Standard design methods for local exhaust hood design require the selection of the necessary capture velocity and then application of empirical equations relating capture velocity with hood flow rate. The selection of capture velocity depends on hood geometry, source generation rate, and disturbances in the vicinity of the local exhaust hood. Current design techniques for vapor degreasers require a hood flow rate of 0.25m3s-1 per m2 of tank area.(1) The design method does not account quantitatively for crossdrafts, but instead recommends eliminating crossdrafts.

In the printing office the use of dyes and solvents often results in occupational health problems. Today, target levels for industrial air quality and acceptable worker exposure are much lower than before. This makes heavy demands on the exhaust efficiency of polluting processes as well as it focuses on worker exposure. This paper describes a process of optimisation of exhaust efficiency and of minimisation of worker exposure at a semiautomatic printing machine at a printing office.

Ventilation systems can be divided in many ways, by size, flow rate, velocity, material, placing, aim, etc. One common way is to divide between General Ventilation (GV) and Local Ventilation (LV). However, these terms do not have general accepted meanings. In the Design Guide Book for Industrial Ventilation (DGB), chapter 10 Local Ventilation, we (members of COST G3 Working Group 4) have tried to define and describe Local Ventilation systems. We have also made a division of L V into different specific systems.

Exhaust hoods are used in many industries to remove contaminant from a region close to the source( s) of the generation by the withdrawal of air and contaminant. In comparison with traditional exhaust hoods, the Aaberg exhaust system, with its additional jet, can significantly improve the capture efficiency of the hood. Since the 1980's experimental investigations and mathematical analyses on the Aaberg exhaust systems have been performed by Hogsted (1), Hyldgard (2), Pedersen and Nielsen (3) Fletcher and Saunders (4) and Hollis (5).

In 1998, a program was initiated to develop an innovative backshelf hood system that could achieve a much lower capture and containment (C&C) exhaust rate than traditional backshelf hoods. As part of this effort, an evaluation of the state-of-the-art tools in use in commercial kitchen ventilation in the United States was undertaken. This paper presents the new hood concept KVL, a description of the latest techniques available for determining C&C performance, and comparisons of the KVL new hood concept to other hoods.