The third most effective means of controlling hazards is engineered controls. These do not eliminate hazards, but rather isolate people from hazards.[2] Capital costs of engineered controls tend to be higher than less effective controls in the hierarchy, however they may reduce future costs.[5] For example, a crew might build a work platform rather than purchase, replace, and maintain fall arrest equipment. "Enclosure and isolation" creates a physical barrier between personnel and hazards, such as using remotely controlled equipment. Fume hoods can remove airborne contaminants as a means of engineered control.[4]