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Air Sentry Systems since 2000

Do air purifiers work?

The answer is yes, if they are designed and deployed correctly.

What are the critical elements in design and deployment?

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Do Air Purifiers work?

Firstly, let's understand what is in the air.

The air in your home and the air in hospitals is the same air.

It seems obvious to state that but it means that many of the things that create problems for patients in hospitals are also in the air in our homes, and vice versa. Dust mites and bed mites float around in unseen quantities that our minds do not wish to accept.

Moulds such as Aspergillus, that black mold we see on many surfaces, is everywhere. When we start to analyse airborne particles and just how many particles are in our air initially it seems unbelievable. 

"Air is essential for life and yet remains an overlooked mystery to many. Air is everywhere yet we allow it to become polluted with emissions and in health care even common sense precautions around infected patients, such as high end FFP3 masks, are decried as unnecessary expenses."

Dr Clive Beggs, ‘The Forgotten Pathway’. 2003 paper titled “The Airborne Transmission of Infection in Hospital Buildings: Fact or Fiction”.

What exactly is a HEPA filter?

In a nutshell, the higher the grade, the better the filter. So HEPA14 is better than HEPA10. 

Medical Air Purifier HEPA Filter

What many people do not realise is that HEPA filters are not all the same. Indeed there are a range of grades of high efficiency particulate air filters which are numbered ten through to fourteen but these are not the highest standard.

After HEPA there are the higher grades of ULPA (Ultra Low Particulate Air) numbered fifteen to seventeen and SULPA (Super Ultra Low Particulate Air) numbered eighteen and nineteen. To the lay person this can be very confusing indeed.

How clean is the air in a Clean Room?

Clean Room standards are required to manufacture food and critical electronics.

These start at EN ISO 14644 Level Nine. At this level it is acceptable to have over thirty-five million particles of 0.5µm side and over eight million at 1µm, per cubic meter, and that is in a clean room!

An office environment is often so much higher that standards look at the weight of the particles rather than the overall number. Our bodies are amazing. We breath these sorts of concentrations into our lungs with every breath and our immune systems analyse how many are problematic. It is only when we become ill or the concentrations overwhelm us that these airborne particles become problematic.

Do Air Scrubbers clean the air?

Understand the difference between an air scrubber and an air purifier:

The first thing to understand is that an air purifier or air filter is not necessarily an air scrubber. Even professional authorised engineers often make this error. An air scrubber removes a gas from the air, such as CO2, not particles.

It could be argued that a filter containing activated carbon filters is a form of air scrubber. This is because they remove gas, but the term is normally used for systems that contain a chemical, such as soda lime. The chemical is used to remove a specific gas or some specialised electrostatic type precipitators that can attract and then repel a gas, depending upon how they are charged.

Activated carbon filters are important though, because they remove many pollutant gases created by industry and our cars.

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How to remove particles from the air?

Including pathogens such as airborne viruses.

This requires an air filter. Many of us will have seen poorly serviced ones festering away on air conditioning systems. Filers start as ones with big holes only really suitable to keep visible bugs out and then gradually, grade by grade, reach high efficiency particulate air standards (HEPA).

The filter substance, the media, is manufactured in a large sheet. This helps keep costs down and the manufacturer will then test the entire sheet to determine the filter grade. The standard used is EN1822 and after testing the media is graded appropriately. This is good for manufacturing as it means that a sheet produced that fails H14 can be graded appropriately for a lower grade.

Filters produced under this standard are made after the testing. The sheets are then cut and assembled to form the filter but only a batch test is undertaken to check the filters are performing correctly.

It is for this reason that the World Health Organisation (WHO) and Institute of Health Care Engineering and Estate Management (IHEEM) make the following requirement:

“all high efficiency particulate air (HEPA) filters must be individually tested prior to use”.

This is the only way to assure that the filter is actually doing the job it is claimed to undertake.

This is even more important when a complex cartridge filter is made because the filter media is not just clamped into a frame but is also formed and joined into a curve.

Time to answer plainly, do air purifiers work in the real world?

Understand the telltale signals of an inferior air purifier.

It is an established fact that any filter using ULPA media will trap all known pathogens safely within it. Air exiting an ULPA filter is known as Ultra Clean® and is so clean it is near sterile.

The problem arises though that ULPA filters are expensive and also very dense. It takes significant engineering knowledge to produce a system that can pass enough air through an ULPA filter to safely clean the air in a room, especially a hospital ward.

So companies producing air purifiers often reduce the filter efficiency to allow more air through them and thus produce a problem their marketing seeks to turn into a benefit.

If a filter efficiency drops below H14 then it can no longer be assumed to stop all pathogens, especially viruses such as coronavirus (sars-cov-2).

Air purifiers that use ultraviolet light or produce ozone are trying to compensate for an inferior filter.

If we look at ultraviolet light it requires an exposure time. It is incredibly effective with air ducting because the air flows can be uniformly addressed by enclosure and an array that is long enough can be installed to ensure that all the air is irradiated.

However, in air purification systems ultraviolet light is installed to compensate for lower grade filtration to allow higher flows. As the flow increases, unless the ultraviolet array is meters long, the air is moving too quickly to be treated effectively and there can be no assurance that it creates an absolute stop to all pathogens.

The only way to gain an assured stop is to have a filter that is independently verified to at least H14 and designed in a way that things such as ultra violet or ozone are unnecessary. 

We are often asked ‘do air purifiers work?’ The answer is yes, if they are designed and deployed correctly. This is particularly important in health care. By cleaning the air using correctly selected air filters we can improve air quality considerably.

It is possible to maintain Ultra clean air as required without major infrastructure costs or ward closures. In achieving that we hope to help move into a new era. This new era would enjoy the benefits of modern infection control, founded on Germ theory. This would be significantly enhanced by rediscovering aspects of Miasmatic theory and ultra clean hospital air.

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