When people work with electrical appliances, health and safety regulations say that the appliance must be; the interval between tests depending on both the type of appliance and the environment it is used in.
The appliance must be. This is what Health and safety regulations say. The interval between tests depending on both the type of appliance. This is what Health and safety regulations say. The interval between tests depending on both the type of the environment. This is what Health and safety regulations say. It is used in the environment. People work with electrical appliances.