60.Silos: Silos used for storing dry combustible substances shall be:
(1) made of fire resistant materials;
(2) provided with covers and adequate ventilation;
(3) provided with explosion vents complying with NFPA Standard 68-1998 Guide for Venting of Deflagrations, where there is a risk of explosion. Vents already installed in silos on 2 August 2001 may also be used if they comply with a previous text of that standard and are in good working order.