A PULSED CONDENSATION PARTICLE COUNTER FOR
LOW-COST MONITORING OF ULTRAFINE AIRBORNE PARTICLES
ABSTRACT
This project will design, develop and validate a new approach for monitoring the number concentration of
fine and ultrafine airborne particles. Ultrafine particles are specifically implicated in health, and yet are
not detected by currently-used low-cost sensors. Our approach is a Pulsed Condensation Particle
Counter which uses adiabatic expansion combined with single particle counting. With modern optical
sensors, single particle counting is quite feasible, and is more precise than the ensemble measurements
of prior automated adiabatic counters. Our analysis shows that our new method should be much more
energy-efficient than the laminar flow condensation methods now used, as no heating or cooling of the
components is required. Our target is an affordable ($<3000), portable instrument that measures the
particle number concentration with known accuracy and precision, and that bridges the gap in between
the low-cost “citizen science” devices and research-grade instruments.
This Phase I project will assess the feasibility of our concept as a low-cost sensor through modeling and
experiment. It addresses the critical method components, namely system sizing, expansion rate,
humidification and optical detection. Numerical modeling will examine the saturation ratio resulting from
expansion in the presence of heat and water vapor transport from the walls, and how this varies with the
aspect ratio of the expansion volume. This modeling will guide the design of critical components, which
will then be built and tested with laboratory aerosols of known size and composition. The project will
examine cost-efficient means of optical detection of the condensationally enlarged particles, including
coincidence corrections. These components will be tested using existing electronics, and these
experimental data will provide a basis for estimating the accuracy, precision, size, weight, power use and
cost of a fully packaged system.
