A Carrier for Quantitative Shipment of Coarse Particle Filter Samples

Concern for the potential health effects of inhaled particulates led to a federal standard governing coarse particles, or PM10, for particles below 10 ¿m and subsequently to a fine particle (PM2.5) standard in 1997, for particles below 2.5 ¿m. The U.S. Environmental Protection Agency (EPA) retained the PM10 standard because all particles below 10 ¿m can penetrate into the pulmonary region. Because of the overlap between these two standards, EPA currently is conducting research that could lead to an independent coarse particle standard, which would cover the size range from 2.5 ¿m to 10 ¿m. Coarse particle filters require analyses by gravimetry and chemistry. Inherent with this sampling method is the need for transporting filters from field sites to centralized laboratory facilities for analyses. Substantial particle losses during transport have been documented, and the adoption of a coarse particulate standard will increase concern over this serious source of error. The goal of this Phase I research project is to develop a coarse particle filter transporter, the Electrostatic Particle Clamp, which clamps particles onto the filter by applying a diverging electrostatic field. The electric field induces an electric dipole in each of the particles on the filter while the divergence of that field results in a net force on the particle. With the proper geometry, the resulting electrical force clamps the particles to the filter, reducing or eliminating losses. The exploratory measurements, performed by Aerosol Dynamics, Inc., indicate the feasibility of this approach. It should be emphasized that no charge or any other physical or chemical change is made to the collected particles by this device. Specialized filters are not required, so filter media developed over decades for specialized sampling may be employed. The result of this work will be the development of a coarse particle transport device that will prevent the loss of particles from conventional filters during shipments.