For specific applications, polycarbonate may be used. There are two main types of glass used for a fume hood sash: tempered and laminated safety glass. In the case of an explosion, sashes are designed to “spiderweb” instead of shattering, keeping those in the area safe from glass and chemicals. The sash works as a blast shield to provide protection and containment in the event of a fire. They offer the advantages of both vertical and horizontal sashes. Combination sashes combine horizontal sash panes, in a vertical rising frame.They provide the best access to the top interior of the hood but do not provide access to the entire width at the same time. Horizontal sashes slide from left to right, allowing a user to position themselves behind the sash for protection while enabling access through the sides.They provide the most access to the workstation because the window slides up and down. National Institute of Building Sciences ” “ Renovating Research Laboratories by Dan Watch. There are three types of fume hood sashes: vertical, horizontal, and combination vertical and horizontal. Though the VAV system conserves more energy, it costs much more than the CAV system. When the sash is closed, VAV systems are employed, which reduces the volume of the air exhausted. The vented air volume is controlled by the sash height, so a lower sash means lower air exhausted to save energy and expenses. These hoods vary the volume of air from the room that is exhausted while maintaining the face velocity at a predetermined level. Closing the sash on a CAV hood will increase the face velocity, which could potentially push contaminated air back into the room.Ī minority of fume hoods have VAV ventilation. Constant air volume ventilation provides a constant flow of air, whether the sash is open or not. There are two types of fume hood exhaust systems constant air volume (CAV) and variable air volume (VAV). The sash window provides both containment and protection from hazardous materials.īecause fume hoods are constantly working to filter the air, they can use as much energy in a day as three or four residential homes when the sash is open. The glass window slides open and closed, allowing access to the workstation. The sash refers to the front window or “door” of a fume hood. A fume hood is made up of a hood body baffles, which are partitions used to create slotted openings along the back of the hood body airfoils, which stream-line airflow into the hood the work surface an exhaust plenum, which helps to distribute airflow evenly across the hood face the face and the sash.
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