Effective Decontamination Methods Critical to Preserving N95 Mask Integrity

Some ways of decontaminating N-95 respirator masks can degrade mask integrity, according to the authors of a recent study.

Findings were published in Infection Control & Hospital Epidemiology.

Due to the global shortage of N-95 respirator face masks, particularly in essential health care settings, clinicians and other medical professionals have had to rely on the reuse of personal protective equipment (PPE).

In the study, some respirator decontamination methods preserved the original filtration capabilities of PPE, while others degraded mask integrity after repeated use. Respirators treated 1-10 times with specific vaporized hydrogen peroxide sterilizers or up to 5 times with decontamination cycles of gas plasma hydrogen peroxide continued to provide protection similar to first-use.

On the other hand, a decontamination process using ultraviolent germicidal irradiance may slowly diminish filtration efficiency. The phenomenon reaches a level "that warrants caution" according to study investigators after 9 treatments.

Additionally, decontamination methods relying on higher concentrations of gas plasma hydrogen peroxide (which is effective in shorter cycles) or longer processing times degraded filtration performance below regulatory standards for N95 masks, which are intended to be able to filter 95% of 300 nanometer particles.

"However, there are still a number of sterilizer systems that are being used on these masks which we don't have information about and therefore can't determine if they keep workers safe," said study lead author Richard Peltier, an associate professor at the Massachusetts Amherst School of Public Health and Health Sciences, in a press release.

According to the press release, Peltier was given funding by the National Science Foundation to study the impact of various sterilization techniques authorized for emergency use in the United States back in May.

"Given the global N95 shortages, clinicians face a choice: wearing a used, and potentially infected respirator, or wearing one that was decontaminated through a process that may affect the integrity of the respirator," Peltier explained.

The tests were conducted using advanced contamination detection instruments and a simple mannequin head in Peltier’s lab to assess if microscopic particles could pass through the masks post-sterilization.

The results suggest that proper mask use in health care settings with prolonged patient contact depends on a nuanced range of factors, some partly outside the control of health care workers.

“Respirators are surprisingly complex matrixes that can be deleteriously impacted by external forces, such as damaging interaction with strongly oxidizing environments. While the intent of decontamination is to furnish a sanitized respirator for clinical reuse, some treatments result in respirators that offer less protection to wearers,” the study team concluded.

Regardless, mask use is still highly recommended for health care settings, outpatient visits, and by members of the broader community who are spending time in close corridors where there are challenges in maintaining physical distance.