Application of powered air purifying respirators (PAPRs)for protection of underground miners from respirable dust

A powered air-purifying respirator (PAPR) is a battery-operated personal protective device that helps shield mine workers from elevated dust concentration in underground mining operations. It uses a blower to force the contaminated air through a high-efficiency particulate air (HEPA) filter and delivers clean air to the miner. Its filtration efficacy, usually expressed in terms of protection factors, is higher than that of traditional respirators. Therefore, when used in conjunction with traditional engineering controls, PAPR can not only reduce the exposure of mine workers to respirable dust, but it can also be instrumental in regulatory compliance efforts. Background Underground mining operations adopt several measures to reduce the exposure of miners to respirable dust. This includes establishing a mine-wide ventilation system, using dust scrubbers and water sprays, and other engineering controls. The hierarchy of controls to alleviate workers exposure underground can be expressed using a framework developed by the National Institute for Occupational Safety and Health (NIOSH). PAPRs are placed at the bottom of this triangular framework and can be extremely effective when used together with other controls. PAPRs are battery-operated devices that use a blower to force dirt-laden air through a HEPA filter toward the miner’s respirable zone (Fig. 1). Dust particles are captured on different layers inside the mask. As this system is positively pressurized, ambient dust cannot be transported inside the mask and inhaled by the miners. In addition, leakage rates are minimal and fall under 0.50 percent. The filtration efficiency of PAPR is defined in terms of protection factors (PFs): (1) The assigned protection factor (APF) is the minimum expected PF presented by the PAPR when a trained user uses a sound unit according to the prescribed method. (2) The workplace protection factor (WPF) presents the degree of protection offered under a certain circumstance in an operation; this allows the company to understand the specific performance for unique contaminants that might be present. (3) Fit factor (FF) shows the PF of a known respirator for a specific user. NIOSH recommends a minimum APF of 25 for any loose-fitting PAPR with a hood or helmet, and 50 for tight-fitting ones [1]. For their excellent PFs, PAPRs have been mainly implemented in healthcare, followed by the coke and mining industries. Mining, in particular, is a highly regulated industry where operators must meet stringent requirements for regulatory compliance. Computer modeling and laboratory testing methodologies, including breathing simulation studies, are routinely used to study PAPR performance. Exposure standards In the United States, NIOSH, the Food and Drug Administration (FDA) and the Occupational Safety and Health Administration (OSHA) are responsible for researching, establishing and regulating the workplace environment. Some of the frequently used exposure standards are summarized in Table 1. Similar standards exist for other materials. The research results also frequently compare the findings to the established standards. Mining industry petitions to use the PAPRs Due to the excellent particulate capture efficacy ofPAPRs, several mine operators have petitioned MSHA to approve their use in specific operations. These petitions were put forward for operations such as San Juan Mine 1 (Westmoreland San Juan Mining LLC), Foidel Creek Mine (Peabody), West Elk Mine (Mountain Coal Co. LLC), Bailey, Harvey, and Enlow Fork mines (Consol Coal Co.), and Bull Mountains Mine No. 1 (Signal Peak Energy LLC). The petitions requested using the TR-800, TR-800 EX and PAF-0060 PAPRs. These were filed under the provisions of the Code of Federal Regulations (CFR 75.500(d), 75.507-1, 75.1002, 75.507-1(a) and others) [5]. Fig. 1 The major components of a power air-purifying respirator (PAPR):(a) the mask provides a controlled breathing volume, (b) the blower enables the movement of contaminated and clean air through the filter, and (c) filter elements that trap the particles; the parts correspond to a CleanSpace PAPR. Conclusions PAPRs are a class of personal respirators that protect miners by capturing dust particles through a high-efficiency filter. These devices capture particles of sizes exceeding 0.3 µm efficiently and have shown good efficiency capturing much smaller particles as well. Their efficiency is quantified in terms of several types of protection factors, depending on their applications. The particulate alleviation efficiency of PAPRs have been demonstrated extensively in healthcare. Large-scale use of PAPRs in underground mines is still not prevalent, although several operators have petitioned MSHA seeking approval to use specific PAPRs in selected operations. Under the MSHA Final Dust Rule, several NIOSH-approved respirators, including PAPRs, will be permitted to be used in underground mines under specific conditions once current litigation has been addressed and the proposed rule published in the Federal Register on July 22, 2025, is promulgated [6,7]. Acknowledgment The authors acknowledge funding from NIOSH under contract No. 75D 30123C 17277. All views and opinions belong exclusively to the authors. Selected references Nicas M, Neuhaus J (2004) Variability in respiratory protection and the assigned protection factor, Occup Environ Hyg 1:99–109 MSHA (2014) Lowering miners’ exposure to respirable coal mine dust, including continuous personal dust monitors OSHA (2019) Permissible exposure limits – Annotated tables CDC-NIOSH (2018) Appendix C González LS, Kumar AR, Arnold B (2025) Powered air purifying respirators (PAPRs) for protection from respirable dust in underground mines Min Metall Explor 42:2743–2759 MSHA (2024) Fact sheet – Respiratory protection for respirable crystalline silica Federal Register (2025) Powered air purifying respirators (PAPRs) in underground mines: Department of Labor, Mine Safety and Health Administration, 30 CFR Parts 57 and 75

Application of powered air purifying respirators (PAPRs)for protection of underground miners from respirable dust

Authored by: Luis Sánchez González, Ashish Ranjan Kumar* and Barbara Arnold

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