A surgical mask is used inside the operating room or during other sterile procedure areas to protect the patient environment from contamination. Surgical masks have ties so that they can be adjusted for fit, and are tied over the top of a surgical or bouffant cap.
rockfall. 1  an act or instance of the falling of rock, as in a cave-in or an avalanche. 2  a mass of rocks that have fallen: to be trapped under a rockfall.
Fracking involves injection of a large volume of water, sand and a cocktail of chemicals (known as fracking fluid) deep underground to fracture the rock and allow gas to seep out. It is also used for oil extraction. (See EPA diagram at bottom.).