Aerosol Photometer Research Articles

Infiltration of Outdoor PM2.5 Pollution into Homes with Evaporative Coolers in Utah County

Global use of energy-inefficient mechanical vapor-compression air conditioning (AC) is increasing dramatically for home cooling. Direct evaporative coolers (EC) offer substantial energy savings, and may provide a sustainable alternative to AC for homes in hot, dry climates. One drawback of ECs is the potential for infiltration of outdoor air pollution into homes. Prior studies on this topic are limited by small sample sizes and a lack of comparison homes. In this study, we used aerosol photometers to sample indoor and outdoor fine particulate matter (PM2.5) from 16 homes with AC and 14 homes with EC in Utah County, Utah (USA) between July 2022 and August 2023. We observed a significantly larger infiltration factor (Fin) of outdoor PM2.5 in EC vs. AC homes (0.39 vs. 0.12, p = 0.026) during summer. Fin significantly increased during a wildfire smoke event that occurred during the study. During the wildfire event, EC homes offered little to no protection from outdoor PM2.5 (Fin = 0.96, 95% confidence interval (CI) 0.85, 1.07), while AC homes offered significant protection (Fin = 0.23, 95% CI 0.15, 0.32). We recommend additional research focused on cooling pad design for the dual benefits of cooling efficiency and particle filtration.

Characterization of Aerosol Deliveries from Combustible Cigarettes, Heated Tobacco Products, and Electronic Nicotine Delivery Systems Using the Vitrocell Ames 48

Introduction: The Vitrocell® Ames 48 whole-aerosol exposure module offers a high-throughput platform for air-agar-interface exposures that mimic human exposure conditions for assessing potential mutagenic activity of a test article. The aim of this study was to characterize the Vitrocell Ames 48 exposure module for assessment of aerosolized tobacco products utilizing multiple dosimetry techniques and nicotine deposition as determined by chemical analysis. Materials and Methods: Characterization was performed using the Vitrocell VC10® smoking machine and three nicotine containing tobacco product test articles: Kentucky Reference cigarettes (3R4F), a commercially available electrically heated tobacco product (eHTP), and an Electronic Nicotine Delivery System (ENDS). The following dosimetry tools were used: Aerosol photometers (using area under curve values, ∑AUC), free glycerol deposition in phosphate-buffered saline (PBS), fluorescence of anhydrous dimethyl sulfoxide (DMSO)-captured smoke particulate matter, and analytical determination of nicotine in PBS and DMSO. Characterization of 3R4F Kentucky Reference cigarettes was examined over a diluting airflow range 8 to 0.5 L/min; eHTP and ENDS were examined over a diluting airflow range of 4 to 0 L/min (undiluted). Results: Results from the dosimetry techniques showed that whole smoke from 3R4F cigarettes and whole aerosol from eHTP and ENDS demonstrated reproducible and consistent delivery, with results being consistent between experiments and within each airflow. Conclusion: These results show that this exposure module is fit for purpose using these three tobacco product types.

Comparison of the Aerosol Photometer and Light Scattering Airborne Particle Counter (LSAPC) Methods for Installed Filter System Leak Testing

Abstract The installed filter system leak test method for cleanrooms and clean zones is described in ISO 14644-3, Cleanrooms and associated controlled environments—Part 3: Test method. Portions of the methods in ISO 14644-3 were adapted from IEST-RP-CC034.4[Schaumburg, Illinois, US: Institute of Environmental Science and Technology], which provides a set of recommended procedures for leak testing HEPA and ULPA filters in situ (in the field) with the aerosol photometer test method and the light scattering airborne particle counter (LSAPC) test method. Leak testing is performed to confirm that the final high efficiency air filter system is properly installed by verifying the absence of bypass leakage in the installation, and that the filters are free of defects (small holes and other damage in the filter medium, frame, seal and leaks in the filter bank framework). This study was conducted to compare the aerosol photometer and LSAPC methods. Testing in the study consisted of creating artificial leaks in the filter system, measuring the upstream and downstream concentrations with the aerosol photometer and with the LSAPC, and comparing the filter leak penetration results. Comparison testing was applied to the procedure for the installed terminal panel filter system leakage scan test (stationary measurement) and the procedure for evaluating overall leakage of high-airflow box-type filters mounted in a duct or air-handling unit (AHU) (overall leakage test). It was found that the aerosol photometer and the LSAPC gave similar results for filter leakage within experimental error. The comparison of the leakage scan tests (stationary measurement) showed that the penetration calculated for the channel ≥ 0.3 μm of the LSAPC with an air flow rate of 1cu ft/min (CFM) (28.3 l/min) was very similar to the penetration measured with the aerosol photometer for a leakage level >0.01 % of the upstream concentration. The comparison result of the overall leakage test showed that overall total penetration values, obtained after dilution of artificial calibrated leaks in the filter media, were identical, within the measurement uncertainty, for particles ≥0.3 μm whether the sampling rate of the LSAPC was 1 CFM (28.3 l/min) or 50 l/min. Several recommendations are provided. In particular, for filters mounted in a duct or AHU where the filter function is critical, the recommended method is the leakage scan test method, using a grid sampling method in a plane downstream of the filter (as agreed between customer and supplier).

Measuring airflow through the portable high-efficiency air filtration (PHEAF) device to assess reliability of instrument and sample location

ABSTRACT The portable high-efficiency air filtration (PHEAF) device is an engineering control common to the environmental remediation industry. Damage to the high-efficiency particulate air (HEPA) filter (e.g., filtration media, gasket), improper installation of the filter into the mounting frame, or defects in the filtration housing affect the capture efficiency of the device. PHEAF devices operating at less than marketed efficiencies justify periodic leak testing of the PHEAF device, especially when the filtered air is exhausted into occupied spaces. A leak test is accomplished by injecting a known concentration of aerosol upstream of the HEPA filter and measuring the percentage of aerosol penetrating through the filtration system. The test protocol scripted for stationary systems (i.e., biological safety cabinets) states that upstream concentrations can be empirically determined using the aerosol photometer to measure particulate matter (PM) in the airstream. This practice requires a homogenous mixture of the aerosol challenge agent within the airstream. However, design of the PHEAF device does not include a validated induction point for the aerosol. Absent of an acceptable means to achieve a homogenous mixture for upstream measurement, the aerosol concentration is mathematically derived based on the measured air volume passing through the PHEAF equipment. In this study, intake volume and exhaust volume for each PHEAF device were measured by either the balometer or the hot wire anemometer. Variability of measurements was examined by instrument and sample location (intake vs. exhaust) to understand which combination would be most consistent for measuring airflow volume. From this study, the authors conclude that the balometer is preferred compared with the hot wire anemometer for measuring airflow through the PHEAF device. Exhaust measurement by balometer seems more reliable than intake measurements by hot wire anemometer. Implications: Although testing of PHEAF devices is recommended by various public health authorities, no nationally recognized test protocol has been published in the United States. In support of measuring the performance of the PHEAF device in a field setting, this study evaluated the hot wire anemometer and balometer techniques and sample locations (intake vs. exhaust) to reliably measure airflow through the PHEAF device. Since accuracy of the particle measurement is associated with airflow volume, it is essential to obtain a true airflow reading. This study suggests that the balometer was more consistent in measuring airflow through the PHEAF device.

Investigation of multiple whole smoke dosimetry techniques using a VITROCELL®VC10® smoke exposure system.

The Vitrocell® VC10® smoke exposure system offers multiple platforms for air liquid interface (ALI) and air agar interface (AAI) exposure that mimic in vivo conditions for assessing toxicological impact of whole smoke using in vitro assays. The aim of this study was to investigate and compare multiple dosimetry techniques that may be employed during combustible cigarette whole smoke exposure using the Vitrocell® VC10® smoking robot. The following techniques were assessed: (1) quartz crystal microbalances (QCMs), (2) aerosol photometers (using area under curve, AUC), and (3) fluorescence of anhydrous dimethyl sulfoxide (DMSO)-captured smoke constituents. Results showed that each of the dosimetry techniques was able to distinguish different levels of whole smoke airflow in a concentration-related manner. When compared to each other, the three techniques showed a high level of consistency and all were considered efficient tools in quantifying dose during an exposure, although higher variation was observed at the higher airflows tested. Overall, the dosimetry tools investigated here provide effective measures of the whole smoke concentrations tested during the exposure.

Capture efficiency of portable high-efficiency air filtration devices used during building construction activities

ABSTRACTThe portable high-efficiency air filtration (PHEAF) device is used to control particulate matter (PM) generated from construction-type activities occurring within the built environment. Examples of activities where PHEAF devices are mobilized include building renovation, asbestos abatement, remediation of microbial contamination, and lead-based paint projects. Designed for use on short-term, temporary projects the PHEAF device captures airborne PM using a high-efficiency particulate air (HEPA) filter. This study sought to evaluate the capture efficiency of the PHEAF device in a field setting. An aerosol generator and photometer were used to measure particle penetration through 85 PHEAF devices. Average overall capture efficiency ranged from 41.78% to ≥99.97% with more than 88% of the tests failing to achieve 99.97% capture efficiency. Approximately 73% of the PHEAF device sample population failed to demonstrate HEPA performance criteria during any test round. A higher occurrence of PM concentrations measured around the perimeter of the filter suggested the presence of bypass leakage. While PHEAF devices were effective in capturing a significant quantity of aerosol test agent, these findings suggest that routine testing of the PHEAF device should be conducted to validate performance.

Evaluation of consumer monitors to measure particulate matter

Recently, inexpensive (<$300) consumer aerosol monitors (CAMs) targeted for use in homes have become available. We evaluated the accuracy, bias, and precision of three CAMs (Foobot from Airoxlab, Speck from Carnegie Mellon University, and AirBeam from HabitatMap) for measuring mass concentrations in occupational settings. In a laboratory study, PM2.5 measured with the CAMs and a medium-cost aerosol photometer (personal DataRAM 1500, Thermo Scientific) were compared to that from reference instruments for three aerosols (salt, welding fume, and Arizona road dust, ARD) at concentrations up to 8500µg/m3. Three of each type of CAM were included to estimate precision. Compared to reference instruments, mass concentrations measured with the Foobot (r-value = 0.99) and medium-cost photometer (r-value=0.99) show strong correlation, whereas those from the Speck (r-value range 0.91-0.99) and AirBeam (0.7–0.96) were less correlated. The Foobot bias was (−12%) for ARD and measurements were similar to the medium-cost instrument. Foobot bias was (<−46%) for salt and welding fume aerosols. Speck bias was at 18% for ARD and −86% for welding fume. AirBeam bias was (−36%) for salt and (−83%) for welding fume. All three photometers had a bias (<−82%) for welding fume. Precision was excellent for the Foobot (coefficient of variation range: 5–8%) and AirBeam (2–9%), but poorer for the Speck (8–25%). These findings suggest that the Foobot, with a linear response to different aerosol types and good precision, can provide reasonable estimates of PM2.5 in the workplace after site-specific calibration to account for particle size and composition.

Inter-comparison of Low-cost Sensors for Measuring the Mass Concentration of Occupational Aerosols.

Low-cost sensors are effective for measuring the mass concentration of ambient aerosols and secondhand smoke in homes, but their use at concentrations relevant to occupational settings has not been demonstrated. We measured the concentrations of four aerosols (salt, Arizona road dust, welding fume, and diesel exhaust) with three types of low-cost sensors (a DC1700 from Dylos and two commodity sensors from Sharp), an aerosol photometer, and reference instruments at concentrations up to 6500 μg/m3. Raw output was used to assess sensor precision and develop equations to compute mass concentrations. EPA and NIOSH protocols were used to assess the mass concentrations estimated with low-cost sensors compared to reference instruments. The detection efficiency of the DC1700 ranged from 0.04% at 0.1 μm to 108% at 5 μm, as expected, although misclassification of fine and coarse particles was observed. The raw output of the DC1700 had higher precision (lower coefficient of variation, CV = 7.4%) than that of the two sharp devices (CV = 25% and 17%), a finding attributed to differences in manufacturer calibration. Aerosol type strongly influenced sensor response, indicating the need for on-site calibration to convert sensor output to mass concentration. Once calibrated, however, the mass concentration estimated with low-cost sensors was highly correlated with that of reference instruments (R2=0.99). These results suggest that the DC1700 and Sharp sensors are useful in estimating aerosol mass concentration for aerosols at concentrations relevant to the workplace.

Evaluation of a Low-Cost Aerosol Sensor to Assess Dust Concentrations in a Swine Building.

Exposure to dust is a known occupational hazard in the swine industry, although efforts to measure exposures are labor intensive and costly. In this study, we evaluated a Dylos DC1100 as a low-cost (~$200) alternative to assess respirable dust concentrations in a swine building in winter. Dust concentrations were measured with collocated monitors (Dylos DC1100; an aerosol photometer, the pDR-1200; and a respirable sampler analyzed gravimetrically) placed in two locations within a swine farrowing building in winter for 18-24-h periods. The particle number concentrations measured with the DC1100 were converted to mass concentration using two methods: Physical Property Method and Regression Method. Raw number concentrations from the DC1100 were highly correlated to mass concentrations measured with the pDR-1200 with a coefficient of determination (R (2)) of 0.85, indicating that the two monitors respond similarly to respirable dust in this environment. Both methods of converting DC1100 number concentrations to mass concentrations yielded strong linear relationships relative to that measured with the pDR-1200 (Physical Property Method: slope = 1.03, R (2) = 0.72; Regression Method: slope = 0.72, R (2) = 0.73) and relative to that measured gravimetrically (Physical Property Method: slope = 1.08, R (2) = 0.64; Regression Method: slope = 0.75, R (2) = 0.62). The DC1100 can be used as a reasonable indicator of respirable mass concentrations within a CAFO and may have broader applicability to other agricultural and industrial settings.

Evaluating the capabilities of portable black carbon monitors and photometers for measuring airborne carbon nanotubes

For daily monitoring of occupational exposure to aerosolized carbon nanotubes (CNTs) where CNTs are manufactured and handled, inexpensive real-time measuring methods are preferable. In this study, we evaluated the capabilities of a portable black carbon monitor (BCM; also called an aethalometer) and a light-scattering aerosol photometer in detecting airborne CNTs. The responses of these instruments to airborne CNTs, aerosolized through vortex shaking, were evaluated by comparing the measurements of CNT mass concentrations made by these instruments to those determined through thermal carbon analysis. Results showed that their raw readings underestimated CNT mass concentrations in most cases. Their sensitivities depended on the type of CNTs and decreased with the particle sizes of aerosolized CNT clumps. We also found that the sensitivity of the BCM tended to substantially decrease with increasing filter load, even before the point at which the filter should be replaced as recommended by the manufacturer, which could be attributed to a clean environmental condition (i.e., the absence of ubiquitous light-scattering material). As an example of the use of these instruments for measuring airborne CNTs in the presence of background aerosols, a CNT-handling simulation was also conducted. Although both the BCM and the photometer could detect CNT emissions, the BCM was more sensitive to the detection of emitted CNTs in the presence of background aerosols. The correction factors obtained from the response evaluations could enhance the measurement accuracy of these instruments, which will be helpful for the daily monitoring of CNTs at workplaces.

Clean Benches

Clean Benches

Optoelectronic system of the aerosol photometer in the detector of molecular condensation nuclei

We study the light scattering by aerosol particles and air in the photometer of the molecular condensation nuclei, as well as the sensitivity of the photodector of the photometer. The interference nature of light scattering by aerosol particles is established and is found to be comparable (in order of magnitude) with the scattering of light by air in the photometer. The sensitivity of the photometer can be increased by more than an order of magnitude due to optimization of the optoelectronic part of the photometer. The detection threshold for the target component of the gas analyzer is attained at the spontaneous ionization background level and not at the limiting sensitivity level of the photodetector.

Distribution of Particle and Gas Concentrations in Swine Gestation Confined Animal Feeding Operations

Dust mass concentrations, temperatures, and carbon dioxide concentrations were mapped in a modern, 1048-pen swine gestation barn in winter, spring, and summer. In each season, two technicians measured respirable mass concentrations with an aerosol photometer and temperatures and carbon dioxide concentrations with an indoor air quality monitor at 60 positions in the barn. Stationary photometers were also deployed to measure mass concentrations during mapping at five fixed locations. In winter when building ventilation rates were low (center-barn mean air velocity=0.34 m s(-1), 68 fpm) to conserve heat within the barn, mass and carbon dioxide concentrations were highest (mass geometric mean, GM=0.50 mg m(-3); CO2 GM=2060 ppm) and fairly uniform over space (mass geometric standard deviation, GSD=1.48; CO2 GSD=1.24). Concentrations were lowest in summer (mass GM=0.13 mg m(-3); CO2 GM=610 ppm) when ventilation rates were high (center-barn mean air velocity=0.99 m s(-1), 196 fpm) to provide cooling. Spatial gradients were greatest in spring (mass GSD=2.11; CO2 GSD=1.50) with low concentrations observed near the building intake, increasing to higher concentrations at the building exhaust. Mass concentrations obtained in mapping were generally consistent with those obtained from stationary monitors. A moderately strong linear relationship (R2=0.60) was observed between the log of photometer-measured mass concentration and the log of carbon dioxide concentration, suggesting that carbon dioxide may be an inexpensive alternative to assessing air quality in a swine barn. These results indicate that ventilation can effectively reduce contaminant levels in addition to controlling temperature.

Concentration and oxidative potential of on-road particle emissions and their relationship with traffic composition: Relevance to exposure assessment

Particles emitted by vehicles are known to cause detrimental health effects, with their size and oxidative potential among the main factors responsible. Therefore, understanding the relationship between traffic composition and both the physical characteristics and oxidative potential of particles is critical. To contribute to the limited knowledge base in this area, we investigated this relationship in a 4.5 km road tunnel in Brisbane, Australia.On-road concentrations of ultrafine particles (<100 nm, UFPs), fine particles (PM2.5), CO, CO2 and particle associated reactive oxygen species (ROS) were measured using vehicle-based mobile sampling. UFPs were measured using a condensation particle counter and PM2.5 with a DustTrak aerosol photometer. A new profluorescent nitroxide probe, BPEAnit, was used to determine ROS levels. Comparative measurements were also performed on an above-ground road to assess the role of emission dilution on the parameters measured.The profile of UFP and PM2.5 concentration with distance through the tunnel was determined, and demonstrated relationships with both road gradient and tunnel ventilation. ROS levels in the tunnel were found to be high compared to an open road with similar traffic characteristics, which was attributed to the substantial difference in estimated emission dilution ratios on the two roadways. Principal component analysis (PCA) revealed that the levels of pollutants and ROS were generally better correlated with total traffic count, rather than the traffic composition (i.e. diesel and gasoline-powered vehicles).A possible reason for the lack of correlation with HDV, which has previously been shown to be strongly associated with UFPs especially, was the low absolute numbers encountered during the sampling. This may have made their contribution to in-tunnel pollution largely indistinguishable from the total vehicle volume. For ROS, the stronger association observed with HDV and gasoline vehicles when combined (total traffic count) compared to when considered individually may signal a role for the interaction of their emissions as a determinant of on-road ROS in this pilot study. If further validated, this should not be overlooked in studies of on- or near-road particle exposure and its potential health effects.

Field Evaluation of an Engineering Control for Respirable Crystalline Silica Exposures During Mortar Removal

During mortar removal with a right angle grinder, a building renovation process known as “tuck pointing,” worker exposures to respirable crystalline silica can be as high as 5 mg/m3, 100 times the recommended exposure limit developed by the National Institute for Occupational Safety and Health. To reduce the risk of silicosis among these workers, a vacuum cleaner can be used to exhaust 80 ft3/min (2.26 m3/min) from a hood mounted on the grinder. Field trials examined the ability of vacuum cleaners to maintain adequate exhaust ventilation rates and measure exposure outcomes when using this engineering control. These field trials involved task-based exposure measurement of respirable dust and crystalline silica exposures during mortar removal. These measurements were compared with published exposure data. Vacuum cleaner airflows were obtained by measuring and digitally logging vacuum cleaner static pressure at the inlet to the vacuum cleaner motor. Static pressures were converted to airflows based on experimentally determined fan curves. In two cases, video exposure monitoring was conducted to study the relationship between worker activities and dust exposure. Worker activities were video taped concurrent with aerosol photometer measurement of dust exposure and vacuum cleaner static pressure as a measure of airflow. During these field trials, respirable crystalline silica exposures for 22 samples had a geometric mean of 0.06 mg/m3 and a range of less than 0.01 to 0.86 mg/m3. For three other studies, respirable crystalline silica exposures during mortar removal have a geometric means of 1.1 to 0.35. Although this field study documented noticeably less exposure to crystalline silica, video exposure monitoring found that the local exhaust ventilation provided incomplete dust control due to low exhaust flow rates, certain work practices, and missing mortar. Vacuum cleaner airflow decrease had a range of 3 to 0.4 ft3/min (0.08 to 0.01 m3/sec2) over a range of vacuum cleaners, hose diameters, and hose lengths. To control worker exposure to respirable crystalline silica, local exhaust ventilation needs to be incorporated into a comprehensive silica control program that includes respiratory protection, worker training, and local exhaust ventilation.

A Comparison of Total, Respirable, and Real-Time Airborne Particulate Sampling in Horse Barns

Measurements of total, respirable, and real-time airborne particulate were obtained in 12 horse barns in summer and winter. Respirable and total particulate concentrations were measured gravimetrically; real-time particulate was measured with an aerosol photometer. Total particulate (TP) ranged from nondetectable (ND) to 2.1 mg/m3 and from ND to 1.2 mg/m3 for winter and summer sampling, respectively. Respirable particulate (RP) ranged from ND to 0.2 mg/m3 and from ND to 0.7 mg/m3 for winter and summer measurements, respectively. The mean respirable fraction of particulate for summer and winter measurements was 0.63 and 0.34, respectively Real-time particulate (RTP) concentration was significantly correlated with TP for winter measurements and for pooled data but was not significantly correlated with RP for winter, summer, or pooled measurements. Peak, 10-sec average levels of RTP were estimated to range up to 22 mg/m3 in the samples collected. The data suggest that (a) airborne particulate concentrations and particle size distributions vary considerably among horse barns, and (b) real-time sampling, with an aerosol photometer, may be a more reliable measure of airborne TP than airborne RP in these environments.

Total respiratory tract deposition of fine micrometer-sized particles in healthy adults: empirical equations for sex and breathing pattern

Accurate dose estimation under various inhalation conditions is important for assessing both the potential health effects of pollutant particles and the therapeutic efficacy of medicinal aerosols. We measured total deposition fraction (TDF) of monodisperse micrometer-sized particles [particle diameter (Dp) = 1, 3, and 5 microm in diameter] in healthy adults (8 men and 7 women) in a wide range of breathing patterns; tidal volumes (Vt) of 350-1500 ml and respiratory flow rates (Q) of 175-1,000 ml/s. The subject inhaled test aerosols for 10-20 breaths with each of the prescribed breathing patterns, and TDF was obtained by monitoring inhaled and exhaled aerosols breath by breath by a laser aerosol photometer. Results show that TDF varied from 0.12-0.25, 0.26-0.68, and 0.45-0.83 for Dp = 1, 3, and 5 microm, respectively, depending on the breathing pattern used. TDF was comparable between men and women for Dp = 1 microm but was greater in women than men for Dp = 3 and 5 microm for all breathing patterns used (P < 0.05). TDF increased with an increase in Vt regardless of Dp and Q used. At a fixed Vt TDF decreased with an increase in Q for Dp = 1 and 3 microm but did not show any significant changes for Dp = 5 microm. The varying TDF values, however, could be consolidated by a single composite parameter (omega) consisting of Dp, Vt, and Q. The results indicate that unifying empirical formulas provide a convenient means of assessing deposition dose of particles under varying inhalation conditions.

Heart Rate Variability and Particulate Exposure in Vehicle Maintenance Workers: A Pilot Study

The association between occupational exposure to PM2.5 and heart rate variability was investigated in a repeated measures, longitudinal study of vehicle maintenance workers occupationally exposed to automobile emissions. Five subjects were monitored for occupational exposure to fine particulate matter (PM2.5) on 6 workdays using an aerosol photometer, validated with side-by-side sampling with a gravimetric method. End-of-day heart rate variability statistics were derived using short-term electrocardiogram recordings for each participant. Workplace carbon monoxide and outdoor, ambient fine particulate matter were also monitored. Regression statistics were used to investigate associations between same-day PM2.5 levels and heart rate variability statistics using mixed-effects multiple regression of pooled data. No statistically significant associations were observed between occupational PM2.5 and measures of heart rate variability. A statistically significant increase in total spectral power was associated with ambient PM2.5 (p < 0.05). The data suggest a threshold below which no degradation in cardiac autonomic control of healthy workers occurs when challenged by occupational PM2.5 exposure. This study was limited in population, exposure level, and type of particulate exposures. Additional studies are recommended on broader occupational populations.

Dynamic monitoring of the dust pickup efficiency of vacuum cleaners.

This study evaluated a new method that uses an optical aerosol photometer for dynamically monitoring dust pickup efficiency during vacuuming. In the first stage of this study the new method was compared with built-in dirt sensors installed by vacuum cleaner manufacturers. Through parallel testing it has been shown that the widely available built-in dirt sensors are not sensitive enough to register small (< 53 microm) dust particles. Therefore, only the optical photometer was used in the rest of the experiments of this study to monitor the dust pickup efficiency while the vacuum cleaner was operated with different nozzles on clean and soiled carpet and vinyl sheet flooring. This method also was used to monitor dust pickup efficiency when vacuuming carpets originating from lead-contaminated homes. The dust pickup efficiencies obtained with the optical aerosol photometer have been compared with the surface lead concentrations found during different stages of cleaning. Results indicate that the dust mass concentration registered with the optical aerosol photometer at the nozzle outlet correlates well with the dust mass collected in the vacuum cleaner filter bag and with the surface lead level. Therefore, dynamic dust pickup monitoring can provide valuable information about the efficiency of cleaning when a vacuum cleaner is used. This suggests that a small aerosol photometer similar to a light-scattering smoke detector would be beneficial in vacuum cleaners used for cleaning surfaces contaminated with leaded dust and biological particles (including allergens).

Aerosol optical properties during the Lindenberg Aerosol Characterization Experiment (LACE 98)

The optical properties of atmospheric aerosol particles were measured close to ground level using different methods at Lindenberg/Falkenberg (Germany) during the Lindenberg Aerosol Characterization Experiment (LACE 98), 13 July 1998 to 14 August 1998 [Ansmann et al., 2002]. The experimental setup consisted of (a) an aerosol photometer, which measured a complete set of aerosol optical properties, such as extinction, scattering, and absorption coefficients, single scattering albedo, apparent complex refractive index, asymmetry parameter of the phase function of scattering, and apparent volume soot content, (b) an integrating plate, which measured the absorption coefficient, and (c) a nephelometer and (d) a particle soot absorption photometer (PSAP) for measurements of scattering and absorption coefficients. All these measurements were performed under dry conditions. A telephotometer and a horizontal lidar were used to determine the aerosol extinction coefficient under ambient conditions. This paper presents a closure study of the different measurement methods. An empirical correction function for the PSAP is introduced and compared with a semiempirical correction function previously introduced by Bond et al. [1999]. A detailed model of humidity effects on the extinction coefficient is presented using “coated sphere” calculations based on measured input values of the size distribution, the chemical composition, the growth factor at 90% relative humidity, the water‐soluble fraction of particulate materials, the temperature, and the relative humidity. Model calculations allowed an intercomparison of measured values of particles in the dry state and at ambient relative humidity and showed good agreement.