English

The exterior hood has been used extensively in the local exhaust devices to capture a variety of contaminants generated in a working-site. The performance of a hood can be measured by either how well it captures the contaminants or how far away it can perform an effective capture. It has been known theoretically that in the presence of an uniform cross draft a capture envelope will form in front of an exhausted opening(2, 3). All streamlines inside an envelope will lead into the opening; otherwise, those outside the envelope will lead to infinity downstream.

Occupational hygiene conditions were examined in a welding shop after repairing the air-handling unit. Good indoor air quality was achieved with the new replacement ventilation system. The airborne dust concentrations varied from the detection limit of 0.1 mg/m3 to 0.8 mg/m3 at the stationary sites. Even the breathing zone concentrations of the welders remained below or equal to 2.1 mg/m3. The concentrations of carbon monoxide did not exceed the level of 1 cm3/m3.

It is of prime importance at the design stage that the designer of an industrial ventilation system makes a reasonable assessment as to the owning and operating costs of an Industrial Ventilation System. Armed with these findings the designer must consider what improvements can be made by considering a different approach or by using other types of plant. The designer must inform the owner of the plant of any alternatives.

The owning and operating costs of a system are made up of the following items:

The paper deals with a three dimensional modelling of an experimental device realized in the Department of "Fisica Tecnica" of the University of Rome "La Sapienza" in cooperation with the Italian National Council of Researchers (CNR) in order to investigate the performances of shutter type air curtains as a dynamic barrier against the diffusion of fumes or airborne toxic substances.

This paper presents the field experiments on the ventilation efficiency in an underground car park where high velocity fan-diffuser units were installed as shown in Photo 1. The concentration of SF6 were measured as tracer gas under the step up condition and the step down condition, and the ventilation efficiency such as the age of air were calculated from the rising curve and the falling curve of the SF6 concentration in the underground car park. The ventilation efficiencies of two cases were compared, i.e.

This paper presents the results of the numerical simulation on the ventilation efficiency and the residual age of air by using CFD in the underground car park in which the field measurement was conducted as shown in a previous paper. The agreement between the CFD result and the measurement one was observed at most of the measuring points. The detailed distribution of local air change effectiveness was examined with the results from CPD in this paper.

This paper attempts to provide a general basis for implementing the principles of pressure differentials to aid in providing more user friendly air quality in buildings. This is a new technology application to be added to the commonly used air changes and filtering for cleaner air. The success story of smoke control can now be used as a major strategy against pollution and disease control in buildings. Stale bacteria-infiltrated air can also be contained to its spaces of origin and exhausted from its sources in the building.