OBJECTIVE
Develop a rugged, 3D printable PFAS-free particulate filtration impactor system that readily attaches to a respirator/mask and is suitable for extended wear in military operational environments with high particulate matter levels during aerobic activity.
DESCRIPTION
Warfighters can be deployed in operational environments with high airborne particulate matter (PM) levels; these events lead to a significant risk of developing cardiovascular and pulmonary disease. Adverse health effects, including cardiovascular and pulmonary disease, are well-documented consequences of exposure to high levels of PM with aerodynamic diameters of less than 10 m (PM10) and especially less than 2.5 m (PM2.5). In many deployment environments as well as in training facilities (e.g., indoor firing ranges and shoot houses), military personnel are continually exposed to levels of PM that exceed the military exposure guidelines (MEG).1 These levels can be greatly exaggerated by anthropogenic activity when exposed to lead residue, burn pits, or dust storms. Unfortunately, current particulate filtration technologies are not idealized for extended wear during military operations. A high burden is associated with utilizing current protective gear while participating in high levels of aerobic activity. The primary complaint that limits use of masks and respirators is discomfort caused by breathing resistance. Due to the extreme levels of PM in some deployed settings, there is the recurring issue of clogging, which further increases breathing resistance and wearer burden. Current filtering equipment is single use, which adds an additional logistics burden when masks/filters need to be continually replaced. Furthermore, many current technologies that provide inhalation protection from particulates utilize HEPA/HESPA media, which can contain PFAS materials. With the environmental and long-term health concerns and regulations facing industries, many manufacturers have announced they are moving away from producing PFAS containing materials this shift could result in a breakdown in the supply chain of particulate matter protection without the development of suitable alternatives.
The objective of this effort is to develop a rugged, novel particulate impactor system that can readily be manufactured at the point of need and attached to current respirators, such as the M50 respirator, commercial half-masks, P100-style masks, and/or balaclava masks and be regenerated after use. This particulate impactor system should be able to trap aerosols upon inhalation. After use, filter media should be capable of regeneration via the removal of any captured PM, allowing the filter to be used again. Here, regeneration refers to the removal of trapped particles after use such that all channels are cleared, and regeneration may be achieved by a secondary step such as reversed air flow through the media from compressed air. Additionally, the ideal system should be able to allow high flow volumes with minimal breathing resistance and should be suitable for wear during aerobic activity. It must also be resistant to clogging and not rely on PFAS-containing media. Technologies utilizing the complex geometries that are enabled by additive manufacturing offer a promising solution towards this mission space due to complex geometries such as lattice structures offering filtration mechanisms such as impaction.2 Additionally, additive manufacturing of this technology enables this novel particulate-focused filtration solution to be manufactured in a forward deployed environment. Technologies that meet the performance criteria will be considered; however, priority shall be given to innovative or novel designs with minimal size and weight, adaptable to respirator/filter design, able to be manufactured under contested logistics, fully self-contained, able to regenerate after use, and have minimal to no power requirements.
PHASE I
Develop and demonstrate filtration technology at a swatch maturity that significantly reduces PM10 and PM2.5 levels and is suitable for integration into a wearable device. The technology must be tested using polydisperse aerosol particles from 0.1-10 m at a concentration of 100 mg/m
3
for PM10 and PM2.5, respectively. The polydisperse aerosol should be formed from both liquids and solids. Minimum operating characteristics for the Phase I demonstration is a reduction of solid and oil particulate concentrations by greater than 95%, and a resistance to clogging for 12 hours. Additionally, the demonstration should also include a data package that indicates low breathing resistance at a moderate static flowrate of 85 L/min before and after loading. For a system before exposure to particulates the target pressure drop is less than 5 mmH
2
O for inhalation and less than 3 mmH
2
O for exhalation, and the pressure drop after loading should be less than 2x the initial pressure drop value. At the conclusion of Phase I, 3 swatches that are 5.3'' in diameter (thickness should not exceed 2.5'') should be delivered to the government POC.
PHASE II
To demonstrate the system's ability to regenerate, capture efficiency and pressure drop of the filter technology should be tested over 3 filtration regeneration cycles under the testing conditions outlined in Phase I. The capture efficiency should not decrease more than 5% per cycle, and the pressure drop should not increase by 5% per cycle. Additionally, these tests should be repeated using a higher static flow rate of 150 L/min to simulate high aerobic activity. Under these conditions, the target pressure drop is less than 3 mmH2O for inhalation and less than 2 mmH2O for exhalation, and the pressure drop after loading should be less than 2x. Additionally, a reduction of particulate concentrations by greater than 99% and a resistance to clogging for 24 hours should be demonstrated. The most promising swatch design from these tests should be adapted into a prototype particulate impactor system that is able to be attached to a mask or respirator. Ideally, in the form of a filter module which can interface with a commercially available half-mask respirator. At the conclusion of Phase II, early design and protypes should be developed that demonstrate how the system will integrate into a commercial respirator/mask system, and a minimum of 10 swatches, but preferably up to 25, of similar size to Phase I should be delivered to the government POC.
PHASE III DUAL USE APPLICATIONS
PHASE III: The overall goal of the project is to develop a NIOSH P100 compliant particulate impactor system that has extreme performance characteristics for low breathing resistance, resistance to clogging, and can be regenerated. Any reduction in exposure of particulates by a mask is dependent upon having a product that fits closely to the face and is correctly donned and worn. Consequently, the fit characteristics of the device that is attached to a commercial mask should be tested using the OSHA quantitative fit testing protocol (1910.134 App A), utilizing test participants that fall within cells 4-7 of the NIOSH-NPPTL bivariate test panel.3 To accommodate the recurring daily use of the device, the prototype should be designed to ensure comfortable fitting with minimal facial abrasions. Additionally, the design must be easily serviceable by the user. As a demonstration of user acceptability, external surveys should be conducted on the overall design, integration, and comfort of the system. Finally, a demonstration for a route to commercialization for scaled production as well as integration into forward deployed efforts should be completed.
PHASE III DUAL USE APPLICATIONS: Potential alternative applications include industrial, agriculture, construction, mining, pharmaceutical, healthcare, international, and other commercial respiratory protection uses.
REFERENCES
https://www.osha.gov/sites/default/files/publications/OSHA3772.pdf
Yu, Y.., Zhang, N.., Hoffman, D.., Rastogi, D.., Woodward, I.., Fromen, C. Design and Evaluation of 3D-Printed Lattice Structures as High Flow Rate Aerosol Filters. ACS Appl. Eng. Mater. 2024, 2, 2875-2884. https://doi.org/10.1021/acsaenm.4c00562
https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppA
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