A PULSED CONDENSATION PARTICLE COUNTER FOR COST EFFECTIVE MONITORING OF ULTRAFINE AIRBORNE PARTICLES

A PULSED CONDENSATION PARTICLE COUNTER FOR COST EFFECTIVE MONITORING OF ULTRAFINE AIRBORNE PARTICLES ABSTRACT This project will develop and validate a new approach for affordably monitoring the number concentration of ultrafine airborne particles. Ultrafine particles are specifically implicated in health, and yet are not detected by lower-cost sensors. Our approach is a Pulsed Condensation Particle Counter that uses adiabatic expansion combined with single particle counting. Our Phase I results demonstrate that this approach is reliable over months of continuous operation, with ±10% agreement with expensive, research-grade condensation particle counters. Our target is an affordable portable instrument, priced at a fraction of the cost of current instruments, that measures the particle number concentration with known accuracy and precision. The envisioned commercial instrument will include a commercial optical counter and report ultrafine particle number concentration and estimated PM2.5 mass. This Phase II project will improve the performance of the Phase I system, refine the supporting components, and integrate the electronics and components into a compact system. The complete prototype system will be tested under both laboratory and field conditions. Instrument precision and accuracy over a range of particle sizes and concentrations will be evaluated with monodispersed, laboratory aerosols, using particle sizes ranging from 5 nm to 2500 nm, and concentrations from near zero to several hundred thousand per cubic centimeter. Instrument robustness will be evaluated through stress-testing at extremes in temperature (5°- 40°C) and humidity (5%-95%). Monitoring performance and stability will be tested through comparison with collocated benchtop instruments over weeks of unattended operation. Measurements under field conditions will be conducted in collaboration with a local university exposure study. Validation as a monitor will be done in collaboration with an air monitoring district. The objective is a compact, cost-effective monitor with a particle detection limit below 5 nm, with precision of ±10% for concentrations between 10 - 104/cm3, and precision of at least ±15% for concentrations reaching 105/cm3, and data recovery of at least 90%.