These requirements apply to factory-built gas appliances having inputs of more than 400@000 Btu per hour@ per individual combustion chamber which require flame failure and other precautions and which are intended primarily for commercial and industrial installation. The appliances covered by these requirements are gas burners@ comfort heating furnaces@ heaters and gas-fired boiler assemblies except watertube boilers having outputs of 10@000 pounds of steam per hour or more. Gas-heating equipment covered by these requirements may be operated without a competent attendant being constantly on duty at the burners while the burners are in operation. These requirements do not apply to process equipment. Other requirements are available for central-heating gas appliances@ domestic conversion burners@ floor furnaces@ room heaters@ unit heaters@ and water heaters as defined by the Standard for Installation of Gas Appliances and Gas Piping@ NFPA 54-1996. A product that contains features@ characteristics@ components@ materials@ or systems new or different from those covered by the requirements in this standard@ and that involves a risk of fire@ electric shock@ or injury to persons shall be evaluated using the appropriate additional component and end-product requirements as determined necessary to maintain the acceptable level of safety as originally anticipated by the intent of this standard. A product whose features@ characteristics@ components@ materials@ or systems conflict with specific requirements or provisions of this standard cannot be judged to comply with this standard. Where considered appropriate@ revision of requirements shall be proposed and adopted in conformance with the methods employed for development@ revision@ and implementation of this standard.