Protective masks could be effectively disinfected in the home, study finds

Researchers conclude that homemade masks plus some medical masks can withstand simple disinfection without substantially reducing their effectiveness.

A fresh study has found that disinfecting homemade masks by heating them might not exactly significantly reduce their effectiveness - and that some medical masks can undergo this technique and still be effective.

The research, published in the Journal of the International Society for Respiratory Protection, may be valuable for reducing the pressure on stocks of medical masks through the coronavirus disease 19 (COVID-19) pandemic.

In line with the World Health Organization (WHO), the virus that causes COVID-19, extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is mostly transmitted by coughing and sneezing.

Droplets of saliva and discharge from the nose can carry the virus. It can be directly passed on if, for example, someone with the infection coughs or sneezes, and someone else in close proximity breathes in the resulting droplets.

The virus may also survive on surfaces that the droplets land on. Transmission may appear if a person makes contact with the droplets on a surface and the virus gains usage of the person’s body - if, for example, the individual touches their face.

Addititionally there is evidence that some persons with the infection experience few, if any, symptoms and may still be in a position to spread the virus.

As a consequence, the Centers for Disease Control and Prevention (CDC) have recommended wearing cloth face coverings in conditions when it is difficult or impossible to maintain a distance of 6 feet between people.

They urge people to create their own face masks and reserve surgical masks and N-95 respirators for healthcare workers. The CDC have produced helpful information on how to generate a face mask in the home.

In light of the advice, the researchers behind the present study set out to investigate means of disinfecting masks safely - killing any SARS-CoV-2 without reducing the potency of the masks as time passes.

They studied means of disinfecting homemade masks and those for healthcare workers, as reusing masks may help ease pressure on dwindling stocks.

The analysis authors cite previous research demonstrating that heating masks to 70oC (158oF) works well at killing the SARS-CoV-2 virus.

While other disinfection techniques have also proven effective, heating can be achieved by anyone with usage of a stove.

To test how effective masks are after disinfection by heat exposure, the authors applied different masks to the heads of mannequins made to simulate the drawing of breath.

Because it had already been established that heating to 158oF could kill SARS-CoV-2, the researchers didn't need to use the virus. Instead, they used soot from a kerosene lamp, the particles of which are roughly the same size as SARS-CoV-2 particles.

The authors then tested two disposable N-95 respirator masks, one disposable surgical mask, and three homemade masks, from a cotton dress, a cotton sweater, and polyester cloth.

They measured the levels of soot outside the mannequin and in the air that had passed through the masks.

They repeated the tests, changing the tightness of the masks and using mannequins of different materials, plastic or silicone, to simulate the softness of the human face.

The researchers figured - if fitted tightly on a plastic mannequin - one N-95 respirator and the surgical mask could be disinfected by heat exposure ten times without losing their effectiveness.

The N-95 mask achieved a filtration efficiency of 95%, as the surgical mask achieved 70%.

The other N-95 respirator failed after being repeatedly applied to the mannequin.

However, when the authors used the masks on the softer, silicone, mannequin with a fit that a person would normally use, they discovered that filtration levels were significantly lower - at around 40% for both surgical mask and the N-95 respirator.

When the team used homemade, cotton masks on the softer mannequin, they learned that the filtration efficiency was 55% - better than either the surgical mask or the N-95 respirator when used with a regular fit.

Heating the homemade masks also had no influence on their filtration capacity.

Finally, the authors explored the potency of homemade nose clips applied to the mask. They found that, when applied to disposable masks with a regular fit, the nose clips substantially increased filtration efficiency: to 98% for the N-95 mask or more to 88% for the surgical masks.

The researchers acknowledge that their study was relatively small and didn't account for the ways that a person’s breathing and movement change the fit of a mask.

Nonetheless, the authors - who hail from Columbia University’s Lamont-Doherty Earth Observatory, in Palisades, NY - note, “Everything we realize so far suggests that wearing almost almost any mask in public is better than nothing, that a tight fit is most beneficial, and that, with certain limits, many types of masks could be reused beyond medical settings.”