SBIR-STTR Award

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.

Public Health Relevance Statement:
NARRATIVE Ultrafine particles are ubiquitous in urban air, and are known to be associated with adverse health risks, yet there are no suitable tools for widespread monitoring their concentrations. This project will develop a new, compact and affordable monitor to report the number concentration of these airborne particles. It will fill known needs for community, fence-line, and distributed network monitoring.

Project Terms:
Aerosols; Affect; Air; Cells; Cell Body; Cities; Communities; Electronics; electronic device; Exhibits; Growth; Generalized Growth; Tissue Growth; ontogeny; Health; Heating; Humidity; Industrialization; Laboratories; Methods; Modernization; Optics; optical; Research; Risk; Schools; Testing; Travel; Weight; Ultrafine; Measures; Price; pricing; base; Humidifier; sensor; Area; Phase; Individual; Measurement; tool; instrument; Pulse; Physiologic pulse; Source; System; Cell Volumes; light scattering; particle; Performance; condensation; Physical condensation; particle monitor; particle counter; Devices; Reporting; Modeling; portability; air sampling; Address; Data; Detection; Monitor; NIEHS; National Institute of Environmental Health Sciences; water vapor; cost; designing; design; new approaches; novel approaches; novel strategy; novel strategies; cost efficient; innovate; innovative; innovation; optical sensor; PM0.1; ultrafine particulate matter; ultrafine particle; atmosphere aerosols; atmospheric aerosols; amateur science; amateur scientists; citizen scientists; civic science; crowd science; crowd-sourced science; scientific citizenship; citizen science; experiment; experimental research; experimental study

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%.

Public Health Relevance Statement:
NARRATIVE Ultrafine particles are ubiquitous in urban air and are known to be associated with adverse health risks, yet there are no suitable tools for widespread monitoring of their concentrations. This project will develop a new, compact low-cost monitor to measure the number concentration of these airborne particles. Based on fundamental principles rather than heuristic correlations, this instrument will provide data of known accuracy and precision. It will be suitable for indoor monitoring in schools, offices, care facilities and industrial environments, and will meet many of the needs for distributed network monitoring.

Project Terms:
Aerosols; Air; Alpha Particles; Alpha Particle Radiation; Alpha Radiation; a Particles; Calibration; Communities; Electronics; electronic device; Environment; Floor; Goals; Health; Health care facility; Health Facilities; Healthcare Facility; care facilities; Humidity; Industrialization; Laboratories; Methods; Noise; optical; Optics; Particle Size; Reading; Research; Risk; Schools; Temperature; Testing; Universities; Vacuum; Ultrafine; Measures; Price; pricing; base; sensor; improved; Phase; Individual; Recovery; Measurement; Collaborations; Community Networks; Exposure to; tool; instrument; Pulse; Physiologic pulse; System; particle; Performance; heuristics; condensation; Physical condensation; particle monitor; particle counter; Agreement; Epidemiologic Research; Epidemiologic Studies; Epidemiological Studies; Epidemiology Research; epidemiologic investigation; epidemiology study; Reporting; Sampling; portability; air monitoring; air sampling; extreme temperature; Data; Detection; Validation; Monitor; Process; cost; novel strategies; new approaches; novel approaches; novel strategy; cost effective; Stress Tests; Coupled; innovation; innovate; innovative; optical sensor; ultrafine particle; PM0.1; ultrafine particulate matter; prototype; operation; particle detector; vertex detector; Inhalation; Inhaling; detection limit; Home