Biomedical subjects

Steven E Guffey

Publications and source records attributed to Steven E Guffey.

4 recordsLinked to original sources

PubMed2005

A numerical study of worker exposure to a gaseous contaminant: variations on body shape and scalar transport model.

Three-dimensional computational fluid dynamics simulations are used to investigate the distribution and level of contaminant concentrations in the true breathing zone (at the nose and mouth) when toxic airborne contaminants are released within an arm's length in front of the worker who has his back to the airflow. The effects of different body shapes on fluid flow and concentration patterns around the body in a wind tunnel were evaluated and clarified that a sharp body or a block may not be a good surrogate for the human form in consideration of occupational and environmental health studies. The comparison of the concentration field calculated with the Eulerian and Lagrangian methods revealed that the Eulerian method has a more diffusive nature than the Lagrangian method. The concentrations at different locations were also compared to determine the optimum sampling location. It was found that the concentration at the breathing zone may be significantly different from the one at the chest area. The influence of the heat flux from the body was studied at two different Reynolds numbers. Predictions indicate that the heat flux may have a significant impact on exposure especially when the convection induced by buoyancy dominates the flow.

Air Pollutants↗

PubMed2004

Applying open-path FTIR with computed tomography to evaluate personal exposures. Part 1: simulation studies.

This paper presents the theoretical background and the numerical evaluation results obtained using computed tomography coupled with open-path Fourier transform infrared (CT-FTIR) measurements to estimate personal exposures. In this simulation study, we first tested the one-dimensional scenario with a five-beam segment geometry. A series of Gaussian plumes and the corresponding path-integrated concentrations (PICs) were simulated. The personal exposures were estimated as the average of the point estimates calculated from the workers' locations and the concentration profiles reconstructed from the Smooth Basis Function Minimization algorithm. It was found that the running-average PIC updating strategy has similar performance as the spline PIC updating strategy. However, the latter strategy gives delayed estimates of the workers' exposures since it requires additional measurements before and after the time period of interest. In the two-dimensional scenario, we simulated a series of single-mode bivariate Gaussian plumes with a nine-beam radial geometry. The average of the estimated exposures from the CT-FTIR approach was close to the average of the true exposures. The concordance correlation factors between the true and estimated exposures were reasonably good (between 0.50 and 0.58). This study demonstrated that the CT-FTIR approach is feasible for industrial hygiene monitoring.

Algorithms↗

PubMed2004

Field evaluation of methods for determining the obstructed section of branches of industrial ventilation systems.

This study proposes and evaluates the effectiveness of three methods in determining the location of obstructions and alterations in the branches of industrial ventilation systems. Three branch-screening methods (reference ratio, static pressure ratio, and power loss coefficient methods) were adapted to determine if obstructions lay in four distinct areas of a branch. The areas were the hood, middle, and end sections, with the middle and end sections combined to form the fourth area. These methods were evaluated for their ability to detect obstructions in each specific section and also for their ability to detect obstructions in sections after the branch was surveyed for obstructions using a screening method. The results of this study indicate that each method is very useful in determining the presence and location of an obstruction in every section of the branch except the hood section. Each method performed poorly when determining obstructions in the hood section. However, because of the ability of the methods to detect obstructions in the other three sections, the process of elimination can be used with confidence to determine obstructions in the hood.

Environmental Monitoring↗

PubMedDate not supplied

The effect of local exhaust ventilation controls on dust exposures during concrete cutting and grinding activities.

This study assessed the effectiveness of commercially available local exhaust ventilation (LEV) systems for controlling respirable dust and crystalline silica exposures during concrete cutting and grinding activities. Work activities were performed by union-sponsored apprentices and included tuck-point grinding, surface grinding, paver block and brick cutting (masonry saw), and concrete block cutting (hand-held saw). In a randomized block design, implemented under controlled field conditions, three ventilation rates (0, 30, and 75 cfm) were tested for each tool. Each ventilation treatment was replicated three times in random order for a total of nine 15-min work sessions per study subject. With the exception of the hand-held saw, the use of LEV resulted in a significant (p < 0.05) reduction in respirable dust exposure. Mean exposure levels for the 75 cfm treatments were less than that of the 30 cfm treatments; however, differences between these two treatments were only significant for paver block cutting (p < 0.01). Although exposure reduction was significant (70-90% at the low ventilation rate and 80-95% reduction at the high ventilation rate), personal respirable dust [corrected] exposures remained very high: 1.4-2.8 x PEL (permissible exposure limit) at the low ventilation rate and 0.9-1.7 x PEL at the high ventilation rate. Exposure levels found under actual field conditions would likely be lower due to the intermittent nature of most job tasks. Despite incomplete control LEV has merit, as it would reduce the risk of workers developing disease, allow workers to use a lower level of respiratory protection, protect workers during short duration work episodes reduce exposure to nearby workers, and reduce clean-up associated dust exposures.

Air Pollutants, Occupational↗