Design and Evaluation of a Personal Diffusion Battery.

Area of Science:

• Aerosol Science and Technology
• Environmental Monitoring
• Particle Physics

Background:

• Accurate measurement of submicron particle size distributions is crucial for understanding aerosol behavior and health impacts.
• Existing methods for personal aerosol monitoring can be complex and expensive.
• Diffusion batteries offer a potential method for size-segregating particles.

Purpose of the Study:

• To design and evaluate a four-stage personal diffusion battery (pDB) for measuring submicron particle size distributions.
• To develop a data inversion method for calculating particle size distribution parameters using the pDB.
• To assess the performance of the pDB combined with a condensation particle counter (pDB+CPC) against a standard instrument.

Main Methods:

• Construction of a four-stage screen-type diffusion battery with electronic control and a solenoid valve system.
• Development of a data inversion spreadsheet incorporating particle losses, screen penetration, and detector efficiency.
• Comparison of particle size distribution parameters (NMD, GSD, number concentration) obtained from pDB+CPC with those from a scanning mobility particle sizer (SMPS).

Main Results:

• The pDB+CPC system, with its inversion spreadsheet, achieved measurements within 25% of SMPS for 5 out of 12 polydisperse combustion aerosols.
• The system successfully identified sub-16 nm particle sizes in propylene torch exhaust tests.
• Calculated nanoparticle ratios (R_nano) showed good agreement with reference values when the inversion solved directly, but wider variations occurred when constraints were met.

Conclusions:

• The developed four-stage pDB, when coupled with a CPC and inversion spreadsheet, provides a viable method for measuring submicron particle size distributions.
• The pDB+CPC system demonstrates potential for aerosol characterization, particularly for identifying nanoparticle fractions.
• While the current pDB+CPC has limitations as a personal monitor, modifications with alternative detectors could enhance its personal monitoring capabilities.