Today, almost all citizens must wear masks, and questions about how long these protective elements are worn and how to use them safely are more intense.

The COVID-19 pandemic forced Western society to accept the widespread use of masks among the population. As we learn more about the coronavirus (especially the transmission of asymptomatic stages), and the lack of these protective elements is easing, health authorities and governments in many countries have moved from discouraging them to recommending or even forcing their citizens to use them.

This change in people’s perception of not being used to wearing masks has generated doubts about their correct use and the reasons for choosing certain types of masks among citizens. The authorities lacked a large-scale educational campaign to use them correctly, and did not eliminate this chaotic atmosphere at all.

The unresolved problems that have become more important from now on include problems related to the reuse and disinfection of masks. These two aspects not only caused great suspicion among citizens, but also among health professionals. Due to the lack of inventory, health professionals were forced to reuse the masks, despite violating the manufacturer’s recommendations.

Not ideal

Ideally, the mask should be reused and discarded after each use, but we live in a pandemic situation, which is far from ideal. Today, there are not enough masks on the market for every citizen to wear new masks every time they leave home. Therefore, although the use of facemasks is not recommended as a one-time measure, the reuse of masks is the norm in everyday life.

Unfortunately, there is no clear answer to the questions asked by citizens and health professionals about the repeated use and disinfection of masks. The reason is simple: there is little scientific research that can evaluate how the mask degrades within the recommended time of use, or how the different disinfection methods for coronavirus affect these elements.

Before the pandemic, almost all health care professionals wore masks and it took several hours before they were discarded. However, the situation is quite different now, and many people want to know what the recommended maximum time for mask use is, or what disinfection measures are recommended for mask reuse.

There are many types of existing masks, which cannot provide universal and effective suggestions for all masks. Not only because there are different types (hygiene, home, surgical, FFP, N95, etc.), but even within each type, there are different models with specific materials and characteristics. To promote understanding of the general guidelines, we will break down the most important data according to type.


Reusable hygienic home fabric

These masks can be reused indefinitely, as they can be sterilized after each use by a cleaning cycle with common detergent at a temperature of 60ºC or more. In any case, it should be verified that the cleaning process does not change the characteristics of the mask. For example, cotton can shrink and make the mask made of this material smaller, and it cannot completely cover the face.

Another option is to dilute the mask with hot water in bleach 1:50 for 30 minutes. Then wash with soap and water, rinse well to remove residual bleach, and dry. The disadvantage of these cloth masks is that they are often less effective at blocking airway drops than surgical masks.

Surgical and hygienic disposable cellulose

The recommended wearing time for these cellulose or polypropylene masks is very short: approximately four hours. As a result of breathing or sweating, they become damp, which changes the materials and filters that are no longer used. Therefore, it should be discarded after such a period of use or when it becomes noticeably wet or deteriorated. They also cannot be cleaned because they can be damaged when they are cleaned.

What happens if we wear one of these masks for less than four hours without getting wet or damaged and we want to use it again another time? To answer this question, it is recommended that you pay attention to the survival time of the viruses in these masks. A scientific study published in the journal The Lancet Microorganisms found that the SARS-CoV-2 virus can survive for a long time outside of surgical masks.

Specifically, they observed that after 7 days from the start of the experiment, they detected 0.1% of the amount of virus initially detected. Surprisingly, due to the presence of materials with different characteristics, the virus survives only a few hours inside the mask, so it is not suitable for the survival of the coronavirus.

One option to eliminate the possible presence of virus and residual moisture in the mask only after a period of use is to place the mask in a secluded location, which can be placed in the sun for 7 days until the next use. Why? Because in the sun, the survival time of the virus is considerably shortened. After this period of time, under these conditions, it is very unlikely that a certain amount of virus can be infected.

If we do not want to wait a week, we can sterilize these masks quickly and safely by placing them in special bags with oven-sealed lids (to avoid contamination of other materials by viruses) and heating them to 70ºC. Bake in the oven for 30 minutes. Studies of other viruses and SARS-CoV-2 have found that, in these masks, temperatures equal to or higher than 70ºC completely destroy these viruses in 30 minutes. In addition, it has been observed that even after multiple cycles of sterilization through this method, the surgical mask continues to maintain its function. In any case, it should be emphasized that discarding the mask after use is the best and safest thing to do.

FFP and N95

These used in the medical field are not suitable for repeated use. Although the recommended usage time depends on the model, manufacturers usually recommend eight hours of continuous use. Moisture released by breathing or sweating gradually interferes with the mask filter, which can make breathing difficult and affect its effectiveness after a period of use.

In addition, long-term use will also affect the fit of the mask and the gradually lengthening strap. Although several health agencies do not recommend disinfection and reuse, agencies such as the Centers for Disease Control and Prevention (CDC), or several scientists are aware that it is better than health professionals in the event of a shortage. Reuse and disinfect these masks (in the workplace rather than at home) so that they are no longer used.

The Federation of Scientists has compiled the latest scientific information on disinfecting these masks, but due to the lack of scientific knowledge on this issue, no specific method has been approved. In general terms, the best disinfection procedure is to sterilise them in ultraviolet rays, due to the heating of the hydrogen peroxide or heat of 70ºC, because these methods have a significant antibacterial effect and basically do not change the fit of the mask after several cycles. On the other hand, they will avoid certain decontamination methods, such as dry heat at 160ºC, alcohol, lye immersion, microwave radiation and water and soap, as they can cause significant degradation of the filter and/or change the filtration method.

Most of these methods cannot be used at home, but one draws attention to their simplicity and effectiveness: heating the mask in the oven at 70ºC for 60 minutes. Afterwards, 70% alcohol should be applied only to the metal part of the mask to adjust the nose, because the virus is there to resist the heat for longer. This process can guarantee the destruction of the virus, and in the evaluated model, the fit and filter of the mask cannot be changed in 1-2 cycles, although it can have different effects than in other models.

To avoid contamination with other household items, it is recommended that you use a sealed oven bag and insert the mask immediately after returning from your home. Again, it is important to emphasize that it is best to discard it after use to avoid any risk of contamination by viruses.