Abstract: An improved breathing protective apparatus having an inhalation regulator and a primary source of breathing air supplied to the user through a pressure line, and an exhalation regulator with a return line connected to a vacuum source to remove exhaust gases from the work area is disclosed. The apparatus also has a positive pressure and free flowing regulator which provides an extra measure of safety in a toxic environment and provides low breathing resistance under high work load conditions. The arrangement is such that if the exhalation regulator is bypassed for exhaust without vacuum conditions, positive pressure and the free flowing regulator are automatically eliminated to save emergency air for escape of the user from a contaminated environment.

Abstract: A subsea caisson or silo for housing wellhead equipment and methods of installing it is disclosed. A caisson which is sized to receive equipment that is to remain subsea has a closed top and open bottom. The caisson is lowered to the seabed and hydrostatic pressure in combination with a suction jet is used to remove the internal soil. If required the caisson may include a conical suction head located near the bottom of the caisson wall and rotatable cutting heads are fixed to its lower surface so as to cut into sea bottom material of hard consistency.