The invention relates to an apparatus and method for use in well drilling, for separating rock cuttings, gas, water, drilling mud, gases, or foam which may be part of the drilling fluid returning from a bore hole. The apparatus has a plurality of compartments through which the drilling fluid flows. The first compartment makes use of a degasser to extract gases from the fluid, as well as break down foam. Subsequent chambers involve the use of shale shakers, centrifuges, and flocculants to aid in the separation of liquids from solids. The invention also employs a deduster unit which eliminates the spread of dust common in air drilling operations. Through the use of these various devices, the invention eliminates the need for venting the drilling fluid to the environment surrounding the well site.