Back to university: the use of surgical masks at ETH Zurich

Dr Sigel, must I wear a surgical mask when I return to work on campus?
We only recommend wearing a surgical mask if it is impossible to maintain the minimum distance of two metres when working in the laboratory or workshop. 

And what about offices?
The same rule applies, although here the situation is not as critical. Administrative staff will for the most part continue to work remotely from home over the coming period. In addition, there are other potential measures in place for office premises, such as plexiglass screens providing protection between desks.

Why is it advisable not to wear surgical masks as a general rule?
Firstly, because there is a shortage of surgical masks and they are urgently needed in the healthcare service especially. Secondly, because the effectiveness of hygiene masks should not be exaggerated. In particular, they can lull us into a false sense of security and risk neglecting the rules on physical distancing and good hygiene. These rules are essential if we are to overcome the COVID-19 epidemic.

Why is the rule on physical distancing so important?
Here we need to understand how the coronavirus is transmitted: an infectious person can spread the virus through coughing, sneezing or talking into the surrounding atmosphere. The virus is transported in the form of fine droplets or aerosols which can travel up to two metres before sinking quickly to the ground. If these droplets land on us, the virus can enter the body through our mucous membranes.

Can you describe these aerosols?
Aerosols are airborne particles, the smallest of them in the nanometre range – normally invisible to the naked eye, in other words. You may be familiar with aerosols as the puff of breath you can see coming from your mouth on a very cold winter's day. These tiny clouds of aerosols can survive for hours in an interior space, but do not spread for metres.

So surgical masks are not effective?
On the contrary: a surgical mask can reduce the risk of the virus being transmitted directly to others by containing the release of infectious droplets when someone talks. But they are not reliable enough to effectively block all the aerosols. We therefore only recommend using surgical masks in restricted spaces where physical distancing rules cannot be adhered to. Surgical masks are only effective when used correctly, and that is not always straightforward in everyday situations.

What are the main challenges when using surgical masks?
The first problem is putting it on correctly. Here it is important to observe strict hygiene, in other words washing your hands with soap and water beforehand and only touching the masks on the ear straps. But the biggest challenge is to avoid touching the mask while you are wearing it. We all know how often we touch our face, and when your skin starts to itch under the mask … The department of Safety, Security, Health, Environment  (SSHE) has published an information sheet, which includes details on where to obtain the masks and how to use them properly.

Are the masks also intended for private use?
No, surgical masks issued by ETH should only be used at work. Masks for private use can be purchased from pharmacies or wholesalers.

There are now many different types of mask, including those made of fabric, which can be used more than once. Do they offer the same level of protection?
We do not advise the use of masks made of cloth, as they do not offer adequate protection. The Type II surgical masks issued by ETH have a high bacterial filter efficiency and resistance against airborne droplets.

What about respirator masks containing an exhalation valve?
This type of mask is not a suitable means for protecting other people from infection. It actually has the opposite effect: the valve in the mask creates a jet effect that can propel exhaled droplets into the surrounding air.

Some members of the ETH community belong to what is classed as a high-risk group because of pre-existing medical conditions. What advice would you give them?
Vulnerable persons belonging to a risk group should basically continue working from home. If this is not possible – for example because someone manages a critical infrastructure at the university – they must strictly observe physical distancing and good hygiene rules in the workplace. In addition, they must avoid travelling by public transport wherever possible.

But what if the space in the workshop or laboratory is too restricted?
In that case, they should contact us directly [].