used?

Crucially, the school staff need to be engaged in managing the filters. They must be running continuously throughout the day; switched on at 8.30am and off at 5pm around one hour after the room has been vacated. There is no need for them to be left on overnight in an empty room.

How Should I Choose an Air Filter?

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. 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 Much Does a Filter Cost?

A rough calculation of the cost for a two-class entry primary school is approximately £5000.00, 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.

How do Air Filters Work?

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 the room is pulled in through the high-grade filter. This will trap 99.97% of the airborne contaminants that are present. The filtered, cleaner air blows out of the top of the fan back into the indoor space.

“Portable air filters – they’re cheap, easy, we know they clean the air… We need to know where to put them to get the best effect”

Professor Clive Beggs, UK Covid Inquiry. September 2024

What Can We Do to Improve Air Quality in Schools?

The Problem with School Buildings

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 Right Now?

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.