2
LITERATURE REVIEW
Little information exists in the literature on CFD modeling
of PAPRs. Section 2.1 provides a summary of PAPR opera-
tions. Section 2.2 describes some of the studies that were
performed using CFD modeling.
PAPR OPERATIONS
A PAPR operates by capturing the dust-laden air from the
vicinity of the user. A typical PAPR has (i) a battery-oper-
ated fan/blower/pump, (ii) a hose connecting the inlet to
the pump, and (iii) a high- efficiency particulate air (HEPA)
filter. The dust-laden air is brought into the system. The
dust particles are trapped on the filter surface to provide
clean air to the user [6]. The efficacy of PAPRs was demon-
strated in several applications. Hospital personnel rely on
HEPA and other filters to alleviate their exposure to minute
micro-organisms that could be disease carriers [7]. Their
efficiency was demonstrated during the coronavirus disease
caused by the SARS-CoV‑2 virus when surveys showed that
85% of healthcare workers in a hospital in Singapore pre-
ferred to use PAPRs instead of regular masks [8]. The per-
formance of the PAPRs to capture the respirable dust
particles is quantified in terms of ‘Protection Factors (PFs).’
The assigned protection factor for a PAPR with a loose- fit-
ting hood or helmet is 25 [9]. Some of the most used PAPRs
are the 3M Versaflo and the CleanSpace EX (Figure 1). In
this paper, we present the results of airflow simulations
using the 3M Versaflo Helmet.
CFD MODELING OF PAPRS
CFD simulations of PAPRs have not been explored broadly.
Very few studies exist in the literature that show the exter-
nal airflow around a PAPR. However, some research shows
the performance of different components of a PAPR sepa-
rately. In one such work, particle transportation inside the
Figure 1. 3M Versaflo (left) and CleanSpace EX (right)
PAPRs
mask was modeled using Open-FOAM software. It showed
that leakage inside the mask increases as the particle size
decreases [10]. Another CFD study showed experimen-
tally validated results in terms of protection factors of up to
10,000 [11]. Pleated filters, such as the HEPA filters used
in the PAPRs, have also been simulated. Some studies have
focussed on finding the correlation between dust accumula-
tion and pressure drop. A study shows that masks tend to
achieve steady-state pressure with unique filter contamina-
tion percentages [12]. Another study shows that the pres-
sure drop increases as dust accumulates in the filter [13].
An increased particle size also causes lower efficiency in the
filter [14]. In summary, there are no studies that present
modeling results using a replica of a PAPR or airflow and
particulate transport around a miner using a PAPR.
SETTING UP THE CFD MODELS
We present results from CFD simulations of airflow and
particle transportation around a miner’s head. We selected
a 3M Versaflow helmet for CFD simulations. For the simu-
lations, we attached the geometry of the 3M Versaflo hel-
met to a human head model. This section will cover the
parameters used to set up the simulations. We performed
steady-state, transient- state, and particle-tracking simula-
tions systematically to demonstrate the PAPR performance
and five unique cases for every simulation by changing the
inlet airflow velocity from 1.0 m/s to 3.0 m/s in increments
of 0.5 m/s. This enables us to understand the impact of air
velocity on particle behavior.
LIDAR SCAN FOR THE GEOMETRY
There are many techniques for 3D scanning, including pho-
togrammetry and Light Detection and Range (LiDAR).
These techniques allow the creation of a point cloud of
the object, which can then be transformed into a faceted
body and, finally, into a solid body. LiDAR was used for
this study. Many modern phones have the technology that
provides very accurate results. An iPhone 12 Pro and the
mobile application KIRI were used to perform the scan.
This can be used for photogrammetry or LiDAR however,
the limited number of photos that the application can pro-
cess significantly affects the results.
The real 3M Versaflow helmet, generated point cloud,
and faceted body are presented in Figure 2. To obtain a
reliable solid body, some adjustments to the geometry were
made to correct any mistakes during the 3D scanning pro-
cess. Once the helmet geometry was ready, it was attached
to a human head model downloaded from the GrabCAD
library. The final geometry that was used is shown in
Figure 3.
LITERATURE REVIEW
Little information exists in the literature on CFD modeling
of PAPRs. Section 2.1 provides a summary of PAPR opera-
tions. Section 2.2 describes some of the studies that were
performed using CFD modeling.
PAPR OPERATIONS
A PAPR operates by capturing the dust-laden air from the
vicinity of the user. A typical PAPR has (i) a battery-oper-
ated fan/blower/pump, (ii) a hose connecting the inlet to
the pump, and (iii) a high- efficiency particulate air (HEPA)
filter. The dust-laden air is brought into the system. The
dust particles are trapped on the filter surface to provide
clean air to the user [6]. The efficacy of PAPRs was demon-
strated in several applications. Hospital personnel rely on
HEPA and other filters to alleviate their exposure to minute
micro-organisms that could be disease carriers [7]. Their
efficiency was demonstrated during the coronavirus disease
caused by the SARS-CoV‑2 virus when surveys showed that
85% of healthcare workers in a hospital in Singapore pre-
ferred to use PAPRs instead of regular masks [8]. The per-
formance of the PAPRs to capture the respirable dust
particles is quantified in terms of ‘Protection Factors (PFs).’
The assigned protection factor for a PAPR with a loose- fit-
ting hood or helmet is 25 [9]. Some of the most used PAPRs
are the 3M Versaflo and the CleanSpace EX (Figure 1). In
this paper, we present the results of airflow simulations
using the 3M Versaflo Helmet.
CFD MODELING OF PAPRS
CFD simulations of PAPRs have not been explored broadly.
Very few studies exist in the literature that show the exter-
nal airflow around a PAPR. However, some research shows
the performance of different components of a PAPR sepa-
rately. In one such work, particle transportation inside the
Figure 1. 3M Versaflo (left) and CleanSpace EX (right)
PAPRs
mask was modeled using Open-FOAM software. It showed
that leakage inside the mask increases as the particle size
decreases [10]. Another CFD study showed experimen-
tally validated results in terms of protection factors of up to
10,000 [11]. Pleated filters, such as the HEPA filters used
in the PAPRs, have also been simulated. Some studies have
focussed on finding the correlation between dust accumula-
tion and pressure drop. A study shows that masks tend to
achieve steady-state pressure with unique filter contamina-
tion percentages [12]. Another study shows that the pres-
sure drop increases as dust accumulates in the filter [13].
An increased particle size also causes lower efficiency in the
filter [14]. In summary, there are no studies that present
modeling results using a replica of a PAPR or airflow and
particulate transport around a miner using a PAPR.
SETTING UP THE CFD MODELS
We present results from CFD simulations of airflow and
particle transportation around a miner’s head. We selected
a 3M Versaflow helmet for CFD simulations. For the simu-
lations, we attached the geometry of the 3M Versaflo hel-
met to a human head model. This section will cover the
parameters used to set up the simulations. We performed
steady-state, transient- state, and particle-tracking simula-
tions systematically to demonstrate the PAPR performance
and five unique cases for every simulation by changing the
inlet airflow velocity from 1.0 m/s to 3.0 m/s in increments
of 0.5 m/s. This enables us to understand the impact of air
velocity on particle behavior.
LIDAR SCAN FOR THE GEOMETRY
There are many techniques for 3D scanning, including pho-
togrammetry and Light Detection and Range (LiDAR).
These techniques allow the creation of a point cloud of
the object, which can then be transformed into a faceted
body and, finally, into a solid body. LiDAR was used for
this study. Many modern phones have the technology that
provides very accurate results. An iPhone 12 Pro and the
mobile application KIRI were used to perform the scan.
This can be used for photogrammetry or LiDAR however,
the limited number of photos that the application can pro-
cess significantly affects the results.
The real 3M Versaflow helmet, generated point cloud,
and faceted body are presented in Figure 2. To obtain a
reliable solid body, some adjustments to the geometry were
made to correct any mistakes during the 3D scanning pro-
cess. Once the helmet geometry was ready, it was attached
to a human head model downloaded from the GrabCAD
library. The final geometry that was used is shown in
Figure 3.