ABSTRACT
A laboratory fume hood is a ventilated enclosure where harmful chemicals can be handled safely. The purpose of a laboratory fume hood is to capture and contain toxic contaminants from escaping into the laboratory. Air flow in the hood is achieved by an exhaust blower which pulls air from the laboratory into its duct work system. General purpose laboratory fume hoods are divided into three categories: conventional, by-pass air, and add-air. Ventilation is a key method for reducing employee exposures to airborne contaminants resulting from laboratory operations. Ventilation can be used either to dilute contaminants to safe levels or to capture and remove contaminants at their sources before pollution of the working environment occurs. Ventilation is required in Occupational Safety and Health Administration standards for two reasons: to control employee exposures to potentially harmful materials and to prevent fire or explosion hazards. Within both categories there are two types of requirements: performance standards and specification standards.
