MEP 1 st fix : Those which start along with block work and continue till completion of plaster eg.Duct hanger&support ,pipe hanger&support,fixing G.I conduits,back box,marking on block walls ,cutting & chasing install of concealed pipes in wall and so on
MEP 2 nd fix : Major part of building utility system starts after completion of plaster eg.ductwork installation & insulation,chilled water pipe installation & insulation,FCU/AHU installation,water heater installation
MEP final fix : Generally covers all exposed items eg. electrical light fixtures,grilles& diffusers, sprinklers and so on