with water decreased performance by 21 percent.
Sanitizing N95 masks with alcohol similarly reduced
performance by 37 percent and resulted in significant
shrinkage. Ultraviolet germicidal irradiation has been
tested for sanitization of N95 masks, but in 90 percent
of cases, the integrity of the masks was compromised.
Sanitization by bleach or ethylene oxide created significant
risk to mask wearers due to residue left on the mask.”
Carrillo, et al. (2020) report on use of immediate-use
steam sterilization (IUSS) via an autoclave on N95 masks:
“Masks were packed in paper plastic sterilization peel
pouches for IUSS. Masks were photographed and fit
tested prior to IUSS and this testing protocol was repeated
after the IUSS cycle. The 3M 1870 and M3 1870+ masks
retained efficacy in a quantitative fit test. Quantitative fit
tests were performed using the gold standard TSI Por-
taCount Respirator Fit Tester. Five test subjects were used
to begin to account for individual differences between
faces. For each subject, a fit test was performed before
the IUSS cycle to serve as a control value. Fit tests were
performed after three IUSS. In all cases, masks retained
their structural integrity and efficacy.”
The researchers performed the IUSS cycle with a
chemical indicator and a biological indicator for every
autoclave cycle, confirming that no biological or chemical
contamination was present on the masks. If either
indicator failed the IUSS cycle, the authors said the masks
were reprocessed and not placed into the hospital system.
As Carrillo, et al. (2020) observe, “The numbers in
this study are low to prevent removing N95 masks from
clinical settings and to rapidly translate this finding to
the greater clinical community. Follow-up studies will
be conducted with a significantly larger subject pool by
recruiting subjects from the Houston Methodist Hospital
who will be fit tested for their mask each day. Despite
the limitations of this study, the data herein provide a
valid basis for the use of IUSS for N95 masks to prevent
the spread of COVID-19 to healthcare workers.”
In normal times, the Centers for Disease Control
and Prevention (CDC) maintains that disposable
filtering facepiece respirators (FFRs) are not approved for
routine decontamination and reuse as standard of care;
however, it says that FFR decontamination and reuse
may be considered as a crisis-capacity strategy to ensure
continued availability. Based on the available research
at the time, the CDC stated that ultraviolet germicidal
irradiation, vaporous hydrogen peroxide, and moist
heat “showed the most promise as potential methods
to decontaminate FFRs.”
In its guidance, Decontamination and Reuse of
Filtering Facepiece Respirators, the CDC summarizes
research about decontamination of FFRs before reuse,
and reminds us that, “The surfaces of an FFR may become
contaminated while filtering the inhalation air of the
wearer during exposures to pathogen-laden aerosols.
The pathogens on the filter materials of the FFR may
be transferred to the wearer upon contact with the FFR
during activities such as adjusting the FFR, improper
doffing of the FFR, or when performing a user-seal check
Respiratory Protection
101: N95 Respirators
and Surgical Masks
N95
respirators and surgical masks are examples
of personal protective equipment (PPE) that
are used to protect the wearer from airborne particles
and from liquid contaminating the face. The Centers
for Disease Control and Prevention (CDC) National
Institute for Occupational Safety and Health (NIOSH) and
Occupational Safety and Health Administration (OSHA)
also regulate N95 respirators.
It is important to recognize that the optimal way to
prevent airborne transmission is to use a combination
of interventions from across the hierarchy of controls,
not just PPE alone.
Surgical Masks
A surgical mask is a loose-fitting, disposable device
that creates a physical barrier between the mouth and
nose of the wearer and potential contaminants in the
immediate environment. Surgical masks are regulated
under 21 CFR 878.4040. Surgical masks are not to be
shared and may be labeled as surgical, isolation, dental,
or medical procedure masks. They may come with or
without a face shield. These are often referred to as
face masks, although not all face masks are regulated
as surgical masks.
Surgical masks are made in different thicknesses and
with different ability to protect you from contact with
liquids. These properties may also affect how easily
wearers can breathe through the face mask and how
well the surgical mask protects the user.
If worn properly, a surgical mask is meant to help
block large-particle droplets, splashes, sprays, or splatter
that may contain viruses and bacteria, keeping it from
reaching the mouth and nose. Surgical masks may also
help reduce exposure of saliva and respiratory secretions
to others.
While a surgical mask may be effective in blocking
splashes and large-particle droplets, a face mask, by
design, does not filter or block very small particles in
the air that may be transmitted by coughs, sneezes,
or certain medical procedures. Surgical masks also do
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may 2020 • www.healthcarehygienemagazine.com