PubMed Health⌕ Search

Biomedical subjects

P C Reist

Publications and source records attributed to P C Reist.

At least 19 recordsLinked to original sources
PubMed1995

Efficacy of portable filtration units in reducing aerosolized particles in the size range of Mycobacterium tuberculosis.

OBJECTIVE: To evaluate engineering control measures to prevent nosocomial transmission of diseases such as tuberculosis, we studied four portable high-efficiency air filtration units, including three high-efficiency particulate air (HEPA) filtration units, for their ability to remove aerosolized particles. DESIGN: Studies were conducted in either a nonventilated aerosol chamber or in a hospital isolation room that met CDC guidelines for TB control (negative pressure, > or = 6 air changes per hour, air exhausted directly to the outside). The rooms were challenged with aerosolized mineral oil in the size range of 0.3 to 5.0 microns at levels 10 to 20 times the normal airborne particle load in the room at baseline. Airborne particles were counted with a laser counter capable of simultaneously measuring sizes > or = 0.3, > or = 0.5, > or = 1.0, and > or = 5.0 microns. Experimental runs were conducted with the filtration units in the center or corner of the chamber or room, and the particle counter in the center of the room or at the exhaust vent. RESULTS: Portable filtration units were effective in accelerating the removal of aerosolized submicron particles. In the nonventilated room, time required by the various portable filtration units for removal of 90% of aerosolized particles (> or = 0.3 microns) ranged from a low of 5 to 6 minutes to a high of 18 to 31 minutes, compared to the control (no filtration unit), > 171 minutes. In the hospital room, individual filtration units removed 90% of aerosolized particles (> or = 0.3 microns) in times ranging from 5 to 8 minutes to 9 to 12 minutes, compared to the control (no filtration unit), 12 to 16 minutes. The location of the portable filtration unit (center versus corner) did not affect the clearance rate of airborne particles. CONCLUSION: Our data indicate that portable filtration units can rapidly reduce levels of airborne particles similar in size to infectious droplet nuclei and, therefore, may aid in reducing the risk of tuberculosis exposure.

Aerosols↗
PubMed1987

Comparison of two biological aerosol sampling methods.

Two biological aerosol samplers, the Andersen two-stage microbial impactor and the May three-stage glass impinger, were examined to determine the benefits and effectiveness of the May sampler compared with the Andersen sampler, one of the most widely accepted samplers. Side-by-side samples were collected during simulated wastewater spray irrigation dispersion studies. Escherichia coli colony counts and air concentrations were statistically treated to determine the dependability of the May results with respect to the Andersen results. After data pairs containing potentially overloaded Andersen counts were eliminated, a linear regression of the remaining data was performed. It indicates that although the May sampler reports 82% of the Andersen sampler value, the correlation between the two samplers is good with an r2 value of 0.84. This comparison indicates that although there are differences between the two samplers, they do give comparable results and that when both are used in a sampling program, they tend to complement each other.

Air Microbiology↗
PubMed1986

An evaluation of the effectiveness of a recirculating laboratory hood.

Ductless, benchtop hoods have become a popular tool for use in the control of toxic substances in the laboratory. Low price and ease of installation are major factors contributing to their increased utilization. Little objective performance data exist for these devices. One such hood was evaluated for efficacy as an engineering control in typical laboratory applications. Face velocity, flow profile, ability to retain vapors, sorptive capacity of the filter media and overall worker protection were evaluated. The manufacturer's report of an average face velocity of 30.6 cm/s (60 fpm) proved to be accurate; however, this value was found to be substandard when compared with the hood and room design criteria which must be met for this rate to provide adequate control. The hood was designed in a manner which prevented smooth flow through the hood and increased observed turbulence and rolling. The sorptive capacity of the carbon filter proved to be comparable to that reported for organic vapor respirator cartridges. Design deficiencies are discussed to improve protection offered to the worker in an as-used situation. Further work is needed to provide a quantitative measure of the protection offered by these hoods.

Air Pollution↗
PubMed1984

The critical orifice revisited: a novel low pressure drop critical orifice.

The ability to maintain a constant air flow rate under varying load conditions is of basic importance in air sampling. Critical orifice flow devices are often used to accomplish this. A major disadvantage of most critical orifice designs is that a pressure drop in excess of 350 mm Hg (14 in. Hg) is required to ensure stable flow. It is possible, however, to design a flow restricting device which will function as a critical orifice at pressure drops significantly less than those required for conventional designs. Presented here is an inexpensive and convenient method for controlling flow in the range of 20-90 L/min. Pressure drop versus flow rate data demonstrate that a vacuum of 150 mm Hg (6 in. Hg) or less is required to reach critical flow conditions using this design. Thus the convenience of unattended constant flow rate control with a substantial reduction in vacuum pump capacity and cost is achieved.

Air↗
PubMed1979

Adjusting occupational exposure limits for moonlighting, overtime, and environmental exposures.

A mathematical model is used to predict relative body burdens of inhaled contaminants in workers who work two jobs or overtime, or who experience off-the-job exposure to air contaminants. Expected "peak" or maximum body burdens from multiple exposures are compared to those expected from the "normal" occupational exposure on which TLVs and Permissible Exposure Limits (PELs) arebased (five 8-hour days per week with zero off-the-job exposure). The model is designed to predict what adjustments to the TLVs and PELs are necessary to avoid accumulation of excess peak body burdens of contaminants from the additional exposures incurred. The general application of models to determine occupational exposure limits is reviewed, and several models are compared.

Air Pollutants↗
PubMed1977

Application of occupational exposure limits to unusual work schedules.

A one-compartment exponential models is described which predicts "equal protection", based on biological uptake rates, for unusual air contaminant exposure situations as compared to a "normal" exposure of five 8-hour days per week. This is done by equating peak body burdens resulting from a normal and an unusual exposure, in terms of an adjustment factor applied to the normal exposure limit for an air contaminant. This factor predicts the highest allowable concentration in an unusual exposure situation which will not result in a higher-than normal body accumulation of the inhaled substance. Graphs and formulae are provided for determining adjustment factors for anticipated unusual exposure schedules. The model's predictions and published data are compared.

Air Pollutants↗
PubMed1977

Exposure to anesthetic waste gas in oral surgery.

Exposure to nitrous oxide and halothane during oral surgery was monitored using a Miran infrared analyzer. A "typical" time-weighted analysis exposure was established for the surgeon, assistant, and anesthetist. Values for halothane ranged from 7.5 to 59 ppm, and for nitrous oxide, from 280 to 90,000 ppm.

Adolescent↗
PubMed1977

Odor detection and respirator cartridge replacement.

If the odor threshold of a compound is greater than its TLV, overexposure of a respirator user is possible since breakthrough may not be detected. Odor threshold data are assembled for a number of different materials and compared to their TLV's. Use practices are recommended for chemical cartidge respirators for various grouping of compounds, based on their odor threshold to TLV ratio.

Alcohols↗