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| An N95 respirator
for industrial use. |
N95 Face Masks
An N95 mask or N95 respirator is a particulate-filtering
facepiece respirator that meets the N95 standard of the
U.S. National Institute for Occupational Safety and
Health (NIOSH) air filtration rating, meaning that it
filters at least 95% of airborne particles, while not
resistant to oil like the P95. It is the most common
particulate-filtering facepiece respirator. This kind of
respirator protects against particulates, but not gases
or vapors.
N95 respirators are considered functionally equivalent
to certain respirators regulated under non-U.S.
jurisdictions, such as FFP2 respirators of the European
Union and KN95 respirators of China. However, slightly
different criteria are used to certify their
performance, such as the filter efficiency, test agent
and flow rate, and permissible pressure drop.
The N95 mask requires a fine mesh of synthetic polymer
fibers, also known as nonwoven polypropylene fabric,
which is produced through a highly specialized process
called melt blowing that forms the inner filtration
layer that filters out hazardous particles. |
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Usage
In the United States, the Occupational Safety and Health
Administration (OSHA) requires healthcare workers who
are expected to perform patient activities with those
suspected or confirmed to be infected with COVID-19 to
wear respiratory protection, such as an N95 respirator.
Unlike a respirator, a surgical mask does not have an
air-tight seal and thus does not protect its wearer
against airborne particles such as virus material.
Fit testing is a critical component to a respiratory
protection program whenever workers use tight-fitting
respirators. OSHA requires an initial respirator fit
test to identify the right model, style, and size
respirator for each worker, as well as annual fit tests.
Additionally, tight-fitting respirators, including N95s,
require a user seal check each time one is put on.
Use during shortages
Under serious outbreak conditions in which respirator
supplies are severely limited, workers should work with
their employer to choose the respirator that fits best,
as, even without fit testing, a respirator will provide
better protection than a surgical mask or no mask. In
this case, best practices include trying different
models or sizes to get a good face seal, checking
manufacturer training videos and literature on proper
donning and doffing, doing a user seal check several
times, and checking the fit in a mirror or asking a
colleague to look to be sure the respirator is touching
the face.
During crisis situations where there is a shortage of
N95 respirators, such as the 2019–20 coronavirus
pandemic, the U.S. Centers for Disease Control and
Prevention (CDC) has recommended strategies for
optimizing their use in healthcare settings. N95
respirators can be used beyond their
manufacturer-designated shelf life, although components
such as the straps and nose bridge material may degrade,
which can affect the quality of the fit and seal, making
it particularly important that the wearer perform the
expected seal check. Respirators can be used that are
approved under standards used in other countries that
are similar to NIOSH-approved N95 respirators, including
FFP2 and FFP3 respirators regulated by the European
Union. N95 respirators can be reused a limited number of
times after being removed, as long as they have not been
used during aerosol-generating procedures and are not
contaminated with patients' bodily fluids, although this
increases the risk of surface contamination with
pathogens. The respirator manufacturer may recommend a
maximum number of donnings or uses; if no manufacturer
guidance is available, preliminary data suggests
limiting to five uses per device to ensure an adequate
safety margin.
When it is no longer possible for all healthcare workers
to wear N95 respirators when caring for a COVID-19
patient, respirators should be prioritized for workers
performing aerosol-generating procedures on symptomatic
persons and those within three feet of an unmasked
symptomatic person. Under these conditions, masking of
symptomatic patients with a surgical mask and
maintaining distance from the patient are particularly
important to reduce the risk of transmission. When no
respirators are left, workers who are at higher risk for
severe illness may be excluded from caring for patients,
and workers who have clinically recovered from COVID-19
may be preferred to care for patients. Portable fans
with HEPA filters may also be used to increase
ventilation in isolation rooms when surgical masks are
being used in place of respirators. If neither
respirators nor surgical masks are available, as a last
resort, it may be necessary for healthcare workers to
use masks that have never been evaluated or approved by
NIOSH or homemade masks, such as cloth facemasks, though
caution should be exercised when considering this
option.
Given that the global supply of personal protective
equipment (PPE) is insufficient during the pandemic, the
World Health Organization recommends minimizing the need
for PPE through telemedicine, physical barriers such as
clear windows, allowing only those involved in direct
care to enter a room with a COVID-19 patient, using only
the PPE necessary for the specific task, continuing use
of the same respirator without removing it while caring
for multiple patients with the same diagnosis,
monitoring and coordinating the PPE supply chain, and
discouraging the use of masks for asymptomatic
individuals.
There have been efforts to evaluate cleaning methods for
respirators in emergency shortages, although there is
concern that this may reduce filter performance, or
affect mask fit by deforming the mask. Duke University
researchers have published a method for cleaning N95
respirators without damaging them using vaporized
hydrogen peroxide to allow reuse for a limited number of
times. Battelle received an Emergency Use Authorization
from the U.S. Food and Drug Administration to sterilize
N95 masks. OSHA does not currently have any standards
for disinfecting N95 masks. NIOSH recommends that during
shortages N95 respirators may be used up to five times
without cleaning them, as long as aerosol-generating
procedures are not performed, and respirators are not
contaminated with patients' bodily fluids. Contamination
can be reduced by wearing a cleanable face shield over
an N95 respirator, as well as using clean gloves when
donning and seal-checking a used N95 respirator and
discarding the gloves immediately after.
Contrast with surgical mask
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. If worn properly, a surgical mask
is meant to help block large-particle droplets,
splashes, sprays, or splatter that may contain viruses
and bacteria. Surgical masks may also help reduce
exposure of the wearer's saliva and respiratory
secretions to others.
A surgical 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 not provide complete protection
from germs and other contaminants because of the loose
fit between the surface of the face mask and the face.
Collection efficiency of surgical mask filters can range
from less than 10% to nearly 90% for different
manufacturers’ masks when measured using the test
parameters for NIOSH certification. However, a study
found that even for surgical masks with "good" filters,
80–100% of subjects failed an OSHA-accepted qualitative
fit test, and a quantitative test showed 12–25% leakage.
The U.S. Centers for Disease Control and Prevention
recommends surgical masks in procedures where there can
be an aerosol generation from the wearer, if small
aerosols can produce a disease to the patient. The CDC
recommends the use of respirators with at least N95
certification to protect the wearer from inhalation of
infectious particles including Mycobacterium
tuberculosis, Avian influenza, severe acute respiratory
syndrome (SARS), pandemic influenza, and Ebola. Some N95
respirators have been also cleared by the U.S. Food and
Drug Administration as surgical are labeled "Surgical
N95", and provide respiratory protection to the wearer
as well. |
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