When a person works facing a local exhaust ventilation (LEV) hood, it may be possible to obtain higher concentrations of aerosols in the breathing zone (BZ) than without the hood because recirculating eddies form downstream of the body. These eddies shed periodically in an alternating pattern called vortex shedding, which is thought to be a primary determinant of contaminant transport in and out of the breathing zone (1, 2, 3). Previous computational fluid dynamics (CFD) studies have explored the effect of timedependent airflow on occupational exposure to gaseous contaminants (2, 3).

Preliminary numerical simulations of human exposure to paint-spray aerosols demonstrate the ability of computational fluid dynamic (CFD) software to discriminate between two different orientations of spraying a flat plate in a cross-flow ventilated spray booth. To conduct exposure-scenario simulations using CPD, a conceptual model of reality must be created that is compatible with the computer code. If this conceptual model is not a sufficient representation of reality with regard to the desired outcome, then no matter how accurate the simulation, the results will be of limited value.

Productivity is one of the most important factors affecting the overall performance of any organization. Productivity is defined as the ratio output divided by the input used to produce the output. The output refers to products and services produced by an organization (2). Increased attention has been paid to the relationship between the work environment and productivity in the 1990s. Laboratory and field studies show that the air quality and thermal conditions at work may have a notable impact on the performance of the occupants, and consequently on labor productivity (1,3,4).

The results of indoor air quality surveys have showed that it was quite easy to fulfil the requirements of indoor climate standards and recommendations, even in office buildings where the workers experienced sick building symptoms, and complained that the reason for their symptoms was poor indoor air quality (1, 2). Many researchers consider that psychosocial factors may serve as moderators or mediators in the sick building syndrome process, either increasing or decreasing the vulnerability of the individual to environmental exposures (3, 4).

The control of emissions from open surface tanks is usually perfomed using simple exhaust systems or combined with push (1). In the first case the exhaust entries generate omnidirectional speed fields within the tank, which rapidly reduce efficiency as the distance increased and are recommended for tanks of less them 1 metre in length. In the push-pull systems, a curtain of air sweeps over the surface of the tank and drags emission towards the exhaust causing a jet wall which (2), when well formed, permits high capture efficiency (3).