Hazards must be controlled first by the application of engineering controls that are supplemented by administrative controls. Personal protective equipment is only considered when other controls are not technically, operationally or financially feasible. Typically, combinations of all methods are necessary in controlling chemical hazards. Engineering controls remove the hazard, either by initial design specifications or by applying methods of substitution, minimization, isolation, or ventilation. Engineering controls are the most effective hazard control methods, especially when introduced at the conceptual stage of planning when control measures can be integrated more readily into the design.
Minimization is the expression used when a hazard is lessened by scaling down the hazardous process.
Substitution is usually the least expensive and the most positive method of controlling hazards and should always be the first engineering hazard control measure considered. Minimization should always be the next engineering control measure attempted after examining substitution followed by the consideration of isolation. Isolation is particularly useful when the material, equipment or process requires minimal contact or manipulations. When these previously mentioned control methods are not feasible, ventilation is the next desirable engineering option. The two types of ventilation are typically termed local exhaust and general ventilation .