Mining Contract: PDM3700-Compatible Filter Module Usable with Portable/Field-deployable Silica Monitoring Instruments

Contract # 75D30121C11931
Start Date 9/1/2021
Research Concept

Exposure to respirable crystalline silica (RCS) in mines poses significant dangers to mine workers, potentially leading to severe health conditions (e.g., silicosis) which oftentimes are fatal. Presently, monitoring of RCS in mines is done by on-site collection of dust particles on samples (filters) followed by off-site analysis by laboratories. Results are only available typically after days or weeks. Thus, for years there has been a push to develop on-site analysis techniques that could provide results more quickly—e.g., near-real time or end-of-shift (EoS)—allowing mines to respond more quickly to elevated exposures.

Contract Status & Impact

This contract is ongoing. For more information on this contract, send a request to

Under this contract, researchers will develop a filter module that can be used with the PDM3700, maintaining that instrument’s functionality of aerosol collection and mass measurement, and portable FTIRs that can be used for NIOSH’s field-deployable silica monitoring technique. Thermo Fisher Scientific will develop a filter medium, hereafter referred to as a “filter module” since it consists of the filter material, a holder, and possibly additional supporting elements and an adaptor.

The current filter used in the PDM3700 is unsuitable for respirable crystalline determination for the following reasons.

  1. The filter material (borosilicate glass microfibers reinforced with woven glass cloth) is a poor transmitter of infrared radiation (IR) in the wavelength regime in which silica absorbs (transmissivity < 0.01)
  2. The filter holder is constructed in such a way that its material framework would obstruct the IR pathway in the FTIR.
  3. The area on the filter over which the dust is collected may not be compatible with the IR area within the FTIR.

In designing a new filter module, the above issues will be taken into account. Additional issues for a new filter include the following.

  1. There should be an allowance for suitable air flow and pressure drop in the PDM3700 such that the filter material retains its integrity.
  2. Aerosol retention percent during dust collection should be suitably close to 100% (it is presently 99.95% for the TEOM filter).
  3. Dust should remain on the filter during transfer from the PDM3700 to FTIR.
  4. The filter should have sufficient particle loading capability.
  5. There should be a suitably low uptake of unwanted gases, especially water vapor.
  6. The technology should be suitable for scaling up for mass production.

Page last reviewed: February 28, 2023
Page last updated: February 28, 2023