In developing countries, high levels of particle pollution from the use of coal and biomass fuels for household cooking and heating are a major cause of ill health and premature mortality. The cost and complexity of existing monitoring equipment, combined with the need to sample many locations, make routine quantification of household particle pollution levels difficult. Recent advances in technology, however, have enabled the development of a small, portable, data-logging particle monitor modified from commercial smoke alarm technology that can meet the needs of surveys in the developing world at reasonable cost. Laboratory comparisons of a prototype particle monitor developed at the University of California at Berkeley (UCB) with gravimetric filters, a tapered element oscillating microbalance, and a TSI DustTrak to quantify the UCB particle monitor response as a function of both concentration and particle size and to examine sensor response in relation to changes in temperature, relative humidity, and elevation are presented here. UCB particle monitors showed good linearity in response to different concentrations of laboratory-generated oleic acid aerosols with a coarse (mass median diameter, 2.1 m) and fine (mass median diameter, 0.27-0.42 m) size distributions (average r 2 ϭ 0.997 Ϯ 0.005). The photoelectric and ionization chamber showed a wide range of responses based on particle size and, thus, require calibration with the aerosol of interest. The ionization chamber was five times more sensitive to fine rather than coarse particles, whereas the photoelectric chamber was five times more sensitive to coarse than fine. The ratio of the response between the two sensors has the potential for mass calibration of individual data points based on estimated parameters of the size distribution. The results demonstrate the significant potential of this monitor, which will facilitate the evaluation of interventions (improved fuels, stoves, and ventilation) on indoor air pollution levels and research on the impacts of indoor particle levels on health in developing countries.

Over the last 20 years, the Kirk R. Smith research group at the University of California Berkeley—in collaboration with Electronically Monitored Ecosystems, Berkeley Air Monitoring Group, and other academic institutions—has developed a suite of relatively inexpensive, rugged, battery-operated, microchip-based devices to quantify parameters related to household air pollution. These devices include two generations of particle monitors; data-logging temperature sensors to assess time of use of household energy devices; a time-activity monitoring system using ultrasound; and a CO2-based tracer-decay system to assess ventilation rates. Development of each system involved numerous iterations of custom hardware, software, and data processing and visualization routines along with both lab and field validation. The devices have been used in hundreds of studies globally and have greatly enhanced our understanding of heterogeneous household air pollution (HAP) concentrations and exposures and factors influencing them.

This article describes a simple combination ionization chamber and angular scattering sensor and presents the results oflaboratory experiments to define its response to micrometer and submicrometer aerosols as a function of aerosol mass, surface, and diameter. The results of these experiments indicate that a simple theory is adequate to describe the operation of the sensor and presents correlations and techniques that will allow the sensor to be used for measurement and characterization of aerosols over a broad spectrum of possible applications related to ad verse environmental and health consequences. For particles with volume mean diameters in the range of ,...., 150-500 nm, the measured sensor respon ses yielded signal-to-noi se ratios in the range of ,....,25 to > 500 for mass concentrations in the range of 0.50 to 16 mg/nr', INTRODUCTIONMeasurement of micrometer (a few j1m) and submicro meter « 1.0 j1m) aerosol properties such as mass conce ntration, surface area, and diam eter are important in understandin g adverse health effects resultin g from human exposure to aerosols. Curr entl y available techniques and instrum entation necessary to conduct such measurement s are gen erally complex, expensive, and often time-consuming to perform. Such instrum ents and techniques are used routinely in developed co untries in mobile Fundi ng by the Hou sehold Energy and Health Programme of the Shell Foundatio n, UK, to deve lop a low-cost particle mon itor for use in deve lop ing co untries is gratefully acknow ledge d. Commen ts on an earlier draft by Michael Apte, Asho k Gadgil , and Edward (Ted) Ze llers are much apprecia ted.Address co rresponde nce to C harles D. Litto n, Pitt sbu rgh Research Laborator y, NIOS H, C DC, P.O . Box 1807 0, Coc hra ns Mill Rd., Pittsbu rgh , PA 15236, USA . E-mai l: chI3@cdc.gov 1054 laboratorie s and ambient-air mon itoring stations and are wellsuitedfor measurements under controlled laboratory conditions. However, their routine use in real-world environments where better measurements of human exposure rather than ambientair monitoring are needed in order to quantify adverse health effects is often difficult, if not impossible. To add to this difficulty, most applications require multiple measurements using several instruments over extended time periods. In some field measurement s, location s may be remote and electrical power unavailable, so that use of these instrum ent s is not possible. Of particul ar intere st to us in this regard are monitors for use in developin g countries to measure part icle levels in and around household s using solid fuels (bio mass and coa l). Such fuels are co mmonly used for coo king and heating, often resulting in high hum an exposure to part icles and apparen tly contributing significantly to premature mortality and illness (Smi th and Mehta 2003).As particle co ncentrations are much higher in the developing world than average levels in developed countries, the risk attributable to particl es fro m indoor and outdoo r co mbustion of solid fuels is...

A series of experiments were conducted to quantify and characterize the optical and physical properties of combustion-generated aerosols during both flaming and smoldering combustion of three materials common to underground mines—Pittsburgh Seam coal, Styrene Butadiene Rubber (a common mine conveyor belt material), and Douglas-fir wood—using a combination of analytical and gravimetric measurements. Laser photometers were utilized in the experiments for continuous measurement of aerosol mass concentrations and for comparison to measurements made using gravimetric filter samples. The aerosols of interest lie in the size range of tens to a few hundred nanometers, out of range of the standard photometer calibration. To correct for these uncertainties, the photometer mass concentrations were compared to gravimetric samples to determine if consistent correlations existed. The response of a calibrated and modified combination ionization/photoelectric smoke detector was also used. In addition, the responses of this sensor and a similar, prototype ionization/photoelectric sensor, along with discrete angular scattering, total scattering, and total extinction measurements, were used to define in real time the size, morphology, and radiative transfer properties of these differing aerosols that are generally in the form of fractal aggregates. SEM/TEM images were also obtained in order to compare qualitatively the real-time, continuous experimental measurements with the visual microscopic measurements. These data clearly show that significant differences exist between aerosols from flaming and from smoldering combustion and that these differences produce very different scattering and absorption signatures. The data also indicate that ionization/photoelectric sensors can be utilized to measure continuously and in real time aerosol properties over a broad spectrum of applications related to adverse environmental and health effects.