Working with volatile chemicals creates numerous hazards for scientists in laboratory. Therefore, it isrestricted to do such works in a fume hood, which is designed to draw fresh air from the room into thehood and then out into the ventilation system, in order to prevent the accidents happened.According to the laboratory fire incidents investigation, the authors observed that a fire occurred infume hood will be a serious problem which has the potential to get much worse in the future as moreand complex laboratories are used and as the hood usage density increase.
The paper deals with research on capture efficiency of reinforced exhaust system equipped withhorizontal slot exhaust hood, capture efficiency of which is increased by radial flow of supply air through a slot in hood flange. Investigation was carried out with the use of tracer gas method applied in order to measure the capture efficiency of the system, interferometric method in order to visualize tracer gas propagation from different sources, and smoke method in order to make flow patterns at exhaust system visible.
The capture efficiency of the total system must be guaranteed so that the spread of impurities throughout the kitchen is prevented. A capture efficiency model is derived and it is used to estimate the efficiency of a ventilated ceiling. This paper demonstrates that a simple equation that includes the average contaminant level in the occupied zone and the exhaust concentration could be a suitable platform for capture efficiency analysis in both measurements and simulations.
This paper presents the study of a local exhaust ventilation system with plain (unflanged) and flanged hoods. Centerline velocity and velocity contours in front of exhaust hood openingswere measured and compared to other previously reported results. Centerline velocity correlations are derived for a full range of hood axes. The effect of turbulence intensity and surrounding equipment on the velocity contours is also analyzed. Capture velocity for three different types of contaminant particles (saw dust, wheat flour, and sand) was determined.
The conventional constant air volume exhaust fan system is actually a variable air volume system. The fan airflow increases as the fume hood airflow decreases. Under partial fume hood exhaust airflow, the fan power is higher than the design fan power. Two energy efficiency measures are developed in this study to reduce the fan power of the conventional constant air volume exhaust system. In the first measure, a modulation damper is added in the main exhaust air duct and
The classification of fume hoods in laboratories was conducted as a occupational protection part of risk assessment and management procedure. The fume hoods (n = 296) in laboratories were classified according to the observed face velocities. Classification scheme included descriptions of recommended use. Only 30 % of fume hoods were recommended for normal laboratory duties and 7 % were recommended not at all to be used.
Two-dimensional numerical simulations have been undertaken for the steady turbulent fluid flow in a room containing a fume cupboard which is attached to a wall and a ventilation duct which is situated in the ceiling of the room, see figure 1. The wall opposite to the fume cupboard is assumed to be porous and a fully developed fluid velocity profile is applied far upstream. The calculated flow is considered to be that which is actually found in the central plane of a practical fume cupboard.
Many hazardous chemicals are used in research laboratories. Fume hood is the most efficient and common single equipment used in prevention of chemical exposure of laboratory workers. Totally 303 fume hoods were inspected at the University of Kuopio laboratories and 295 of them were tested for their performance. The most important properties affecting occupational safety due to the fume hoods were tested.
54 fume hoods in three laboratory buildings in Norway were tested for containment using two tracer methods based on European and American standards, in addition to face velocity measurements. In the first method, an abridged version of Nordtest VVS 095, tracer gas was measured at one point in the sash opening, in front of a mannequin placed at the fume hood with a sash height of 30 cm. In the second method, based on ASHRAE 110-1995, tracer was measured in the breathing zone of the mannequin for a 67 cm sash height.