Biomedical subjects

C I Fairchild

Publications and source records attributed to C I Fairchild.

5 recordsLinked to original sources

PubMed1997

Evaluation of continuous air monitor placement in a plutonium facility.

Department of Energy appraisers found continuous air monitors at Department of Energy plutonium facilities alarmed less than 30% of the time when integrated room plutonium air concentrations exceeded 500 DAC-hours. Without other interventions, this alarm percentage suggests the possibility that workers could be exposed to high airborne concentrations without continuous air monitor alarms. Past research has shown that placement of continuous air monitors is a critical component in rapid and reliable detection of airborne releases. At Los Alamos National Laboratory and many other Department of Energy plutonium facilities, continuous air monitors have been primarily placed at ventilation exhaust points. The purpose of this study was to evaluate and compare the effectiveness of exhaust register placement of workplace continuous air monitors with other sampling locations. Polydisperse oil aerosols were released from multiple locations in two plutonium laboratories at Los Alamos National Laboratory. An array of laser particle counters positioned in the rooms measured time-resolved aerosol dispersion. Results showed alternative placement of air samplers generally resulted in aerosol detection that was faster, often more sensitive, and equally reliable compared with samplers at exhaust registers.

Aerosols↗

PubMed1996

Single point aerosol sampling: evaluation of mixing and probe performance in a nuclear stack.

Alternative reference methodologies have been developed for sampling of radionuclides from stacks and ducts, which differ from the methods previously required by the United States Environmental Protection Agency. These alternative reference methodologies have recently been approved by the U.S. EPA for use in lieu of the current standard techniques. The standard EPA methods are prescriptive in selection of sampling locations and in design of sampling probes whereas the alternative reference methodologies are performance driven. Tests were conducted in a stack at Los Alamos National Laboratory to demonstrate the efficacy of some aspects of the alternative reference methodologies. Coefficients of variation of velocity, tracer gas, and aerosol particle profiles were determined at three sampling locations. Results showed that numerical criteria placed upon the coefficients of variation by the alternative reference methodologies were met at sampling stations located 9 and 14 stack diameters from the flow entrance, but not at a location that was 1.5 diameters downstream from the inlet. Experiments were conducted to characterize the transmission of 10 microns aerodynamic diameter liquid aerosol particles through three types of sampling probes. The transmission ratio (ratio of aerosol concentration at the probe exit plane to the concentration in the free stream) was 107% for a 113 L min-1 (4-cfm) anisokinetic shrouded probe, but only 20% for an isokinetic probe that follows the existing EPA standard requirements. A specially designed isokinetic probe showed a transmission ratio of 63%. The shrouded probe performance would conform to the alternative reference methodologies criteria; however, the isokinetic probes would not.

Aerosols↗

PubMed1987

Particle concentration in exhaled breath.

Measurements were made of the number concentrations of particles in exhaled breath under various conditions of exercise. A laser light scattering particle spectrometer was used to count particles exhaled by test subjects wearing respirators in a challenge environment of clean, dry air. Precautions were taken to ensure that particles were not generated by the the respirators and that no extraneous water or other particles were produced in the humid exhaled air. The number of particles detected in exhaled air varied over a range from less than 0.1 to about 4 particles per cm3 depending upon the test subject and his activity. Subjects at rest exhaled the lowest concentration of particles, whereas exercises producing a faster respiration rate caused increased exhalation of particles. Exhaled particle concentrations can limit the usefulness of nondiscriminating, ambient challenge aerosols for the fit testing of highly protective respirators.

Aerosols↗

PubMed1977

The filtration efficiency of organic vapor sampling tubes against particulates.

The particulate filtration efficiency of industrial organic vapor sampler tubes is of interest for air sampling in work environments containing toxic materials as both vapor and particulate, or where inert particles contain adsorbed toxic material. Particulate collection efficiencies, measured with dioctylphthalate and polystyrene latex aerosols ranged from 70-90%. However, only 20% of this total is deposited on the active sorbent (charcoal granules). Considerable variability in collection efficiency between tubes was observed. Recommendations are made for obtaining improved contaminant estimates using these tubes.

Air Pollutants↗

PubMed1975

Calibration standards for counting asbestos.

A laboratory proficiency testing program has been initiated by NIOSH to permit standardization of asbestos counting procedures by various state agencies. This has required preparation of multiple membrane filter samples containing "identical and predictable" concentrations of asbestos fibers, with consistent particulate backgrounds. A technique to filter liquid (toluene) suspensions was developed to provide chrysotile asbestos standards ranging from 200 to 1,500 fibers/mm-2 of filter area, with an aluminum oxide particulate background. Details of the necessary techniques are described. To evaluate variations inherent in preparing these "identical" samples and to estimate variations between different counters, extensive replicate fiber counting was performed. Count data from several counters at a single facility show that this liquid suspension filtration technique provides reproducible asbestos standards as measured by optical microscopy with a coefficient of variation of plus or minus 20% with the maximum individual variations of plus or minus 50%.

Air Pollution↗