Do Surgical Masks Work? The Effectiveness of Wearing Face Masks Against Infection Transmission
Adjusting to the wearing of facemasks has been difficult for some. Long periods of wear and difficulty reading others’ facial expressions has led people to wonder ‘do surgical masks work?’, wanting to know that they are wearing face masks for good reason.
There is strong evidence for surgical masks being effective against transmission of infections like Covid-19, which travels in droplets from one person’s mouth or nose to another’s. Here, we’ll look at the effectiveness of respirators and surgical masks—do they work? How effective are they?
How is Covid-19 transmitted?
Covid-19 is one of many viruses in a group called coronaviruses that attack the respiratory tract in humans and animals. Coronaviruses can range from mild, like the common cold, to more lethal, like SARS. Covid-19, like the common cold, is transmissible in two ways:
- Through droplets or aerosols that come out of an infected person’s nose and mouth when they breathe, speak, cough, or sneeze.
- Through fomites (inanimate objects that bear infectious particles) that carry Covid-19 particles, usually from someone coughing onto them or transmitting droplets from their hands to surfaces.
A 2020 study found that droplets from coughs and sneezes are the main cause of transmission of Covid-19 between people. It goes on to recommend that caregivers and those attending to patients with Covid-19 should be fitted with an N95 respirator or one of higher level protection like a KN95 respirator or FFP3 respirator.
Coughing isn’t a surefire sign of the presence of Covid-19, though. The UK government estimates that one in three people with the virus doesn’t show any symptoms at all. Additionally, people who have been vaccinated against Covid-19 can still become infected. This is why the government recommendation is that everyone should use face masks when indoors and when they can’t practice social distancing.
How do face masks help?
Face masks work by presenting a barrier between a person’s nose and mouth and the external environment. This means that surgical masks like Type I, II, and IIR face masks catch airborne droplets that come out of the nose and mouth as a person exhales. Respirators like FFP3 masks and KN95 masks create a seal around a person’s nose and mouth so that when they breathe in air is filtered through but particles of a certain size are blocked by the layers of the mask.
The Effectiveness of Different Types of Masks
The type of mask you choose and how you wear it is very important. Incorrect mask-wearing can lead to leakage and render it ineffective. In a 2020 study, researchers were able to visualise leakage from different mask types using smoke pumped through the face of a mannequin to mimic droplet dispersion.
The study found that using no mask allowed the smoke jet to reach 8ft from the mouth of the mannequin. Bandanas allowed the smoke jet to reach 3ft 7”, and folded handkerchief masks resulted in dispersion as far as 1ft 3”. A commercially available cone-type mask resulted in a smoke jet reaching 8”.
| Mask Type | Average Jet Distance |
|---|---|
| Uncovered | 8ft |
| Bandana | 3ft 7in |
| Folded handkerchief | 1ft 3in |
| Commercial mask | 8" |
So wearing a mask significantly reduces the distance to which particles can travel when you exhale. Not only that but the quality and fit of the mask makes a big difference too.
Disposable masks are designed to pass stringent testing to be approved for sale to consumers, unlike fabric masks which do not always abide by the same standards. Because of this, it’s best to always wear a disposable face mask when you can rather than a fabric mask.
Check that the face masks you buy are manufactured by a genuine company that meets British Standards. Look for the EN number on the product or packaging, or ask the retailer to supply you with it.
- Type I, II, and IIR face masks should bear a British Standard EN 14683:2019+AC:2019 certification.
- FFP respirators must bear a British Standard EN 149:2001+A1:2009 certification.
Different types of face masks are used for different reasons. Surgical masks like Type IIR face masks are used by people to protect others from inhaling their exhalations. Respirators like FFP3 masks and KN95 masks are used to protect the wearer from inhaling airborne droplets. In fact, a study in Addenbrooke’s Hospital in Cambridge found that when nurses were required to switch from Type IIR face masks to FFP3 respirators, cases of hospital-acquired SARS-CoV-2 infections dropped by 100%.
Other Evidence for Face Mask Efficacy Against Covid-19
A 2021 review of the effectiveness of mask-wearing highlights the wealth of epidemiological studies that have taken place across the world in light of the Covid-19 pandemic showing the effectiveness of mask-wearing in communities. Some of the many examples in this review include:
- During a breakout of Covid-19 at an army base housing 382 US soldiers stationed in Guam, mask-wearing reduced the risk of infection by 70%.
- Among 389 close contacts of some 211 people with Covid-19 in Bangkok, mask-wearing reduced infection risk by 77%.
- Out of 139 customers to a hair salon where two stylists with symptomatic Covid-19 were working, zero infections were recorded in the 67 people contacted for follow up, all of whom wore masks to the salon.
- Due to mandatory mask-wearing indoors, cases in the country of Canada declined weekly by an estimated 25%-40%.
Researchers conducted an experiment on the effectiveness of face masks in preventing airborne transmission of Covid-19, published in 2020, using different types of masks. Two mannequin heads were placed facing each other in a control chamber with one attached to a compressed nebuliser that would emit (‘breathe out’) an infectious cloud. The other head was connected to a ventilator designed to collect virus particles.
It should be noted that both mannequins were closer to each other than social distancing would allow and that they were contained within a small, unventilated space.
The study found that when the mannequin was equipped with different types of masks, the volume of viral droplets and aerosols ‘inhaled’ reduced.
The N95 mask (the most protective mask used in the study) was found to filter out the most viral particulate, by 80%-90%, whereas the cotton mask reduced the number by only 20%-40%. When the surgical mask was used on the exhaling mannequin, the volume of viral particulate inhaled by the receiving mannequin was reduced by 50%.
It’s clear that masks offer significant protection against transmitting Covid-19, and the WHO recommends using them as part of a strategy to slow the spread of Coronavirus and save lives. But it also says they shouldn’t be relied on alone.
The best way to protect against transmitting Covid-19 is to practice social distancing where possible, wash hands more regularly for 20 seconds at a time, use hand sanitiser when you can’t wash your hands, and keep surfaces and touchpoints clean with a disinfectant spray.
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