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Fact
#1
Each style of mask will vary in its ability to provide
adequate protection against pottery related dusts, mists, or
vapors. You will note that each mask listed has a rating that
indicates its limitations. A respirator will provide adequate
protection only up to its limitation.
Fact
#2
Before discussing the limitations of filters and
cartridges, the facepiece limitations must be understood.
Each type of face-piece can be expected to offer a certain amount
of protection; this is called the assigned Protection Factor
(PF). For a disposable, the PF is 5; for a half-mask,
the PF is 10, and for a full face-piece, the PF is 50.
This PF number multiplied by the PEL gives the
maximum concentration the respirator can be used against, as long
as this maximum concentration does not exceed any other limitation
for the cartridge or filter.
Fact
#3
There are two major types of pottery pollutants: Vapors
and Dust/Mist:
a) Cartridges are used to provide
protection against vapors. A cartridge will not provide
protection against dusts or mists.
b) A Filter is used to provide
protection against dusts or mists. A filter will not provide
protection against vapors.
Note:
If you require protection against vapors and dust/mist
simultaneously, you must use a vapor cartridge plus a dust/mist
pre-filter.
Fact
#4
When selecting a respirator for dust protection, there
are two factors to be considered: the PEL for the dust and its
airborne concentration. The PEL is used to determine which type of
filter is required. Filters are approved for dusts/mists either
having a PEL above 0.05 mg/cubic meter, or having a PEL
equal or less than 0.05 mg/cubic meter. The dust concentration
will dictate the type of face-piece to be used, as indicated in
Fact #2.
Example:
The PEL for crystalline cristobalite silica dust is
0.05 mg/cubic meter. Since the PEL is at 0.05 mg/cubic meter, the
filter that is approved for concentration equal to or less than
0.05 mg/cubic meter (The HEPA Filter) is used. The maximum
exposure concentration for this application when using a half-
mask respirator is: Protection Factor multiplied by the PEL, or a
PF of 10 x 0.05 mg/cubic meter = 0.5 mg/cubic meter. |
Fact
#5
Selection of a respirator for protection against gasses
and vapors is much more complicated than for dusts. In addition to
knowing the PEL and the Exposure Concentration of the substance,
the limitation of the chemical cartridge and the presence of good
warning properties (of the substance) must be known. While the
maximum use concentration may still be the PF multiplied by the
PEL, it is possible that some other limitation could be less than
this. Also, if the substance does not have good warning properties
(odor) a chemical cartridge cannot be used, For these reasons be
sure to contact the respirator manufacturer for a specific
recommendation.
Fact
#6
So, which mask do I use? First, you will have to
research the materials you use. Obtain the MSDS for each material
and determine the Permissible Exposure Level (PEL).
Materials that have a PEL
equal to or lower than 0.05 mg/cu. meter will require the HEPA
Dual Cartridge Mask. Of course, the exposure should never exceed
10 times the PEL.
Materials with a PEL
greater than 0.05 mg/cu. meter give you the option of either a
disposable or dual cartridge mask. However, you still have yet to
consider the Actual exposure concentration in your work
environment. Unfortunately, unless you have access to air
sampling, this will be impossible to determine. Carefully
speaking, the disposable masks are only applicable for light dust
concentrations (5 times the PEL) and a dual cartridge should be
used in medium dust concentrations (10 times the PEL). It is the
responsibility of the user to exercise good judgment based on the
PEL of the materials and the working conditions.
If you have any
questions about specific applications, please contact us for
further information.
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