Mist control at a machining center, Part 1: Mist characterization.

At a machining center used to produce transmission parts, aerosol instrumentation was used to quantitatively study mist generation and to evaluate the performance of an air cleaner for controlling the mist. This machining center drilled and tapped holes at rotational speeds of 1000 to 3000 rpm. During most machining operations, the metal-working fluid (MWF) was flooded over the part. To facilitate metal chip removal during some operations, MWF was pumped through the orifices in some tools at a pressure of 800 psi. These machining operations were performed in a nearly complete enclosure that was exhausted to an air cleaner at a flow rate of 1.1 m3/sec (2400 ft3/m). Although the use of high-pressure MWF increased the mist concentration by about 200%, it did not affect the mist size distribution. The observed penetration through the air cleaner appeared to be mostly consistent with the manufacturer's specifications on the air cleaner's filters. During the testing, MWF was observed to accumulate in the bottom of the filter housing and may have been reentrained due to air motion or mechanical vibration.

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.

Case study: control of methylene chloride exposures during furniture stripping.

Methylene chloride, a potential occupational carcinogen, is one of the principal solvents used for furniture stripping. Methylene chloride exposures among workers in furniture stripping operations have been found to be high. This article describes a furniture stripping operation at a sheltered workshop before and after the ventilation system was modified. Previous to ventilation system modifications, workers who were stripping furniture had exposures to methylene chloride ranging from 600 to 1150 ppm. These high exposures and an evaluation of the ventilation system prompted the design and installation of a modified ventilation system. Primary modifications included installing a local ventilation hood, decreasing the velocity of makeup air entering the stripping area, removing a contaminated charcoal adsorption bed and improving work practices. The modified system was arranged into three configurations that included a slot hood, a downdraft hood, and a combination slot and downdraft hood. The three configurations were evaluated over a three-day period, and it was found that they controlled the worker's personal exposures to methylene chloride while stripping to 28 ppm for the combination configuration, 30 ppm for the downdraft configuration, and 34 ppm for the slot configuration. Although the exposures are above the proposed Occupational Safety and Health Administration permissible exposure level of 25 ppm, these results show a substantial improvement over the existing ventilation system. The ventilation system described is applicable to other furniture stripping facilities if rinse area local ventilation is improved.

A hazard and operability study of anhydrous ammonia application in agriculture.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) applied Hazard and Operability (HAZOP) analysis to examine hazards during the use of anhydrous ammonia by farmers. This analysis evaluated the storage, transfer, and application of anhydrous ammonia, identifying credible hazard scenarios, practical solutions, and research needs. Ninety-five findings were developed that are of use to farmers, distributors of ammonia and application equipment, and manufacturers of application equipment. The findings generally involve training, equipment design changes, preventive maintenance, and material compatibilities. The HAZOP team found that additional safety features need to be developed or implemented. The study also pointed out where correct operator procedure and preventive maintenance can prevent inadvertent releases. Other inadvertent releases are caused by incompatible materials, or by using equipment in ways other than intended. Several examples of the findings are given to emphasize the HAZOP technique and the high-risk scenarios. Strategies for dissemination to the agricultural community are presented.

Cathodoluminescence properties of lunar rocks.

Calcic plagioclase is the dominant luminescent mineral in crystalline rocks and breccias. Minor amounts of cristobalite and tridymite are also luminescent, as are trace grains of potassium feldspar. Two types of intergrowths of potassium feldspar with a silica phase, possibly quartz, were found in the breccias. Luminescence spectra of plagioclase show significant similarities to, and differences from, spectra of terrestrial plagioclase. Shock damage in the breccias is reflected in systematic changes in the plagioclase spectra, thus giving evidence of disordering on the angstrom scale. Associated extinction patterns seen between crossed Nicol prisms give evidence of disordering on the micrometer scale.