INTRODUCTION : You read about the fire hazards, general precautions and remedial measures in case of an outbreak of fire in the previous unit. In this unit you will learn about two other common hazards. These are the hazards because of radiation and chemical substances i.e., substances hazardous to health. The radiation hazard is generally common in a physics laboratory; however, it is equally important for a biology or chemistry technician who has to handle radioactive isotopes, used as tracers. On the other hand a chemical hazard is more likely in chemistry or a biology laboratory; yet it cannot be ignored in a physics laboratory. Therefore proper attention should be given by all the staff working in a laboratory to these hazards. In the next unit you will study about the hazards in a biology laboratory.