20. The grille shall conform to the following specifications:
(1) it must be permanently bolted or equipped with a device that is designed and constructed to stop the pump and the concrete mixer as soon as it is opened;
(2) it must be designed to safely support a person weighing not less than 100 kg;
(3) the distance between the bars of the grille must not exceed 70 mm if they are parallel to one another, or 80 mm if they are arranged in a lattice design; and
(4) the distance separating the grille from the point of contact with the hopper agitator shall not be less than 75 mm.