2
using personal protected devices (PPE) is the last barrier to
protection against hazards [7]. Ideally, all these measures
should be implemented simultaneously.
Powered Air Purifying respirators (PAPRs) are a type
of respirator that uses a battery and a blower to force air
through a High-Efficiency Particulate Air (HEPA) filter and
deliver clean breathable air to the user [8]. The principal
advantage of these respirators is that they provide signifi-
cantly better protection than the regular respirators com-
monly used in industry. HEPA filters are rated as ‘P100’,
meaning they offer 99.97% filtration efficiency against air-
borne particles and are oil-resistant [9].
The basic components of a PAPR are the face mask, the
blower, and the filters. PAPRs are classified into different
categories based on the type of mask used. The two prin-
cipal categories are tight-fitting and loose-fitting. Tight-
fitting PAPRs provide a full seal between the wearer’s face
and the mask and provide better protection, as leakage is
less likely to happen. However, these respirators need a fit
test to ensure they fit well for each wearer. On the other
hand, loose-fitting PAPRs do not need a fit test and pro-
vide protection using positive pressure to prevent leakage.
These types of respirators can be used along with facial hair
without affecting the fitting. Figure 2 shows both types of
PAPRs. The mask design may vary depending on the model
used, ranging from full to half-face masks in tight-fitting
models, and from helmets to blouses, in loose-fitting ones.
PROTECTION FACTORS
Respirator’s efficiency of protection from particulates is the
most important factor that determines their specific appli-
cation. The most common way to understand and compare
respirators is based on the protection factor (PF), which
is the ratio of the concentration of a certain contaminant
outside the respirator (Co) and the concentration inside of
it (Ci). The mathematical definition of the PF is presented
in Eq. 1.
PF C
C
i
o =(1)
Depending on the conditions under which the PAPR
was tested, different PFs can be defined. However, all of
them are calculated the same way. Definitions for the prin-
cipal protection factors are given below:
a. Assigned Protection Factor (APF): This is the
most general protection factor. It is defined by the
Occupational Safety and Health Administration
(OSHA) as the expected PF when the respirator is
used correctly. This assumes that the respirator does
not have any defects and that it is being used accord-
ing to the provided instructions [10]. Tight-fitting
PAPRs have a higher APF than the loose-fitting ones.
However, these may not be suitable for workers who
cannot pass a fitting test due to facial hair.
b. Workplace Protection Factor (WPF): When the
factor is measured under the specific conditions in
which the respirator is used, it is called the ‘Workplace
Protection Factor’. This allows companies to under-
stand the expected protection under their unique
operating conditions [11].
c. Fit Factor (FF): This protection factor is measured
for a specific individual. It is used to obtain the APF,
the minimum FF experienced by 95% of the users
[11]. The protection factor of some commercially
available PAPRs is shown in Table 2.
P100 filters, like the ones used in PAPRs, have also been
compared to other filters. They show a higher filtration effi-
ciency, as fewer particles can penetrate them. Table 3 com-
pares P100 filters with N95, FFP2, and FFP3 filters.
The filters are named according to the respective stan-
dards and filtration efficiency. The N95 filter has 95%
Figure 2. Loose-fitting helmet (left) and tight-fitting full-face
mask (right)
Table 2. Commercially available PAPRs and their protection
factors [12]
PAPR Filter PF
3M Airstream 060-23-11PAUS (P2 rated*) 50
Drager X-plore 8000 AR HE-F001 (P3 rated†) 100
CleanSpace 2 PAF-0037 (P3 rated†) 100
*Allows 1.0% particle penetration
† Allows 0.05% particle penetration
Table 3. Filtration efficiency comparison [13]
Respirator Class N95 FFP2 FFP3 P100
Mean particle
Penetration [%]
0.634 0.388 0.012 0.013
Standard deviation 0.363 0.186 0.008 0.019
using personal protected devices (PPE) is the last barrier to
protection against hazards [7]. Ideally, all these measures
should be implemented simultaneously.
Powered Air Purifying respirators (PAPRs) are a type
of respirator that uses a battery and a blower to force air
through a High-Efficiency Particulate Air (HEPA) filter and
deliver clean breathable air to the user [8]. The principal
advantage of these respirators is that they provide signifi-
cantly better protection than the regular respirators com-
monly used in industry. HEPA filters are rated as ‘P100’,
meaning they offer 99.97% filtration efficiency against air-
borne particles and are oil-resistant [9].
The basic components of a PAPR are the face mask, the
blower, and the filters. PAPRs are classified into different
categories based on the type of mask used. The two prin-
cipal categories are tight-fitting and loose-fitting. Tight-
fitting PAPRs provide a full seal between the wearer’s face
and the mask and provide better protection, as leakage is
less likely to happen. However, these respirators need a fit
test to ensure they fit well for each wearer. On the other
hand, loose-fitting PAPRs do not need a fit test and pro-
vide protection using positive pressure to prevent leakage.
These types of respirators can be used along with facial hair
without affecting the fitting. Figure 2 shows both types of
PAPRs. The mask design may vary depending on the model
used, ranging from full to half-face masks in tight-fitting
models, and from helmets to blouses, in loose-fitting ones.
PROTECTION FACTORS
Respirator’s efficiency of protection from particulates is the
most important factor that determines their specific appli-
cation. The most common way to understand and compare
respirators is based on the protection factor (PF), which
is the ratio of the concentration of a certain contaminant
outside the respirator (Co) and the concentration inside of
it (Ci). The mathematical definition of the PF is presented
in Eq. 1.
PF C
C
i
o =(1)
Depending on the conditions under which the PAPR
was tested, different PFs can be defined. However, all of
them are calculated the same way. Definitions for the prin-
cipal protection factors are given below:
a. Assigned Protection Factor (APF): This is the
most general protection factor. It is defined by the
Occupational Safety and Health Administration
(OSHA) as the expected PF when the respirator is
used correctly. This assumes that the respirator does
not have any defects and that it is being used accord-
ing to the provided instructions [10]. Tight-fitting
PAPRs have a higher APF than the loose-fitting ones.
However, these may not be suitable for workers who
cannot pass a fitting test due to facial hair.
b. Workplace Protection Factor (WPF): When the
factor is measured under the specific conditions in
which the respirator is used, it is called the ‘Workplace
Protection Factor’. This allows companies to under-
stand the expected protection under their unique
operating conditions [11].
c. Fit Factor (FF): This protection factor is measured
for a specific individual. It is used to obtain the APF,
the minimum FF experienced by 95% of the users
[11]. The protection factor of some commercially
available PAPRs is shown in Table 2.
P100 filters, like the ones used in PAPRs, have also been
compared to other filters. They show a higher filtration effi-
ciency, as fewer particles can penetrate them. Table 3 com-
pares P100 filters with N95, FFP2, and FFP3 filters.
The filters are named according to the respective stan-
dards and filtration efficiency. The N95 filter has 95%
Figure 2. Loose-fitting helmet (left) and tight-fitting full-face
mask (right)
Table 2. Commercially available PAPRs and their protection
factors [12]
PAPR Filter PF
3M Airstream 060-23-11PAUS (P2 rated*) 50
Drager X-plore 8000 AR HE-F001 (P3 rated†) 100
CleanSpace 2 PAF-0037 (P3 rated†) 100
*Allows 1.0% particle penetration
† Allows 0.05% particle penetration
Table 3. Filtration efficiency comparison [13]
Respirator Class N95 FFP2 FFP3 P100
Mean particle
Penetration [%]
0.634 0.388 0.012 0.013
Standard deviation 0.363 0.186 0.008 0.019