Options for extended use and re-use of N95 masks

Potential options for use and re-use of N95 FFRs

Compiled by Laila Zomorodian, MD

Contact: zomorodianl15@ecu.edu

Mask use considerations:

1. Most FFRs available are authorized by the CDC; even certain stockpiled FFRs have been approved, however there is always potential for additional risk with non-standard use.

● Re-use: using the same N95 for multiple encounters/patients, but donning and doffing between each patient encounter. Not recommended in the case of COVID-19 or where fomite transmission is a concern.

● ⇨ Extended Use: using the same N95 for multiple encounters with different patients, without removing the respirator between patient encounters. Favored over reuse as it involves less touching/risk of contact transmission. Should be ‘limited’ extended use, but CDC gives no strict definition of this limit.

● ⇨ Doubling: wearing a regular facemask over your N95 respirator. Keep the N95 on throughout the day (less wear and tear with fewer on/off changes) and use the regular facemask as a disposable mask. Should be able to do this in addition to Extended Use.

2. All NIOSH-approved Filtering Facepiece Respirators (FFRs) per the March 2 FDA site update; FDA has also authorized using following brands of expired FFRs in the current setting

3. OSHA allows <5% particle penetration using N95

4. Fisher et al detail the most important potential factors to consider: spread via contact transmission; potential for self-inoculation; FFR shortage; potential for secondary exposures; protection provided by FFR use; government policies and regulations; human factors

Decontamination

Methods compiled in a collaborative working group document (summarized in table below) essentially indicate that UVGI is fast and effective, only one 2006 study did not favor it, questioning it's SARS susceptibility, but at an extremely low dose, 134 µW/cm2, using UV lights from a biosafety cabinet.

(Sources below, since we were unable to post the version of the table with the hyperlinks)

The University of Nebraska developed a decontamination procedure protocol for ultraviolet germicidal irradiation (UVGI) use in used N95 respirators, in an effort to extend their existing stockpile. Important supportive facts include:

1. UVGI inactivates a wide range of human pathogens including coronaviruses and other human respiratory viruses, including when these pathogens are on FFRs

2. Single-stranded RNA viruses, such as SARS-CoV-2, are generally inactivated by UVGI exposure of 2-5 mJ/cm2

3. Nebraska's chosen UVGI exposure @ 60 mJ/cm2 exceeds that needed to inactivate SARS-CoV-2 by a wide margin; this dose is also much lower than dose required to affect fit and filtration characteristics of N95 FFRs.

Their procedure includes (summarized)

1. Irradiate used N95 FFRs with UVGI at an exposure of 60 mJ/cm2.

2. Respirators are secured on wires that are strung across a room with two UVGI towers (ClorDiSys UVGI Light System, https://www.clordisys.com/products.php) on either side.

3. These UVGI towers are equipped with eight 254 nm bulbs (routinely used in biosafety cabinets); they produce 200 μw/cm2 at 10 ft, for a dosage of 12 mJ/minute.

4. To protect the operator from UV damage, monitor the delivered UVGI exposure dose with a UVGI meter that can be initiated/monitored from outside the room to verify that desired exposure has been achieved.

5. Ok to decontaminate and reuse the N95 FFRs multiple times until respirator fit is impacted (2-4). Prior to initiating the decontamination program, the walls and ceiling were covered with a UV-reflective coating (https://lumacept.com) with which our group had experience (5).

6. We believe a variety of UV light sources could be used in a similar fashion including UV equipped biosafety or sterilization cabinets or other UV disinfection systems and that this method can be applied to a variety of other critical items such as procedure masks.

The method described is a result of multiple tests, a review of the scientific literature, and incorporation of current institutional practice

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Sources

1. Effect of Electrostatically charged fibers in Masks/Respirators: https://docs.google.com/document/d/1BV--WPkusWvJQ-e4a3_4KSMavzl6-knt6T0ms8oFOHA/edit#heading=h.rpallwxu5mr6

2. Colgate et al (2010) Reusing Face Masks To Prevent Airborne Illnesses. Youtube. https://www.youtube.com/watch?v=PGHMU4iegLE

3. Viscusi et al (2009) Evaluation of Five Decontamination Methods for Filtering Facepiece Respirators, The Annals of Occupational Hygiene, Volume 53, Issue 8, p815–827 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2781738

4. Viscusi et al (2011) Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease. J Occup Environ Hyg. 2011 Jul;8(7):426-36. doi: 10.1080/15459624.2011.585927.

5. CDC (2008)Guideline for Disinfection and Sterilization in Healthcare Facilities; https://www.cdc.gov/infectioncontrol/pdf/guidelines/disinfection-guidelines-H.pdf

6. Kariwa et al (2006) Inactivation of SARS Coronavirus by Means of Povidone-Iodine, Physical Conditions and Chemical Reagents, Dermatology; 212:119–123; https://doi.org/10.1159/000089211

7. Heimbuch et al (2011) A pandemic influenza preparedness study: Use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets; Am J Infect Control 2011;39:e1-9. doi:10.1016/j.ajic.2010.07.004

8. Lindsley et al (2015) Effects of Ultraviolet Germicidal Irradiation (UVGI) on N95 Respirator Filtration Performance and Structural Integrity, Journal of Occupational and Environmental Hygiene, 12:8, 509- 517, DOI: 10.1080/15459624.2015.1018518

9. Lore et al (2012) Effectiveness of Three Decontamination Treatments against Influenza Virus Applied to Filtering Facepiece Respirators, The Annals of Occupational Hygiene, Volume 56, Issue 1, p92–101, https://doi.org/10.1093/annhyg/mer054

10. Mills et al (2018) Ultraviolet germicidal irradiation of influenza-contaminated N95 filtering facepiece respirators. Am J Infect Control, Volume 46, Issue 7, p. E49-e55. https://doi.org/10.1016/j.ajic.2018.02.018

11. Bedell et al (2016). Coronavirus (MERS) testing with Continuous UVC light. Infect Control Hosp Epidemiol 2016;37:598–599. DOI:10.1017/ice.2015.348

12. Lowe et al: N95 Filtering Facemask Respirator Ultraviolet Germicidal Irradiation (UVGI) Process for Decontamination and Reuse. University of Nebraska document.

1. Tseng and Li (2007): Inactivation of Viruses on Surfaces by Ultraviolet Germicidal Irradiation,Journal of Occupational and Environmental Hygiene, 4:6, 400-405, DOI: 10.1080/15459620701329012

2. Lore et al (2012): see above

3. Viscusi et al (2009): see above

4. Lindsley et al (2015): see above

5. Jelden et al (2017) Ultraviolet (UV)-reflective paint with ultraviolet germicidal irradiation (UVGI) improves decontamination of nosocomial bacteria on 19 hospital room surfaces, Journal of Occupational and Environmental Hygiene, 14:6, 456- 460, DOI: 10.1080/15459624.2017.1296231