No explosives, poisons, acids or gases, of which the vehicle transporting the same is required to bear the markings mentioned in § 91.40, may be transferred from one vehicle to another except in case of breakdown or collision, and then only after notifying and under the supervision of the Police and Fire Departments. However, this section shall not be so construed so as to prohibit the transfer, pickup or delivery of articles or materials, the storage of which is permitted.
