Ultraviolet C light ideal for optimal decontamination of individual N95 respirators

Zi YangJiang and associates from the Department of Otorhinolaryngology–Head and Neck Surgery, McGovern Medical School, Houston, Texas, USA carried out the present study with the sole purpose to evaluate the effectiveness and ease of N95 respirator decontamination methods in a clinic setting and to identify the extent of microbial colonization on respirators associated with reuse.

The authors conducted a prospective study in which a total of 15 N95 respirators were randomized to a decontamination process (time, dry heat, or ultraviolet C light [UVC]) in outpatient clinics. Each respirator was re-used up to 5 separate clinic sessions.

Swabs on each respirator for SARS-CoV-2, bacteria, and fungi were obtained before clinic, after clinic and post-treatment. Mask integrity was checked after each treatment (n = 68). Statistical analyses were performed to determine factors for positive samples.

The results showed that -

a. All three decontamination processes reduced bacteria counts similarly.

b. On multivariate mixed model analysis, there were an additional 8.1 colonies of bacteria (95% CI 5.7 to 10.5; p < 0.01) on the inside compared to the outside surface of the respirators.

c. Treatment resulted in a decrease of bacterial load by 8.6 colonies (95% CI -11.6 to −5.5; p < 0.01).

d. Although no decontamination treatment affected the respirator filtration efficiency, heat treatments were associated with the breakdown of thermoplastic elastomer straps.

e. Contamination with fungal and SARS-CoV-2 viral particles were minimal to non-existent.

Therefore, it was concluded that "Time, heat and UVC all reduced bacterial load on reused N95 respirators. Fungal contamination was minimal. Heat could permanently damage some elastic straps making the respirators nonfunctional. Given its effectiveness against microbes, lack of damage to re-treated respirators and logistical ease, UVC represents an optimal decontamination method for individual N95 respirators when reuse is necessary."