Automated abrasive blasting equipment for use on steel structures.
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Automation↗
Biomedical subjects
R L Mickelsen
Publications and source records attributed to R L Mickelsen.
Evaluating engineering controls during asphalt paving using a portable tracer gas method.
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Air Pollutants, Occupational↗
Factory performance evaluations of engineering controls for asphalt paving equipment.
This article describes a unique analytical tool to assist the development and implementation of engineering controls for the asphalt paving industry. Through an agreement with the U.S. Department of Transportation, the National Asphalt Pavement Association (NAPA) requested that the National Institute for Occupational Safety and Health (NIOSH) assist U.S. manufacturers of asphalt paving equipment with the development and evaluation of engineering controls. The intended function of the controls was to capture and remove asphalt emissions generated during the paving process. NIOSH engineers developed a protocol to evaluate prototype engineering controls using qualitative smoke and quantitative tracer gas methods. Video recordings documented each prototype's ability to capture theatrical smoke under "managed" indoor conditions. Sulfur hexafluoride (SF6), released as a tracer gas, enabled quantification of the capture efficiency and exhaust flow rate for each prototype. During indoor evaluations, individual prototypes' capture efficiencies averaged from 7 percent to 100 percent. Outdoor evaluations resulted in average capture efficiencies ranging from 81 percent down to 1 percent as wind gusts disrupted the ability of the controls to capture the SF6. The tracer gas testing protocol successfully revealed deficiencies in prototype designs which otherwise may have gone undetected. It also showed that the combination of a good enclosure and higher exhaust ventilation rate provided the highest capture efficiency. Some manufacturers used the stationary evaluation results to compare performances among multiple hood designs. All the manufacturers identified areas where their prototype designs were susceptible to cross-draft interferences. These stationary performance evaluations proved to be a valuable method to identify strengths and weaknesses in individual designs and subsequently optimize those designs prior to expensive analytical field studies.
Air Pollution↗
Carbon monoxide poisonings from small, gasoline-powered, internal combustion engines: just what is a "well-ventilated area"?
This study modeled the time required for a gasoline-powered, 5 horsepower (hp), 4-cycle engine to generate carbon monoxide (CO) concentrations exceeding the National Institute for Occupational Safety and Health 200-ppm ceiling and 1200-ppm immediately dangerous to life and health concentration for various room sizes and ventilation rates. The model permitted the ambiguous term "well-ventilated area" to be defined. The model was compared with field data collected at a site where two workers were poisoned while operating a 5-hp concrete saw in a bathroom having open doors and an operating ventilation system. There is agreement between both the modeled and field-generated data, indicating that hazardous CO concentrations can develop within minutes. Comparison of field and modeling data showed the measured CO generation rate at approximately one-half of the value used in the model, which may be partially because the engine used in the field was not under load during data collection. The generation rate and room size from the actual poisoning was then used in the model. The model determined that ventilation rates of nearly 5000 ft3/min (120 air changes per hour) would be required to prevent the CO concentration from exceeding the 200-ppm ceiling for short periods. Results suggest that small gasoline-powered engines should not be operated inside of buildings or in semienclosed spaces and that manufacturers of such tools should improve their warnings and develop engineering control options for better user protection.
Air Pollution, Indoor↗
Control of ethyl methacrylate exposures during the application of artificial fingernails.
In 1990 six cases of physician-diagnosed occupational asthma in cosmetologists working with artificial fingernails prompted the Colorado Department of Health to request the assistance of National Institute for Occupational Safety and Health (NIOSH) researchers in the evaluation and control of nail salon technician exposure. A commercially available recirculating downdraft table with charcoal filters was purchased and evaluated. Researchers from NIOSH made modifications to the table that included increasing the downdraft air volume; enlarging the plenum for more consistent airflow rates at the face of the table; removing the charcoal filters while incorporating a ventilation system to the outdoors; and putting an extension around the duct leading to the perforated plate at the downdraft face of the table. An evaluation was performed using the following two configurations: the modified table with the downdraft ventilation on (vented) and without the downdraft ventilation on (unvented). Each of the two configurations was sampled for 3 days in random order. Testing included the use of XAD-2 solid sorbent tubes for determining ethyl methacrylate and methyl methacrylate concentrations. Relative concentrations of organics were examined and used to analyze work practices. The geometric mean ethyl methacrylate exposure for personal breathing zone samples when using the modified table for approximately 6 hours was 0.6 ppm; when using the unventilated conventional table, the geometric mean exposure was 8.7 ppm. The difference in the values is statistically significant (p = 0.0045). Methyl methacrylate concentrations were nondetectable on all sorbent tubes.
Air Pollutants, Occupational↗
Successful reduction of silica exposures at a sanitary ware pottery.
Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted a joint survey with the New Jersey Department of Health (NJDOH) to measure crystalline silica exposures and evaluate the adequacy of the existing control measures for reducing these exposures at a sanitary ware pottery. This survey found that 95% of the personal and area samples from the Slip House, Casting, Glaze Spray, and Glaze Preparation Departments exceeded the NIOSH Recommended Exposure Level (87% exceeded the Occupational Safety and Health Administration Permissible Exposure Level) for crystalline silica. Three years later, a follow-up survey found statistically significant reductions in respirable crystalline silica exposures in two of four plant departments, and statistically significant reductions in area concentrations in all four plant departments. These reductions were accomplished through a combination of automating and enclosing the batching system in the Slip House and by replacing the mold parting compound with a nonsilica material, altering the method of dry sweeping, cleaning of castings while damp, improving exhaust ventilation at the spray booths, and improved housekeeping.
Household Articles↗
Evaluation and control of worker exposure to fungi in a beet sugar refinery.
A study of worker exposure to airborne fungi was undertaken in a sugar beet refinery to evaluate the level of exposure and to determine if controls could be implemented that would lower these exposures. A previous study at this refinery identified one worker who reacted on challenge testing to the moldy but not the fresh sugar beet pulp, had specific Immunoglobulin G to Aspergillus niger, and specific Immunoglobulin E to Aspergillus. Also, two employees were diagnosed with occupational asthma. In the study reported here, two field surveys were conducted, the first during the sugar production campaign (January) and the second during postproduction cleanup and maintenance (June). Approximately 65 personal and area air samples were collected on polycarbonate filters and the culturable fungal spores were identified and enumerated. This study showed high exposure of pellet loaders and pellet silo workers to various species of Aspergillus. Other fungal species that might pose a health hazard were detected. Exposures to fungi during the postproduction cleanup and maintenance phase were much higher than those measured during the production campaign. Engineering controls that would reduce employee exposure are discussed.
Air Microbiology↗
Evaluation of a simple weight-loss method for determining the permeation of organic liquids through rubber films.
The standard ASTM method for determining permeation of liquid penetrants through polymeric films (F739-85) was compared with a simple weight-loss method. The weight-loss permeation cell was constructed of off-the-shelf components, a conventional analytical balance was used to measure the weight loss, and a chamber with continuous ventilation was used to hold the cell at constant temperature and evacuate the permeating penetrant. The advantages and limitations of the weight-loss method were illustrated by using data obtained from the permeation of acetonitrile, n-hexane, and methanol through films of four acrylonitrile-butadiene copolymers. The steady-state flux obtained by using the weight-loss method gave results statistically equivalent to the more analytically complex ASTM standard method. The weight-loss method required the experimenter to monitor the weight of the cell and its contents over time to obtain the steady-state flux whereas the ASTM method required the experimenter to chemically analyze for the penetrant concentration in the effluent gas stream as a function of time. The ASTM method required more analytical skill and training and more costly analytical equipment than did the simple weight-loss method. The weight-loss method needs further improvement and validation but shows promise even in its present form. By using the weight-loss method, the potential exists for far more chemical protective clothing users to conduct their own low-cost permeation testing as an initial screening to determine the relative permeation performance of candidate protective clothing materials. The weight-loss method is not meant to replace the standard ASTM method but to supplement it as a screening test.
Evaluation Studies as Topic↗
A portable chemical protective clothing test method: application at a chemical plant.
The National Institute for Occupational Safety and Health (NIOSH), in cooperation with Monsanto Chemical Company, conducted an on-site evaluation of chemical protective clothing at Monsanto's Nitro, West Virginia plant. The Monsanto plant manufactures additives for the rubber industry including antioxidants, pre-vulcanization inhibitors, accelerators, etc. This survey evaluated six raw materials that have a potential for skin absorption: aniline, cyclohexylamine, diisopropylamine, tertiary butylamine, morpholine and carbon disulfide. Five generic glove materials were tested against these chemicals: nitrile, neoprene, polyvinylchloride, natural latex and natural rubber. The NIOSH chemical permeation portable test system was used to generate breakthrough time data. The results were compared to permeation data reported in the literature that were obtained by using the ASTM F739-85 test method. The test data demonstrated that aniline has too low a vapor pressure for reliable analysis on the portable direct reading detectors used. The chemical permeation test system, however, provided comparable, reliable permeation data for the other tested chemicals. Monsanto has used this data to better select chemical protection clothing for its intended use.
Chemical Industry↗
A breakthrough time comparison of nitrile and neoprene glove materials produced by different glove manufacturers.
Specimens of similar nominal thickness from commercially available nitrile and neoprene gloves were each tested for breakthrough time against three chemicals. The null hypothesis was that the breakthrough times for the glove specimens of the same generic type but produced by different manufacturers would be the same. Breakthrough time data for each material/chemical combination were analyzed using an analysis of covariance to adjust for differences in the measured specimen thickness while testing for product differences. A significant difference in chemical breakthrough times was found among generically similar products produced by different manufacturers. The largest difference between the mean breakthrough time of two generically equivalent products, 30 vs. 300 min, was obtained for perchloroethylene through nitrile products. In conclusion, breakthrough time data for use in selection of chemical protective clothing or in prediction modeling for chemical protective clothing should be manufacturer and product specific.
Acetates↗
Permeation of chemical protective clothing by three binary solvent mixtures.
An evaluation of glove materials against three different binary chemical mixtures selected from common industrial solvents was conducted. Changes in breakthrough time and permeation rate of the mixture components were evaluated as a function of the mixture composition. An increase in employee risk resulting from early mixture breakthrough time and enhanced mixture permeation rate over that of the pure chemicals was demonstrated. The permeation of a binary mixture through chemical protective clothing could not be predicted by the permeation results of the pure components. It is recommended that chemical protective clothing be tested for its permeation characteristics with the use of the chemical mixtures and conditions that reflect the work site exposure.
Clothing↗
Chemical protective clothing: a comparison of chemical permeation test cells and direct-reading instruments.
Chemical permeation of acetone through unsupported Neoprene using the ASTM cell and another commercially-available, but smaller, test cell was compared. Also, different portable direct-reading instruments were used to determine breakthrough time and steady-state permeation. The breakthrough times between the two permeation cells and among different portable direct-reading instruments were not statistically different. However, steady-state permeation rates between the two cells using the same direct-reading instrument were statistically different. Chemical permeation test methods suitable for field evaluation of chemical protective clothing are discussed.
Acetone↗
Evaluation of leakage from a metal machining center using tracer gas methods: a case study.
To evaluate the efficacy of engineering controls in reducing worker exposure to metalworking fluids, an evaluation of an enclosure for a machining center during face milling was performed. The enclosure was built around a vertical metal machining center with an attached ventilation system consisting of a 25-cm diameter duct, a fan, and an air-cleaning filter. The evaluation method included using sulfur hexafluoride (SF6) tracer gas to determine the ventilation system's flow rate and capture efficiency, a respirable aerosol monitor (RAM) to identify aerosol leak locations around the enclosure, and smoke tubes and a velometer to evaluate air movement around the outside of the enclosure. Results of the tracer gas evaluation indicated that the control system was approximately 98% efficient at capturing tracer gas released near the spindle of the machining center. This result was not significantly different from 100% efficiency (p = 0.2). The measured SF6 concentration when released directly into the duct had a relative standard deviation of 2.2%; whereas, when releasing SF6 at the spindle, the concentration had a significantly higher relative standard deviation of 7.8% (p = 0.016). This increased variability could be due to a cyclic leakage at a small gap between the upper and lower portion of the enclosure or due to cyclic stagnation. Leakage also was observed with smoke tubes, a velometer, and an aerosol photometer. The tool and fluid motion combined to induce a periodic airflow in and out of the enclosure. These results suggest that tracer gas methods could be used to evaluate enclosure efficiency. However, smoke tubes and aerosol instrumentation such as optical particle counters or aerosol photometers also need to be used to locate leakage from enclosures.
Aerosols↗