TRAINING IN THE USE MANUALLY OPERATED METAL GAS VALVES, GAS REGULATORS, AUTOMATIC GAS VALVES, SAFETY ACCESSORIES FOR GAS PIPES, NAMELY, CHECK VALVES, FLASH-BACK ARRESTORS AND SHUT-OFF VALVES, AND ELECTRONIC APPARATUS FOR THE DELIVERY OF NITRIC OXIDE FOR INHALATION IN CONSTANT CONCENTRATION AND IN SYNCHRONIZED PROPORTIONS AND FOR MONITORING SAID DELIVERY