below who wishes to exit the manhole may easily lift the device upwardly and set it aside from below other suitable materials for construction of the integral molding is glass fiber reinforced epoxy resin polypropylene polymer delrin u00ae nylon and like structural materials including aluminum or other light metals other composite materials with other fibrous reinforcements such as graphite boron are satisfactory an alternative construction of the integral molding of the body of device 10 is to adhere with epoxy resin a one eighth inch thick polyethylene band around the grid while this reduces the strength somewhat the grid still has sufficient strength for safety purposes construction of glass fiber reinforced grates are provided under the trademark corvex u2122 by fibergrate company of dallas tex that grate may be cut to shape to provide a satisfactory unit the department of labor occupational safety and health administration o s h a 29 c f r parts 1910 permit required confined spaces for general industry states the following general requirements paragraph c 5 ii b when entrance covers are removed the opening shall be promptly guarded by a railing temporary cover or other temporary barrier that will prevent an accidental fall through the opening and will protect each employee working in the space from foreign objects entering the space permit required confined space program d the employer shall 1 implement the measures necessary to prevent unauthorized entry 3 ii isolating the permit space iii purging inserting flushing or ventilating the permit space as necessary to eliminate or control atmospheric hazards iv providing pedestrian vehicle or other barriers as necessary.