Can air purifiers reduce infection risk?

The short answer is yes, air purifiers can – and have been proven to – reduce airborne infection risk.  But, you need to understand a lot more about the different types of infection before making your own assessment.

Firstly, we need to understand how infection spreads.

Lets begin by talking very simple language which will help to make this article understandable to all.

There are 5 main categories of infectious agents which consist of viruses, bacteria, fungi, protozoa and helminths. Basically, the key common ones of concern are viruses, bacteria & fungi. All these infectious agents are types of microbes. Now – microbes can be found all over our body surfaces, including skin, gut and mucous membranes. From the minute we are born, microbes begin to colonize our bodies which are unique and play a key role in digestion and prevention from disease. Most microbes are perfectly fine and have the purpose to help growth and survival, but in some instances harmful microbes will enter our bodies, begin to multiply and will make us sick.

In response to an infection, your immune system springs into action. White blood cells, antibodies and other mechanisms will fight to get rid of the foreign invader. Many of the symptoms that make a person suffer during an infection – fever, headache, rash – result from the activities of the immune systems trying to eliminate the infection from the body.

Viruses make us sick by killing cells or disrupting cell function. Bodies respond with fever (heat inactivates many viruses), the secretion of a chemical called interferon (which blocks viruses from reproducing), or by getting the immune system’s antibodies and other cells to target the invader.

Disease, which typically happens in a small proportion of infected people, occurs when the cells in your body are damaged as a result of infection, and signs and symptoms of an illness appear. For example, a cold, headache, flu or similar. 

These are some of the different microbes which cause infections.

As mentioned earlier, there are five major categories of infectious agents: Viruses, bacteria, fungi, protozoa, and helminths.

Viruses – Viruses are tiny and range in size from 20 to 400 nanometres in diameter. They are packets of nucleic acid, either DNA or RNA. These are smaller than bacteria and cause a multitude of diseases ranging from the common cold, measles, chicken pox, herpes, influenza, through to SARS and AIDS.

Bacteria – These microbes are 10 to 100 times larger than viruses and are self-sufficient. One-cell organisms are responsible for illness such as strep throat, tract infections and tuberculosis.

Fungi – many skin diseases such as ringworm and athlete’s foot are caused by fungi.

How are these agents spread?

Microbes which cause illness will normally enter into our bodies through the eyes, mouth, nose or other openings and can be spread through varying means, such as airborne transmission, physical contact, food, water or even animals & fleas.  


When residue from evaporated droplets or dust particles containing microorganisms are suspended in air for long periods of time, infection can spread by airborne transmission. Droplets will faithfully follow air flow, or may just hang around suspended, and will easily enter through or nose or mouth and into our lungs & bloodstream, often leading to illness.

Contact – Direct/Indirect

Direct contact includes person to person through touches, coughs, sneezes, body fluids and then even animal to person or mother to unborn child. Diseases transmitted this way include cold sores, herpes etc. Pathogens can also be spread by indirect contact when an infected person touches a surface and leaves behind microbes which are then transferred to another person who touches that surface.

Insect bites

Mosquitoes, fleas, lice or ticks carry germs from host to host. The most common for human infection is the mosquito, which transmits malaria and other harmful diseases.  .

Food or Water contamination

Food, water, blood or other such vehicles may also spread harmful pathogens. E Coli or Salmonella for example will easily enter the digestive system and cause nasty sickness symptoms.

What proportion of infections are attributed to airborne transmission?

This is a complex question to accurately answer, and you need to look at this in connection with the actual infections which tend to be transmitted through the air, such as:

  • The common cold, Strep, MRSA, chickenpox, mumps, measles, whooping cough, tuberculosis (TB), anthrax, meningitis, influenza, SARS (Covid), & other respiratory related infections. (Quite a lot).

In this light, a very high % of harmful illnesses and infections are in fact transmitted through the air. This study is an interesting read.

  • “ Virtually all outbreaks of nosocomial aspergillosis are attributed to airborne sources” (R-P. Vonberg and Gastmeier, 2006)
  • “More than 1/3 of all nosocomial infections possibly involve airborne transmission at some point” (Kowalski, 2007)
  • “Airborne transmission accounts for 20-24% of post-operative wound infections” (Kundsin, 1980)

Where do air purifiers come into play and help reduce infections?

In layman’s terms, airborne infections can be attached to aerosol droplets which will be a specific size. A virus may range from 20 > 400 nanometres in size, whilst a bacteria particle will be 10x larger (plus).

If an air purifier includes HEPA 13 or HEPA 14 grade filtration technology, then 99.99% of particulate matter as small as 0.1 > 0.3 microns will be captured in a single pass. Practically, this means that any bacteria droplets are likely to be trapped by the filter and more than 99% of virus particles will be de-activated and prevented from further transmission.

So, if your air purifier is using a high grade of HEPA filtration and is suitable for the room size to achieve 4 plus air filtrations per hour, you will massively reduce the risk of infection and spread of harmful aerosols.

Is there any proof?

There is a lot of proof, especially from our many clients who have implemented. For instance, one client operates a large hospice group for end of life care. They were struggling with high infection rates from Covid and Flu so they decided to implement Zonitise air purifiers throughout the entire building which featured H14 filters and purified the air a minimum of 5x per hour. They stopped wearing masks after they implemented the air purifiers, and have since recorded zero cases of Covid in the hospice.

You can see some further white paper examples here:

Interested in finding out more?  Why not reach out to one of our advisors for a chat.

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