Comparison of coarse coal dust sampling techniques in a laboratory-simulated longwall section

Airborne coal dust generated during mining can deposit and accumulate on mine surfaces, presenting a dust explosion hazard. When assessing dust hazard mitigation strategies for airborne dust reduction, sampling is done in high-velocity ventilation air, which is used to purge the mining face and gallery tunnel. In this environment, the sampler inlet velocity should be matched to the air stream velocity (isokinetic sampling) to prevent oversampling of coarse dust at low sampler-to-air velocity ratios. Low velocity ratios are often encountered when using low flow rate, personal sampling pumps commonly used in underground mines. In this study, with a goal of employing mine-ready equipment, a personal sampler was adapted for area sampling of coarse coal dust in high-velocity ventilation air. This was done by adapting an isokinetic nozzle to the inlet of an Institute of Occupational Medicine (Edinburgh, Scotland) sampling cassette (IOM). Collected dust masses were compared for the modified IOM isokinetic sampler (IOM-MOD), the IOM without the isokinetic nozzle, and a conventional dust sampling cassette without the cyclone on the inlet. All samplers were operated at a flow rate typical of personal sampling pumps: 2 L/min. To ensure differences between collected masses that could be attributed to sampler design and were not influenced by artifacts from dust concentration gradients, relatively uniform and repeatable dust concentrations were demonstrated in the sampling zone of the National Institute for Occupational Safety and Health experimental mine gallery. Consistent with isokinetic theory, greater differences between isokinetic and non-isokinetic sampled masses were found for larger dust volume-size distributions and higher ventilation air velocities. Since isokinetic sampling is conventionally used to determine total dust concentration, and isokinetic sampling made a difference in collected masses, the results suggest when sampling for coarse coal dust the IOM-MOD may improve airborne coarse dust assessments over “off-the-shelf” sampling cassettes.     

Surface sampling for a pesticide in dust and small spills of a solid dye

The aim was to determine whether a published sampling technique for loose soil on hard surfaces achieved acceptable efficiency at surface dust/soil coverages of 10-20 mg/ 100 cm2. The sampler was a cordless personal sampling pump operated at 4.0 L/min connected to a cassette containing a filter, the cassette being also connected to a Tygon sampling probe that was moved manually on the surface to be sampled. Rhodamine 6G dye dust was evaluated at 10 mg/100 cm2 coverage at flow rates of 1.0-4.0 L/min. Two National Institute of Standards and Technology (NIST) standard reference materials (SRMs) were used for pesticide experiments: SRM 2711 Montana Soil, and SRM 1649a Urban Dust. The efficiencies for these SRMs were determined uncoated, and coated with 1300 microg chlorpyrifos/g as a Lorsban 4E emulsifiable concentrate formulation. The 3-pass technique sampled both the pesticide-coated and uncoated dust and soil at >79 percent efficiency and at better than 16 percent coefficient of variation (CV) above 15 mg collected mass. Sampling at 20 mg/100 cm2 coverage lowered the CV to < or = 7.1 percent. The dye was sampled with similar efficiency > or = 1.5 L/min, but the CV for the 3-pass technique was <10 percent at 1.5-2.0 L/min, and <20 percent at 1.5-4.0 L/min. The efficiency for a 5-pass technique for the dye exceeded 90 percent at > 1.5 L/min with CVs < 10 percent at 1.5, 2.0, 2.5, and 3.5 L/min. The weight change of the sampling probe and the cassette must be measured for accurate determination of low surface coverages rather than just the weight change of the filter alone. The method allows use of personal sampling equipment for aerosols to measure low coverages of loose dust, soil, and chemical solids on hard surfaces.     

Field evaluation and comparison of five methods of sampling lead dust on carpets

Five methods of sampling lead-contaminated dust on carpets were evaluated and compared in 33 New Jersey homes of children with elevated blood lead levels. The five sampling methods were (1) wipe, (2) adhesive label, (3) C18 sheet, (4) vacuum, and (5) hand rinse. Samples were collected side by side on the same carpets within the homes. Among the five methods the wipe and vacuum methods showed high percentages of detectable samples, good reproducibility, and significant correlations with other methods. C18 sheets and adhesive labels collected the least quantity of lead dust, with high percentages of undetectable samples. Because of the limited ability of sampling lead on carpets and the relatively high cost for laboratory analysis, C18 sheets or adhesive labels are not considered feasible sampling techniques. The hand rinse method also was not feasible for carpet sampling, because it was difficult to conduct in the field and laboratory, and it was subject to inconsistency and cross contamination. Wipes, which collected lead dust from carpet surfaces, were believed to be the most appropriate method for measuring lead from carpets accessible to children. However, because of the low pickup from carpets, wipes may not be an appropriate measuring tool to assess the levels of total lead contamination in carpets. The authors recommend using surface wipe sampling to measure accessible lead from carpets for exposure assessment, and vacuum sampling to obtain the information on total lead accumulation.     

Effects of separated flow on cotton dust sampling with a vertical elutriator

The vertical elutriator used for cotton dust sampling was examined theoretically and experimentally to determine airflow patterns and particle transport. The theory of diverging channel flow predicts that a separated eddying flow will occur in the elutriator. This calculation disagrees with the laminar flow assumptions used to predict the size sampling characteristic or cutoff of the elutriator. Smoke injection tests verified random local velocity components and clearly showed that the flow is not uniformly upward and laminar. Particle transport tests indicated that unit density spheres as large as 27 micron can reach the sample on the elutriator filter.     

A comparison of performance of two personal sampling heads for cotton dust

Cotton dust sampling for monitoring worker exposure was traditionally performed by work area sampling. A change to an exposure limit based on personal sampling has recently been agreed. The choice of sampling head for personal monitoring exposure was hampered by the use of two different sampling heads in the major epidemiological studies of textile workers which had incorporated personal sampling techniques. The purpose of this study was to compare the results of exposure measurements using these two sampling heads.This study has examined the performance of the two sampling heads, by performing dual sampling on cotton operatives during normal working activities. Each operative included wore two samplers randomly allocated to left or right side. A minimum of 200 minutes of sampling was accepted and the relative concentrations calculated.The IOM total dust sampler produced repeatedly higher measurements than the Manchester head. The ratio overall was 1.33 (95% C.I. 1.20-1.49). The performance was similar across three ranges of dust exposure from low (< 1 mg/m³-ratio 1.28), medium 1–3 mg/m³-ratio 1.43) to high exposure (>3 mg/m³-ratio 1.24).The two heads give reproducibly proportionate dust measurements with approximately 30% greater results obtained with the IOM total dust sampler. Either dust sampling head could be used for worker monitoring and the results adjusted accordingly for reference to the Maximum Exposure Limit.     

Measuring cyclone for the evaluation of dust sampling instruments SPG 10 AND SPG 210

For dust measuring instruments which are used in industrial hygiene-according to standards there were required certain limited controls of the measurements validity. There is, however, no testing tool available, suitable for the applicants, for a gravimetric dust measuring instrument. It is proposed a measuring cyclone for industrial routine, which can be prepared and graduated with little effort. Examinations of the instruments SPG 10 and SPG 210 so far have shown a close dependence between the volume flow and the resistance to flow of the specific dust filter. The volume flow, actually effective for the grain fraction's separation of the airborne dust into certain parts of coarse dust and lung damaging fine dust in the dust precipitator's first stage may be inadmissibly different from the nominal flow. It is therefore proposed in addition to the necessary check of the measuring devices to establish the relation between volume flow and filter covering for every instrument.     

造船厂矽尘总尘与呼尘浓度的关系探讨

为比较中国、美国和德国粉尘采样方法测定的总尘与呼尘浓度比例关系,分析国产与美国、德国产粉尘采样器测定结果的可比性。在某造船厂的铸造车间于呼吸带高度平行采样8 d,测定总尘、呼尘浓度;分别计算总尘与呼尘浓度的比值,分析其影响因素;以方差分析、相关及回归分析对结果进行统计。结果 :(1)采用国产与美国、德国产采样器测得的总尘与呼尘浓度比值进行比较,差异无统计学意义(ANOVA-SNK检验,P>0.05)。(2)国产与美国产粉尘采样器测定的总尘与呼尘比值随着测尘距离增大而增大,但德国产仪器测定结果则反之。(3)总尘与呼尘浓度呈线性相关,只是国产仪器总尘与呼尘相关程度低于德国和美国。提示,国产仪器粉尘采样总尘、呼尘浓度比值与美国及德国的仪器具有可比性。     

从人体剂量-效应关系比较三种铅尘采样方法

利用新研制的既能测尘又有同步测量工人劳动强度的仪器———半面罩呼吸个体滤膜采样仪, 从人体剂量－ 效应关系的角度, 将其与常规的两种滤膜测尘方法进行比较。     

A field comparison of two methods for sampling lead in household dust.

Comparability of dust lead measurements has been a difficult problem due to different sampling and analysis techniques. This paper compares two dust sampling techniques, the U.S. Department of Housing and Urban Development (HUD) dust wipe method and the Lioy, Wainman, Weisel (LWW) sampler. The HUD method specifies using a moist towelette to pick up as much dust as possible in a specified area and estimates total lead loading. The LWW sampler collects the dust on preweighed wetted filter media, and provides greater standardization of the sampling path and pressure applied. LWW samples were analyzed using inductively coupled plasma mass spectronomy (no samples below minimum detection limit), while HUD samples were analyzed using flame atomic absorption (32% of samples below minimum detection limit). A bootstrapping technique was used in the analysis to contend with those HUD samples below the minimum detection limit. Mixed model equations were generated to predict HUD values from LWW results, and to examine the effects of sampling location, time, and method. The results indicate that the two samplers performed similarly under field conditions, although the LWW sampler produced consistently lower lead loading estimates. LWW values that predicted HUD lead clearance values of 100 micrograms/ft2 for floors and 500 micrograms/ft2 for window sills were 72 micrograms/ft2 and 275 micrograms/ft2, respectively. To examine internal reproducibility, duplicate samples were taken using both the HUD and LWW methods. Correlation results within paired samples indicated a statistically significantly higher (p < 0.001) internal reproducibility for lead loading, for the LWW sampler (r = 0.87), than for the HUD method (r = 0.71). Some of the differences appeared to be related to the analytical methods.     

A comparison of sampling techniques for domestic populations of Triatominae.

Six methods of sampling domestic populations of Triatoma infestans (Klug) in Brazil have been studied. The results suggest that where bug densities are low, the Gomez-Nuñez box may be used, but with higher bug densities withdrawal or removal collecting allows a direct estimation of the size of the bug population. The number of samples to be taken in removal collections depends upon the density of the bug population and the degree of accuracy required.     

A field comparison of inhalable and thoracic size selective sampling techniques.

We measured inhalable, thoracic, and so-called "total" wood dust exposure in British Columbia lumber mill workers. Particle-size selective sampling was conducted using the GSP and Seven hole inhalable samplers, the PEM thoracic sampler and the 37-mm closed-face cassette "total" sampler. All measurements were full-shift personal samples, obtained from randomly selected workers. We obtained intersampler comparison data for the following pairs of instruments: GSP and 37-mm sampler; GSP and seven-hole sampler (SHS); and PEM and 37-mm sampler. The intersampler measurement ratios were estimated as: GSP/37-mm sampler = 4.2; GSP/SHS = 1.7; and PEM/37-mm sampler = 1.6. The GSP/37-mm sampler ratio is consistent with previously reported findings, while PEM/37-mm sampler and GSP/SHS ratios were both larger than expected. We found that in all comparisons, the measurement ratio had significant variability that was greatest at low ambient dust concentrations. Although it was not possible to attribute the source of the variability to specific sampler types, we concluded that the GSP sampler might be susceptible to "projectile" particles not normally aspirated, and may be vulnerable to direct aspiration of dust from accidentally contacted surfaces. The PEM was designed for environmental monitoring, and it is possible that it is unsuited to the higher particulate concentrations found in some occupational settings. Disparities among inhalable sampling techniques such as that between GSP and SHS should be investigated further in light of the proposed adoption of the inhalable method as an industrial standard.     

A comparison of self-reported and observational work sampling techniques for measuring time in nursing tasks

OBJECTIVES: To compare self-reported and observational work sampling techniques when applied to ward-based nurses. METHODS: A self-reported work sampling study was undertaken with nine registered nurses in an Australian teaching hospital over 8.5 weeks, followed by an observational work sampling study conducted over 4.5 weeks. Both studies used a random reminder method and a multidimensional work task classification. Field notes were also recorded and analysed. RESULTS: 3910 data points were collected, 667 during the self-report study and 3243 in the observational study. The two techniques yielded significant differences in work patterns of registered nurses. The observational study showed that compared with the self-reported study, patient care (40% versus 33%, P <0.000) and ward-related activities (7% versus 3%; P <0.001) were recorded significantly more frequently, and documentation less frequently (8% versus 19%; P <0.000). Both the techniques generated similar proportions of time spent in breaks (12%), medication tasks (13%) and clinical discussion (15%). The self-report technique was poorly accepted by nursing staff. The observational technique was well accepted and data collection was more effcient. CONCLUSIONS: The self-report work sampling technique is not a reliable method for obtaining an accurate reflection of the work tasks of ward-based nurses. The observational technique was preferred by nurses, and despite concern regarding a potential Hawthorne effect, this was not substantiated.     

Evaluation of a standardized micro-vacuum sampling method for collection of surface dust

A standardized procedure for collecting dust samples from surfaces using a micro-vacuum sampling technique was evaluated. Experiments were carried out to investigate the collection efficiency of the vacuum sampling method described in ASTM Standard D7144, "Standard Practice for Collection of Surface Dust by Micro-Vacuum Sampling for Subsequent Metals Determination." Weighed masses ( approximately 5, approximately 10 and approximately 25 mg) of three NIST Standard Reference Materials (SRMs) were spiked onto surfaces of various substrates. The SRMs used were: (1) Powdered Lead-Based Paint; (2) Urban Particulate Matter; and (3) Trace Elements in Indoor Dust. Twelve different substrate materials were chosen to be representative of surfaces commonly encountered in occupational and/or indoor settings: (1) wood, (2) tile, (3) linoleum, (4) vinyl, (5) industrial carpet, (6) plush carpet, (7,8) concrete block (painted and unpainted), (9) car seat material, (10) denim, (11) steel, and (12) glass. Samples of SRMs originally spiked onto these surfaces were collected using the standardized micro-vacuum sampling procedure. Gravimetric analysis of material collected within preweighed Accucapinserts (housed within the samplers) was used to measure SRM recoveries. Recoveries ranged from 21.6% (+/- 10.4%, 95% confidence limit [CL]) for SRM 1579 from industrial carpet to 59.2% (+/- 11.0%, 95% CL) for SRM 1579 from glass. For most SRM/substrate combinations, recoveries ranged from approximately 25% to approximately 50%; variabilities differed appreciably. In general, SRM recoveries were higher from smooth and hard surfaces and lower from rough and porous surfaces. Material captured within collection nozzles attached to the sampler inlets was also weighed. A significant fraction of SRM originally spiked onto substrate surfaces was captured within collection nozzles. Percentages of SRMs captured within collection nozzles ranged from approximately 13% (+/- 4 - +/- 5%, 95% CLs) for SRMs 1579 and 2583 from industrial carpet to approximately 45% (+/- 7 - +/- 26%, 95% CLs) for SRM 1648 from glass, tile and steel. For some substrates, loose material from the substrate itself (i.e., substrate particles and fibers) was sometimes collected along with the SRM, both within Accucaps as well as collection nozzles. Co-collection of substrate material can bias results and contribute to sampling variability. The results of this work have provided performance data on the standardized micro-vacuum sampling procedure.     

Comparison of measured respirable dust sampler penetration curves with sampling conventions.

Measured sampler penetration curves are presented for British personal cyclone samplers and the MRE 113A static horizontal elutriator in calm air. These curves are compared with previous results for these instruments, and with theoretical models of sampler behaviour. The sampling efficiency of the elutriator when facing a moderate wind is discussed. The penetration curves are assessed by comparison with standard sampling conventions for respirable dust.