Chemical Engineering March 2022 - 26

Facts At Your Fingertips
Respiratory Protection Equipment Types
Department Editor: Scott Jenkins
C
hemical process industries
(CPI) facilities often present a
number of potential respiratory
hazards, including airborne particles,
toxic chemicals and low-oxygen environments,
that may require the use of
respiratory personal-protective equipment
(PPE). This reference outlines
the major categories for respiratory
protection commonly used in industrial
production settings.
Particulate respirator
Particulate-matter respirators are essentially
mechanical filters and are
often the least expensive respiratory
protection devices. Particulate-matter
respirators are made from nonwoven
polypropylene fibers and are
designed to prevent particles, such
as dust and mist (liquid droplets suspended
in air) from entering breathing
passages. They are not designed to
protect against chemicals, gases or
vapors, and are intended only for lowhazard
levels.
Within regulations to certify the
selection and use of
air-purifying
particulate respirators, the National
Institute of Occupational Safety and
Health (part of the U.S. Centers for
Disease Control and Prevention;
www.cdc.gov/niosh) has established
three designations for filter efficiency
and three categories for filter efficiency
degradation. The filter efficiency
refers to the percentage of particles
greater than a given size that are removed
from air. The designations are
95%, 99% and 99.97%.
A commonly known particulatematter
filter is the N95 filtering facepiece
respirator (Figure 1). N95 masks
are so-called because they remove
95% of airborne particles 0.3-microns
and larger in size. Some N95
masks have a valve to reduce breathing
resistance during exhalation. The
" N " refers to the mask's resistance to
oil. N stands for " not resistant to oil. "
The other two categories are R (resistant
to oil) and P (oil-proof).
Chemical cartridge respirator
Chemical cartridge respirators (gas
masks) use replaceable chemical cartridges
or canisters to remove hazardous
gas and vapor contaminants
from the air. This type of respirator
can be a half-mask (Figure 2; nose
and mouth covered), or a facepiece
(covers eyes also) that are secured
to the head with straps. Air passes
through a cartridge or canister, which
filters hazardous gases and vapors
from air by various means, including
absorption, adsorption and chemisorption,
depending on the type of
substance being removed. Chemical
cartridges may also have a filter for
solids as well.
Gas masks are effective only if
used with the correct cartridge or filter
(these terms are often used interchangeably)
for a particular biological
or chemical substance. Cartridges
are available that protect against
more than one hazard, but there is
no " all-in-one " cartridge that protects
against all substances.
A color-code scheme is used to
aid in selection. For example, a canister
coded white is
designed for acid gas,
while a green code
means the canister is
for ammonia. Other color
designations include
blue (carbon monoxide),
black (organic vapors)
and purple (radioactive
materials).
FIGURE 1. Particulate respirators, like the N95 mask shown here, are
made from non-woven polymer fibers
26
Powered respirators
Powered air-purifying
respirators (PAPRs) use
a battery-powered fan
FIGURE 2. Chemical cartridges remove hazardous
gases and vapors from breathed air
to draw air through the filter to the
user's nose and mouth. They consist
of some type of headgear (either
a facemask or a hood), as well as a
motor-driven fan that forces ambient
air into the device, and some
type of filter to remove contaminants
from the air before it reaches the
mouth and nose. PAPRs are easier to
breathe through than gas masks and
nonwoven fiber masks, but they require
a fully charged battery to work
properly. They use the same type of
filters/cartridges as other air-purifying
respirators, so it is equally essential
to know which hazards are present,
and at what concentration, in order to
select the proper type of cartridges.
Self-contained breathing
Self-contained breathing
apparatus
(SCBA) systems use a dedicated air
tank to supply clean air to the user, so
no filters are required. This type of respiratory
protection is capable of protecting
against higher concentrations
of dangerous chemicals. However, a
SCBA system is heavy (30 pounds or
more), and requires special training
on how to use and maintain it. A typical
SCBA air tank lasts about an hour
or possibly less, depending upon the
rating of the SCBA and the breathing
rate and intensity of the user.
n
Resources
OSHA, General Respiratory Protection Guidance for Employers and
Workers, U.S. Occupational Safety and Health Administration, OSHA
Bulletin, 2011.
California Department of Industrial Relations, Respiratory Protection
in the Workplace: A guide for employees, updated April 2021,
accessed online at: www.dir.ca.gov/DOSH/DOSH_Publications/
respiratory-protection-employer-guide.pdf.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
MARCH 2022
http://www.cdc.gov/niosh https://www.dir.ca.gov/DOSH/DOSH_Publications/respiratory-protection-employer-guide.pdf https://www.dir.ca.gov/DOSH/DOSH_Publications/respiratory-protection-employer-guide.pdf http://WWW.CHEMENGONLINE.COM
Chemical Engineering March 2022

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