In a study published by the JAMA Network Open, researchers at the Center for Health Sciences of the University of Oklahoma reported about how efficient they were two techniques of disinfection of masks.
According to the publication, the findings suggest that, to sterilize the mask, the mask type and the method of sterilization influence the efficiency of filtration later, the researchers said, while noting that the greatest reduction in filtration efficiency after sterilization occurred with surgical masks.
In the study, the researchers sterilized with plasma vapor hydrogen peroxide (H2O2) and measured the filtration efficiency of N95 masks and KN95, which remained at over 95%, but this percent was reduced to use the same method with surgical masks.
When you use a method of sterilization alternate, this time with chlorine dioxide (ClO2), the filtration efficiency remained above 95% for the N95 masks, but for the surgical masks and KN95, the filtration efficiency was reduced to less than 80%.
“The treatment with H2O2 showed a small effect on the efficiency of filtration-general of the masks tested, but the treatment with ClO2 showed a marked reduction in the efficiency of filtration-general of the masks KN95 and surgical masks. All the changes of pressure drop were within the acceptable range” describe the researchers. In principle, the mask KN95 are similar to the N95, but manufactured under the standards of the regulations in china are not considered as reliable on this side of the world.
To carry out the comparison, neutered, five masks of each type with H2O2 or CIO2. Was then placed in a test chamber and nebulizaron with a salt spray to evaluate both the filtration from the outside to the inside and vice versa, as well as the decrease of pressure. The researchers used a meter of particles of mobility to measure the concentration of the number of particles of 16.8 nm to 514 nm. A pressure drop acceptable was defined as a fall of less than 1.38 inches of water (35 mm) by inhalation.
While the changes in the pressure drop were within the acceptable range for the three types of masks are sterilized by any of the methods, the sterilization with H2O2 produced the smallest reduction in the filtration efficiency in all cases. After sterilization with H2O2, the filtration efficiencies were 96.6%, 97.1% and 91.6% for surgical masks N95, the KN95 and surgical, respectively. In comparison, the filtration efficiencies after sterilization with ClO2 were 95.1%, 76.2% and 77.9%, respectively.
The study did not evaluated the effect that they might have sterilizations repeated in the facial masks, so that will be needed further studies on this topic.