Measurement dust concentration

Asbestos exposure limits and measurement of airborne dust concentrations... 

Capture efficiency could be measured in the same way with a tracer gas. The difficulties explained above could make this measurement le.ss reliable even if it usually is easier to measure the concentration of a tracer gas than the concentration of a specified dust or gas mixture. 

Atmospheric dust concentration The dust burden present in atmospheric air measured in mg m ... 

Different test methods produce numerically different results and comparisons should only be made of results using the same test method. Tests fall into three categories gravimetric tests, which measure ability to trap and retain dust those which measure staining power of contaminants before and after filtration and those measuring the concentration of a test aerosol either side of the filter by photoelectric methods. The tests which will be met most often are as follows. 

The standard unit normally used for measuring dust particles is the micron (pm one-thousandth of a millimeter). The smallest particle visible to the unaided eye is between 50 and 100 pm and the most dangerous sizes are between 0.2 and 5 pm. Particles larger than this are usually unable to penetrate the lung defenses and smaller ones settle out too slowly. Some dusts can be both toxic and fibrous (e.g. asbestos) and are therefore harmful even outside these parameters. It may therefore be assumed that dusts which are visible (i.e. between 50 and 100 pm), are quite safe. However, this is not the case, as dust clouds never consist solely of particles of one size. Analysis would show percentages of all sizes, and it is for this reason that special care is needed in measuring dust clouds and concentrations. 

In each of these plants, the characterization of the dust explosion potential was carried out by sampling transport ducts for explosive dust concentrations during an actual plant operation. The critical measurements taken were the quantification of explosive dust concentrations and level of electric energy generated from the electrostatic charge accumulations found in the duct. 

In order to characterize the concentration of dust flowing inside a duct, a measured amount of dust must be extracted over a known period of time. This collection velocity must be the same as the internal duct flow velocity to avoid altering the distribution of dust particle sizes. In addition, a number of sample points over the entire duct cross sectional area is necessary to define the overall dust concentration. This method of sampling, known as gravimetric sampling under isokinetic conditions, was used to determine the dust concentrations at the various manufacturing areas in the Army Ammunition Plants. 

Duct Velocity, Flow Rates, and Dust Concentration Measurements The processes monitored were not continuous therefore, the... 

Our first cotton dust measurements were made in 1967 when one of the authors of this paper measured the ambient dust concentrations downwind from three Mississippi cotton gins (4). 

Airborne dust concentrations inside Midsouth and Texas gins were measured by Wesley (12, 13) in 1972, 1973 and 1974 and are summarized in Table I. The gins did not have the same hourly... 

The alternative Instrument used was a Portable Continuous Aerosol Monitor (PCAM) manufactured by ppm, Inc., and dust concentrations measured with the PCAM were 5-15% lower than values obtained with standard vertical elutriators. Calculations and examples for TWA exposures, equivalency tests, and vertical elutriator coefficients of variation are included. 

The algebraic calculations of the distribution parameters included all cells of the histogram while those obtained from the cumulative plots were sometimes based on only a part of the cells. When the distribution was multimodal, the latter calculations included only the values from the distribution with the smaller diameter, and no attempt was made to adjust the percentage count for the number of points in the larger dicuneter distribution(s). Other factors reported are the number of particles per 0.1 ft, the dust concentration measured with the Vertical Elutriator Cotton Dust Samplers (VE), the nature of the cumulative plots, and for multimodal distributions, the percent of particles in the distribution with the smaller dieuneter. 

Humidifier Effects on Dust Concentrations Measured in a Model Card Room Without Feeding Cotton to the Opening-Carding System (23)... 

Dust Concentrations Measured in a Textile Mill with Vertical Elutriator Samplers as a Function of Variation in Water in Humidifier System. (25)... 

Considering the migration possibilities of such chemicals from their original products, complex studies were performed for classical plasticizers such as DEHP or DBP to evaluate the relevance of each pathway to human exposure assessments. Therefore, the total exposure of adults of such plasticizers was evaluated by quantifying the target substances in duplicate diet portions (collected daily over 7 consecutive days), and also by measuring indoor air and dust concentrations [129]. The results indicate that dietary exposure is the dominant... 

The progression of symptoms may continue after dust exposure ceases. Although there may be a factor of individual susceptibility to a given exposure to silica dust, the risk of onset and the rate of progression of the pulmonary lesion are clearly related to the character of the exposure (dust concentration and duration). The disease tends to occur after an exposure measured in years rather than in months. It is generally accepted that silicosis predisposes to active tuberculosis and that the combined disease tends to be more rapidly progressive than uncomplicated silicosis. 

In another study, Ott et al. (1996) measured particle concentrations inside and outside a tavern before and after a smoking ban was instated. Average respirable suspended particle mass concentrations were 57 /xg m-3 above the outdoor concentrations prior to the ban, compared to 6-13 /xg m-3 afterward. Cooking and resuspended dust also contributed to the indoor particle mass concentration, but at concentrations about 20-25% of that due to cigarette smoke. 

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