Have you ever thought about sanitising your face masks to get a few days more wear? Our new study found out that's not a good idea.

Since the beginning of the COVID-19 pandemic, most of us use two items on a regular basis. The first is hand sanitising products and the second is face masks.

In many cases these two items are our first line of defence against the virus. The only thing standing between us and it. But what if one of these two items had the potential to counteract the other so that it no longer worked?

That’s exactly the situation our researchers investigated in a recent study. Their research looked at the effects of alcohol-based sanitiser vapours on respirator filtration systems, specifically face masks.

Being filtration experts, they understood the technology behind the most commonly used disposable face masks, including the (K)N95 and P2 rated masks, relies on electrostatic charge.

A charge against COVID

Electrostatic charge is the result of friction between two surfaces. It’s what causes the ‘zap’ you sometimes get when touching someone or something. It also features in the famous rub-your-head-with-a-balloon-to-make-your-hair-stand-on-end party trick.

But did you know that this important mechanism is also embedded into your disposable face mask? It works by using an electrostatic field to attract pathogenic particles in the air. Thus, making them hit the surface of the mask’s web of fibres. A trapping mechanism (known as van der Waals forces) then works to capture the particles, trapping them like a sticky spider web.

This mechanism, however, can be weakened by fumes from the alcohols contained in many common sanitising products, like ethanol and isopropanol. Concentrated vapours from these products remove the electrostatic charge.

This kind of event could be disastrous during real-world pandemic mitigation practices. The disruption could possibly allow pathogens like COVID-19 to pass straight through a face mask and reach the wearer.

A lab replication of sanitising hands while wearing a face mask. Someone is rubbing sanitiser on gloved hands below a metal instrument that's holding a face mask.
A common ritual most of us have experienced throughout the pandemic is sanitising our hands while wearing a face mask. This is how we tested this real life scenario in the lab.

Investigating mask care in real-world scenarios

The pandemic has seen an increased use of both face masks and alcohol-based hand sanitising products. There has also been an increase in sanitising of surface areas such as work benches, restaurant tables and hospital surfaces.

Our researchers hypothesised this increased combination of mask and sanitiser might be problematic. But until now, this was only a theory. It hadn’t been scientifically tested.

So, they set out to conduct what we believe to be a world-first study. They looked closely at the real-world impact of vapours from hand sanitisers and alcohol-based cleaning solutions on the performance of single-use face masks.

The same team that established Australia’s first certified testing facility for single-use face masks in response to COVID-19 worked with our Data61 team to analyse their findings. They examined four different strategies that people might use to mitigate exposure to the COVID-19 virus. These included:

  • The use of hand sanitisers while wearing a mask
  • Cleaning of table surfaces while wearing a mask
  • Sanitisation of masks by spraying with alcohol-based solutions
  • Exposing masks to concentrated alcohol-based vapours
A cartoon graphic of four different sanitising and face mask scenarios side by side. The first is a lady sanitising her hands while wearing a mask. The second is a person sanitising a table while wearing a mask. The third is someone spraying sanitiser directly onto the mask. The fourth is a mask soaking in a jar of sanitising liquid. The first two scenarios have green ticks in the top right corner. The third has a yellow exclamation mark. The fourth has a red cross.
The results of our study summarised in a simple graphic.

Should we be worried?

Surprisingly, the findings were not too bad.

The study found disposable respirator masks such as the KN95 and P2 were able to retain their effectiveness after being exposed to a certain degree of alcoholic vapours. After either four hours of continuous exposure to alcoholic sanitiser vapours or one direct spray of sanitiser, the masks still removed 98 per cent of all particles in the breathed in air. Any further exposure had the potential for more serious degradation.

After exposure to a high concentration of alcoholic vapours, this changed. The masks became so compromised they no longer offered protection. This high concentration is quite extreme. A real-life scenario might be sealing your mask in a plastic container with an alcohol-based sanitiser product.

Some people think that exposing their disposable mask to sanitiser overnight will squeeze an extra day of use out it. In fact, it will have the opposite effect by destroying the mask’s charge and hence its functionality. It is always best to use your mask as per the manufacturer’s instructions. And remember that single-use masks are just that.

Breathing easy

Shortages of masks and personal protective equipment have been common throughout the pandemic. If people are going to sanitise and reuse masks in situations like this, we need to understand how the masks will react. Our team suggests that manufacturers should assess the specific effects of different exposures of respirator masks to alcoholic vapours before use.

Literature on this issue painted a somewhat confusing and ambiguous picture about the effect of sanitiser fumes on filtration material. The results of this study will help clarify this and build on existing research. It will also help inform the development of future filtration material around the world.

Most importantly, we now have a better understanding of how best to care for our disposable face masks. Armed with this knowledge, we can ensure our mask’s ‘spiderweb’ remains fully charged and be confident that it’s providing us with optimum protection.


  1. Hi Chris,

    This report suggests in essence to apply learnings from the COVID-19 Pandemic to the upcoming flu season. One has to remember that back in 2020 there was no appreciation of the fact that viruses might be able to spread via airborne aerosols, which only became an issue with the emergence of the highly contagious and deadly “delta” and “omicron” strains of corona virus. It was always known, at least by persons familiar with the subject, that respirators can effectively reduce exposure to aerosolised viral material and possibly reduce the severity of an infection – although that has not been proven either. Referring to “respirators” means face masks with an effective filter medium to capture aerosols and affording a good facial seal, fitted properly. I see many people not doing up the nose clip; this mask will not protect you from aerosols! It is also true that it was nearly impossible to get access to respirator masks in 2020, at the beginning of COVID-19, because there was such a high demand. But these products now become more readily available.

    Thanks Team CSIRO

    Note though that any mask, respirator, surgical or cloth, helps reduce the spread of viral aerosol and hence benefit the population as a whole. That is why this measure was implemented and even enforced during the heights of the pandemic. But protecting you as a wearer directly from aerosols requires a properly fitted respirator mask. I hope this covers the most relevant points.

  2. Hi Wendy,

    To sanitize masks by immersing them in water will heavily affect electrostatic charge of the mask’s filter medium, if the liquid is allowed to penetrate. Most disposable masks will not recover a uniform charge field across the filter medium and hence loose their protection against aerosols. Some less common types can recover a significant amount of charge and provide aerosol protection at a reduced level if appropriate procedures are followed, but no mask will regain anywhere near ‘as new’ performance.

    Team CSIRO

  3. What is the effect of washing the mask by immersing in water, no rubbing , then hanging out in the sun or immersing in a disinfectant solution and hanging out in the sun. I re-use my masks like this. I have never thought of spraying with alcohol .I did a science degree years ago!! I hadn’t realised how masks worked electrostatically.

  4. Would putting the mask in the Microwave for a minute or two sanitize it without destroying its electrostatic properties?

  5. What is your assessment of the recent 2019 WHO report “Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza”? The conclusion from the meta-study is that using face masks provides “a non-significant relative risk reduction” compared to a control group without masks. The WHO report states quite clearly upfront that the single-use surgical/medical mask that so many people are using is “not designed to protect against breathing in small-particle
    aerosols that may contain viruses”. Cloth fask masks are even poorer.

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