INTRODUCTION : Gas, Electricity and water are integral parts of any science laboratory. You would have realised from personal experience (if any) and in the course of your study of Unit 11 that these services can also be potential hazards in the laboratory. For example, water can get sprinkled on an electrical socket by a leaking tap leading to a short circuit followed by, may be a fire. In case of an eventuality, probably the first and foremost step would be cutting down the supply of gas, electricity, or water to the lab. This necessarily means that one must know the respective control points. In fact, this exercise is intended to familiarise you regarding the source and the control points of all these essential services.