Contaminant dispersion in the vicinity of a worker in a uniform velocity field

Welling, Irma; Andersson, Ing-Marie; Rosén, Gunnar; Räisänen, Jouni; Mielo, Timo; Marttinen, Keijo; Niemelä, Raimo

doi:10.1016/s0003-4878(99)00081-2

Cited by 31 publications

(33 citation statements)

References 10 publications

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“…Although it has been suggested that body heat convection would strengthen the wake and transportation of contaminant into the breathing zone 7) , this phenomenon was not observed in the present study, possibly due to the fact that the exhaust air current around the human subject was insufficient to form an obvious wake.…”

Section: Short Communicationcontrasting

confidence: 75%

“…2, an additional experiment was performed in conjunction with a local exhaust ventilation (LEV) system. It is known that the exhaust air current of a LEV often creates a wake 7) which can cause accidental exposure. In order to examine the combined effect of body heat convection and LEV wake, the human subject was placed in front of the LEV hood and the ethanol exposures were measured in the presence of the exhaust air current.…”

Section: Short Communicationmentioning

confidence: 99%

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Gaseous Contaminant Distribution in the Breathing Zone

Ojima

2012

INDUSTRIAL HEALTH

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Conventionally, the "breathing zone" is defined as the zone within a 0.3 m (or 10 inches) radius of a worker's nose and mouth, and it has been generally assumed that a contaminant in the breathing zone is homogeneous and its concentration is equivalent to the concentration inhaled by the worker. However, several studies have mentioned that the concentration is not uniform in the breathing zone when a worker is close to the contaminant source. In order to examine the spatial variability of contaminant concentrations in a worker's breathing zone, comparative measurements of personal exposure were carried out in a laboratory. In experiment, ethanol vapor was released in front of a model worker (human subject and mockup mannequin) and the vapor concentrations were measured at two different sampling points, at the nose and at the chest, in the breathing zone. Then, the effects of the sampling location and the body temperature on the exposure were observed. The ratios of nose concentration to chest concentration for the human subject and the mannequin were 0-0.2 and 0.12, respectively. The exposure level of the mannequin was about 5.5-9.3 times higher than that of the human subject.

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Section: Short Communicationcontrasting

confidence: 75%

Section: Short Communicationmentioning

confidence: 99%

Gaseous Contaminant Distribution in the Breathing Zone

Ojima

2012

INDUSTRIAL HEALTH

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“…Karaismail 10) mentioned that a worker's movements could be one of the most important factors affecting the level of exposure in real work. For example, a human worker's arm movements can enhance mixing, which may lead to higher exposure 8,12) . However, a squatting worker does not seem to make large arm movements like a standing worker using an industrialtype benchtop enclosing hood 10) .…”

Section: Discussionmentioning

confidence: 99%

An Empirical Study on the Wake Around a Squatting Worker in a Confined Space

Ojima

2014

Journal of Occupational Health

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An Empirical Study on the Wake Around a Squatting Worker in a Confined Space: Jun OJIMA. National Institute of Occupational Safety and Health— Objectives When an air current flows from behind a worker, the contaminant level in the breathing zone may increase due to the wake around the worker. Researchers have been investigating about this wake, and much knowledge has been provided about the wake that appears around a standing worker. However, the wake around a squatting worker has not been addressed. This study aimed to describe the wake in front of a worker squatting in a confined space by using a model worker and a chamber and investigate the conditions in which this wake develops easily. Methods A mannequin was employed as a model worker and was placed in the chamber to simulate a squatting worker in a confined space. Then, air was sent from behind under various conditions with a fan, and the wake was observed. Results A wake appeared when smoke was emitted at 0–0.1 m from the point just below the breathing zone, and most of the wake region was in the range between the point just below the model worker's breathing zone and body. A wake did not appear when a fan of 0.15 m in diameter was used. The flow rate and velocity of the airflow were almost irrelevant with respect to wake development. Conclusions The following are recommended based on the results of the present study. i) The distance between a source of contaminants and the point just below the breathing zone should be more than 0.2 m. ii) An air duct with a cross‐section of less than 0.02 m2is desirable to avoid producing a wake.

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“…This study along with others [4,12,14,21,29,52] in abatement of hazardous building materials demonstrates the importance of engineering and work practice controls. A recent study [53] has also suggested that contaminant dispersion is also important when considering occupational exposure.…”

Section: Discussionmentioning

confidence: 99%

Effectiveness of Engineering Controls for Airborne Lead Exposure during Renovation/Demolition of a Commercial Building

Lange¹,

Thomulka

2000

Indoor Built Environ

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Airborne lead exposure was evaluated during renovation/demolition of a building that contained lead-based paint (LBP). During this work, different engineering and work practice controls were utilized for prevention and reduction of worker exposure to lead. These results suggest that the highest exposure occurred when no engineering or work practice controls were employed. Summary exposure levels under these conditions exceeded the Occupational Safety and Health Administration (OSHA) Permissible Exposure Level (PEL). When engineering/work practice controls, in the form of negative air machine filtration (NAM) and wet methods were used, airborne concentrations of lead were well below the OSHA PEL (50 µg·m^–3) and action level (30 µg·m^–3). Employment of NAM without wet methods reduced arithmetic mean exposure below the OSHA PEL and geometric mean below the OSHA action level. Occupational exposure concentration with NAM/wet methods was statistically lower when compared to no NAM/no wet methods and NAM/no wet methods. Exposure concentrations exhibited a nonnormal distribution. Comparison of within and between-worker variability suggests that process/environmental conditions (engineering/work practice controls) govern exposure. This study suggests employment of engineering and work practice controls for lead abatement and that process or environmental controls as compared to individual work practices/tasks are most important in controlling exposure. Study results support employment of NAM/wet method controls during renovation or demolition of building materials that contain LBP.

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Contaminant dispersion in the vicinity of a worker in a uniform velocity field

Cited by 31 publications

References 10 publications

Gaseous Contaminant Distribution in the Breathing Zone

Gaseous Contaminant Distribution in the Breathing Zone

An Empirical Study on the Wake Around a Squatting Worker in a Confined Space

Effectiveness of Engineering Controls for Airborne Lead Exposure during Renovation/Demolition of a Commercial Building

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