28 Indian Farming I T is essential to follow certain guidelines to maintain biosafety in the laboratory. Biological safety cabinets (BSCs) are the most commonly used primary containment devices for preventing the escape of biohazardous materials into the laboratory environment. Four classes of BSCs are recognized: Class I, Class II-Type-A, Class II-Type-B and Class III. All four classes are suitable for work with biohazardous materials in BSL1 to BSL3. The class I BSC is an open fronted, negative pressure, ventilated cabinet that provides personnel and environmental protection by means of an inward air flow away from the operator. The exhaust air is filtered through High Efficiency Particulate Air (HEPA) Filters before being discharged from the cabinet either into the laboratory or outside. The class I BSCs are no longer manufactured on a regular basis and many are being replaced by Class II BSCs. Usage should be limited to low to moderate risk biohazardous 1 Senior Scientis, 3 Research Associate; 3 Senior Research Fellow, School of Studies in Microbiology, Jiwaji University, Gwalior, Madhya Pradesh Biosafety guidelines for handling of hazardous pathogens S Nandi 1 , Pawan Kumar 2 and Prabhat Kumar 3 Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh 243 122 Biosafety has become the demand of high standard laboratory to ensure healthy working conditions. The maintenance of biosafety in the laboratory is essential for preventing laboratory-acquired infections in humans and escape of potentially hazardous pathogens to animal populations. Scientists, teachers, researchers engaged in carrying out serological, microbiological and molecular techniques should be well acquainted about the consequences of different pathogens including genetically modified organisms in man, animal and environment. protection of air recirculated, velocity of inflow air, manner of exhaust discharge, and whether contaminated air plenums are under positive pressure. The specifications of the class I, class II type A, class II-type B and class III have been given below. Class I a) Face velocity at least 75 fpm. b) Exhaust filter efficiency of 99.97% for 0.3 ìm particles. Class II –Type A a) Face velocity at least 75 fpm. b) Leak tightness less than 0.0001 cc/sec at 2 inches water gauge pressure. c) Exhaust filter efficiency of 99.97% for 0.3 ìm particles. Class II –Type B a) Face velocity at least 100 fpm. b) Exhaust filter efficiency of 99.97% for 0.3 ìm particles. Class III a) Negative pressure internally of less than 0.5 inches, w.g. b) Leak tightness less than 0.00001 cc/sec at 3 inches w.g. pressure. c) Both HEPA exhaust filters must be certified to have filtration agents. If low levels of toxic chemicals or radionuclides are used, the class II- Type B BSC is used. The class I BSC functions to protect the user and environment, but not the experiment. Therefore, it accommodates experiments using equipment such as sonicators, shielded centrifuges, blenders and mixers. The cabinet is a partial containment unit. Its barrier-function is compromised by the sudden withdrawal of the hands, the opening and closing of the room door or rapid movement past the front of the cabinet. The experimenter’s hands and arms are not protected from contact with hazardous materials, therefore, the use of protective gloves and other protective clothing and the use of appropriate techniques is of utmost importance. The class II BSC is a front opening cabinet with inward air flow to protect personnel, HEPA-filtered vertical laminar air flow to protect the work, and HEPA-filtered exhaust for environmental protection. These are most commonly referred to as laminar air flow hoods. There are two types of class II BSCs, A and B, that differ principally as to vertical dimensions of the front opening,