Original article (in Slovenian) was published on 25/9/2025; Author: Eva Gračanin
Polona Kogovšek from the National Institute of Biology explains that exhaled viruses are not present in the air as individual particles but are surrounded by a watery envelope within droplets. These droplets, released when breathing or speaking, are much larger than the virus itself, so the mask captures them and prevents the virus from spreading.
The Planet Lepote website ran an article on 9 September claiming that “the SARS-CoV-2 virus measures about 0.1 micrometres, while the pores in most masks are 80 to 500 times larger,” and therefore viruses “pass through them easily – similar to sand falling through a fishing net.”
The article cited some findings of a study summarized the previous day by the British daily The Guardian. This study, published on May 1 last year in the peer-reviewed scientific journal Environmental Pollution, examined the release of microplastics and chemical additives into water from various types of disposable surgical masks and filtering face pieces.
The study’s authors explained at the outset that masks help limit the spread of bacteria and viruses and reduce the risk of their transmission, because they provide very effective filtration of particles and droplets produced when coughing, sneezing, or speaking. They found that all protective masks they tested released microplastics, with FFP masks releasing three to four times more particles than surgical masks.
According to a paper published in 2021 in the peer-reviewed journal Scientific Reports, the SARS-CoV-2 virus has an average diameter of about 0.097 micrometres without the spike proteins on its surface that enable it to bind to human cells. Including the length of the spike proteins, the virus reaches a diameter of 0.143 micrometres.
Polona Kogovšek, a senior research fellow at the National Institute of Biology, told Razkrinkavanje.si that the pores in most protective masks are larger than the virus but not larger than the droplet containing the virus.
She explained that exhaled airborne viruses are not present as individual particles but are surrounded by a watery envelope – droplets. These droplets are much larger than the virus, so , when a mask wearer exhales or speaks, the mask captures them and prevents the virus from spreading. The pore size of masks is not the decisive factor in determining the level of protection against viruses; more important is the charge of the fibres from which the mask is made, she said.
Based on comparative studies, experts have found that wearing masks effectively prevents the spread of viruses. The degree of protection provided by masks varies across studies: “The most effective are FFP2 masks or respirators, because the material from which they are made is more densely woven.”
She further explained that N95 masks, which are also respirators, consist of several layers of densely woven nanofibers that create a large surface area and attract small droplets. The pores in the material range from 10 to 65 micrometres, allowing for effective filtration of viral particles.
Kogovšek shared with Razkrinkavanje.si with two studies on the effectiveness of masks in preventing the spread of infections. One study, published last year in the peer-reviewed journal eBioMedicine, compared the effectiveness of respirators, surgical masks, and cloth masks in COVID-19 patients. It found that respirators reduced the risk of transmission by a factor of twenty, while surgical and other masks also reduced the risk as well, though less effectively.
Similar findings came from a study published last year in the scientific journal Nature. The authors explained that FFP2/N95 respirator masks, when properly fitted and worn by both infected and healthy individuals, achieve about 96 percent filtration efficiency. Surgical masks are less reliable, allowing on average about one-third of aerosol particles – airborne particles of matter – to pass through.
The authors of a paper published in August 2021 in the NIB’s professional bulletin also found that hygienic masks made of different fabrics (cotton, silk, synthetics), with larger fibres and no electrostatic charge, are less effective at filtering particles than medical masks and respirators. Nevertheless, they still reduce the spread of infections. According to this article, respirator masks of the types FFP1, FFP2, FFP3, and KN95 also hold back fine aerosols, while surgical masks primarily protect against droplet transmission of pathogens.
We have informed Planet Lepote of our findings and will publish their response once we have received it.
The claim that “the SARS-CoV-2 virus measures about 0.1 micrometres, while the pores in most masks are 80 to 500 times larger,” which supposedly means that “viruses pass through the material easily,” is false.
