Experimental Measurements of Near-Source Exposure Modeling Parameters.

Area of Science:

• Environmental Engineering
• Occupational Health and Safety
• Fluid Dynamics

Background:

• Accurate modeling of air concentrations near pollutant sources is vital for assessing worker exposure.
• Two-zone and turbulent diffusion models are commonly used, each requiring specific pollutant transport parameters: interzonal airflow (β) and turbulent diffusion coefficient (DT), respectively.
• Experimental determination of these parameters, especially under dynamic conditions simulating worker actions, is necessary for model validation.

Purpose of the Study:

• To experimentally determine the interzonal airflow (β) and turbulent diffusion coefficient (DT) near a pollutant source.
• To investigate the influence of simulated worker motion on these transport parameters.
• To validate the applicability of two-zone and turbulent diffusion models for worker exposure assessment.

Main Methods:

• Conducted 82 experiments using tracer vapor release near a pollutant source within a 0.4 m hemispherical near zone.
• Employed a robot arm to simulate worker actions and introduce motion in the vicinity of the source.
• Calculated β and DT using measured concentrations, room geometry, and ventilation parameters.

Main Results:

• Both β and DT were found to be log-normally distributed.
• The mean β was 2.03 m³/min (GM: 1.65 m³/min) and the mean DT was 0.586 m²/min (GM: 0.545 m²/min).
• Simulated worker motion and room location significantly influenced the values of β and DT.

Conclusions:

• The experimental determination of β using random airspeed and free surface area was validated.
• A recently developed algorithm proved useful for determining DT.
• The findings support the enhanced application of two-zone and turbulent diffusion models in worker exposure modeling, particularly when considering dynamic near-source conditions.