These requirements cover Types B and BW gas vents and Types B and BW gas vent roof jacks intended for venting gas appliances equipped with draft hoods to burn only gas. Type B vents are also intended for use with other Category I appliances that specify they are for use with Type B gas vents. Gas vents are intended for installation in accordance with the Standards of the National Fire Protection Association for Chimneys@ Fireplaces@ Vents@ and Solid-Fuel Burning Appliances@ NFPA 211 and the National Fuel Gas Code@ NFPA 54. Gas vents are also intended for installation in accordance with the Department of Housing and Urban Development Mobile Home Construction and Safety Standards@ Chapter II of 24 CFR@ Part 280 and codes such as the BOCA Basic/National Mechanical Code@ the Standard Mechanical Code@ and the Uniform Mechanical Code. A product that contains features@ characteristics@ components@ materials@ or systems new or different injury to persons shall be evaluated using the appropriate additional component and end-product requirements to determine that the level of safety as originally anticipated by the intent of this Standard is maintained. A product whose features@ characteristics@ components@ materials@ or systems conflict with specific requirements or provisions of this Standard shall not be judged to comply with this Standard. Where appropriate@ revision of requirements shall be proposed and adopted in conformance with the methods employed for development@ revision@ and implementation of this Standard. 1.3 revised December 30@ 1999