Masks are helpful to protect oneself and even more to protect others. Importantly, masks can offer some protection to healthy wearers; they can protect healthy people from sick wearers who seem to look healthy.
People believe that they are contagious only if you have symptoms, but not so. When infected with SARS-CoV-2 the novel coronavirus that causes COVID-19, most people don’t show any symptoms for several days or even well beyond a week. Some people never show any symptoms at all.
Wearing a mask can protect one from other people, and other people from one. If all wear a mask, all protect each other. But this protection varies from one type of mask to another.
Where COVID-19 is concerned, masks can reduce pathogen circulation from/to the mouth and nose. They can also serve to remind one not to touch the face, thus preventing transmission of pathogens from the hands to the mouth, nose, or eyes.
Different Kinds Of Masks
There are three major kinds of masks: non-medical, medical/surgical, and N95. But research comparing them is imperfect (difficult to conduct a perfect randomised trial of masks during a pandemic). Much of the evidence is from hospitals, where the risk of patient/worker transmission is much higher, and so this evidence doesn’t always apply to non-hospital settings including the general public places.
- Non-Medical Masks
These include a variety of masks: those made at home (typically cloth masks) and others. Their potential benefit varies widely depending on the number of layers, the fit, and the manner in which they’re cleaned. Level of virus protection is typically-low to moderate. They are easy to breathe through and can be purchased or made but their efficacy depends on the material used and way of crafting.
- Medical Masks Or Surgical Masks
Surgical masks vary widely in efficacy, being able to filter between <10 per cent and 90 per cent of droplets. But they fit loosely than the N95 respirators and side leakage is a major risk. They appear to offer only minimal to moderate protection for the wearer but good protection for others if the wearer is sick. Level of virus protection is moderate to high. These masks are not tested for protection against small particles, however, but the public generally think they have been tested, and that is a danger.
- N95 respirators
N95 masks (called ‘respirators’) are the most common variety of respirators.
N95 respirators are tested and standardised. They provide a one-two punch of filtering out small particles and sealing the face with a tight fit. The level of virus protection is high to highest. They are tested to make sure they block at least 95 per cent of particles as small as 0.3 microns. Other varieties of respirators include N99 respirators, which block at least 99 per cent of particles as small as 0.3 microns. But SARS-CoV-2 particle size ranges from 0.07 to 0.09 microns so that even N95 and N99 respirators cannot give full protection. Those respirators still have a significant efficacy against particles as small as 0.01 microns, compared to surgical masks that have poor efficacy against particles between 0.04 and 0.2 microns.
In times of shortages, available N95 respirators should go to healthcare workers.
The masks, however, can be worn only after learning how to wear them correctly. They fit tightly and are uncomfortable to wear, causing headaches and skin reactions. N95 respirators are notoriously difficult to fit correctly — to the point that, in medical settings, the fit is tested with instruments to ensure they are fully effective.
Protection from Masks Compared
Though there is some evidence that both N95 respirators and surgical masks help protect the wearer from others with COVID-19, the extent of the protection is not correctly known and there is no evidence for non-medical masks. There isn’t a lot of peer-reviewed data available yet, but preliminary studies suggest that both N95 respirators and surgical masks help protect wearers. This evidence was gathered in healthcare settings, though, and applicability to other settings is uncertain.
Homemade masks have stronger evidence for protecting others from you than for protecting you from others. Studies have shown that although surgical masks are around three times better at blocking microorganisms than homemade masks, the latter does have some efficacy. But this efficacy varies based on what the homemade mask is made of and how it’s worn.
When worn by the infected, surgical masks help prevent the spread of a variety of infectious droplets, including droplets carrying influenza viruses and previously known coronaviruses.
N95 respirators are the best at reducing the risk of transmission of respiratory viruses, unsurprisingly. An observational study of COVID-19 in China found that 10 out of 213 medical staff without masks were infected, versus 0 out of 278 medical staff with N95 respirators.
A meta-analysis of four randomised trials found low-certainty evidence that, in the context of non-aerosol-generating care (not exposed to aerosol from COVID-19 patients), N95 respirators and surgical masks both protect healthcare workers similarly against viral respiratory infections (including by coronaviruses). Consequently, N95 respirators, when in short supply, are given to high-risk, aerosol-generating procedures. But then again, in a particular case, when researchers looked at 41 healthcare workers exposed to aerosol from patients with COVID-19, they found that all 41 tested negative, even though only 15 per cent of them wore N95 respirators (85 per cent wore surgical masks). So the evidence is not clear cut and certain, and this may also be due to the varying settings and specific factors in them.
Reusing masks
- Extended use is better than reuse because reuse involves touching the mask and potentially the face. A person can wash and reuse cloth masks. One shouldn’t reuse disposable masks, but if one must, one should at least store them in an area exposed to airflow for three days between uses.
- Because N95 respirators are made for one-time use, reusing them after decontaminating them is not to be done. The fit could worsen, and many methods of disinfection may result, which means that after the first use what one may be wearing could be an infected mask. If healthcare workers, lacking supplies, need to reuse N95 respirators, then those should be stored in an area with sufficient airflow for 72 hours between uses, in order to exceed the expected survival time of the novel coronavirus.
For any mask, the longer it is used and the more often one reuses it, the less effective it becomes.
Storing and Washing Masks
- Used disposable masks should be stored (for at least three days between uses) where they can breathe.
- One can wash cloth masks (but not surgical masks or N95 respirators) with soap and water and dry them on high.
- Heat at 56°C (133°F) kills the SARS coronavirus, closely related to the novel coronavirus, at around 10,000 units per 15 minutes
A study found that the efficacy of cloth masks dropped after several washing and drying cycles — by 20 per cent after the fourth washing and drying cycle, for instance. The pores within the cloth can change in size and shape, and ear loops can get stretched out, worsening the fit.
Disinfecting the Masks
- with alcohol or bleach
Masks are not be disinfected with bleaches and brand-name products such as Clorox, Lysol, or Purell. These often include a type of chloride compound that kills viruses by disrupting intermolecular interactions within the virus. But chlorine-based solutions and 75 per cent alcohol solutions interrupt the static charge that supports filtering. Moreover, the gases used in bleaching remained even after multiple strategies were tried to remove them, making skin and respiratory irritation likely.
- with sunlight/UV
There isn’t much of research to show the effect of sunlight as a disinfectant, but medical UV sterilisers can be effective. UVC machines may be effective as well but are more dangerous.
Studies show that UVC can inactivate a variety of viruses, including the SARS coronavirus (a close cousin of the novel coronavirus). Unfortunately, UVC devices are much more dangerous than other UV sterilisers (especially for non-professionals). They can cause severe sunburn and retinal damage.
Sunlight is not equivalent to high-powered UV sterilising cabinets or towers. The sunlight that comes to the earth is devoid of UV rays because of the ozone layer that is present in the atmosphere. Sunlight is not an effective solution as (1) it has insufficiently strong UV rays and these won’t penetrate deeply enough to disinfect the entire mask; (2) sunlight exposure often means outdoor exposure, in which case the mask may accumulate moisture or even get infected; and (3) sunlight has not been studied for this purpose as UV machines have been.
Studies have shown that high levels of ultraviolet germicidal irradiation (UVGI) can inactivate influenza viruses and single-stranded RNA viruses (like the novel coronavirus). According to Nebraska Medicine, which is a partner of the University of Nebraska Medical Center, it has developed a method of using UVGI to decontaminate N95 respirators. But the UVGI exposure increases particle penetration by 1.25 per cent; even though this doesn’t make the N95 respirators ineffective, it weakens the layers of material and increases the chances of the straps breaking over time.
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- Steam can be used to decontaminate masks but at the cost of reducing their filtering efficiency.
- Studies have used hot air to disinfect N95 respirators, but easy mistakes can result in imperfect decontamination, a reduction of the mask’s filtration efficacy, or accidents (fire).
- Disinfecting the mask in a microwave is not to be done if it’s an N95 respirator, a surgical mask, or a mask with any metal or plastic in it. Though this kills viruses like the avian pneumovirus and even reduces the presence of HIV and the hepatitis C virus in fluids after two minutes of heating at 800 watts, there are risks: melting, fire, and inadequate decontamination.
- Disinfecting the mask in a freezer may not be useful as previous coronavirus strains appear to be stable at low and freezing temperatures for an indefinite period. Direct evidence on the novel coronavirus is lacking.
Can masks cause breathing issues?
N95 respirators and multi-layered cloth masks are more likely to contribute to breathing issues than are surgical masks and loose-fitting single-layer cloth masks. Major breathing difficulties have been associated with N95 respirators.[
Masks have to balance protection with breathability, to avoid causing more harm than good: the harder one breathes, the greater the risk of side leakage. If a person has pre-existing breathing difficulties, then he may be unable to wear certain masks for more than a very short period.