The discipline of industrial hygiene is concerned with identifying and controlling potential chemical, physical, and biological workplace hazards by evaluating processes and facility designs using the following steps: Anticipation, Recognition, Evaluation, Control. Using pre-established and approved methods determined by the nature of the hazard, industrial hygienists take qualitative and quantitative measurements of potential hazards in the workplace. The results are compared to recommended exposure guidelines or consensus standards. If the results reveal a possible health hazard, industrial hygienists will recommend methods for controlling the hazard. These methods may include engineering controls and appropriate safety practices for personnel, such as the substitution of safer materials, or the use of ventilation and personal protective equipment.