FOREWORD This standard covers the normal and emergency venting requirements for aboveground liquid petroleum storage tanks and aboveground and belowground refrigerated storage tanks designed for operation at pressures from ? ounce per square inch (22 millimeters water column) vacuum through 15 pounds per square inch gage (1.034 bar gage). This standard does not apply to floating- or lifter-roof tanks. Engineering studies of a particular tank may indicate that use of a venting capacity other than that estimated in accordance with this standard is desirable. Section 1 of this standard applies only to aboveground non refrigerated liquid petroleum storage tanks. It outlines safe and reasonable practices for a normal temperate-zone climate and normal operating conditions. The many abnormal variables that must be considered in connection with tank venting problems make it impracticable to set forth definite simple rules that are applicable to all locations and all conditions. Larger vents may be required on tanks in which oil is heated@ on tanks that receive oil from wells or traps@ and on tanks that are subjected to pipeline surges. Similarly@ the use of flame arresters or other restrictions that may build up pressure under certain conditions may require the use of larger vents on tanks. Section 2 of this standard applies only to aboveground and belowground refrigerated liquefied hydrocarbon storage tanks. Suggested revisions are invited and should be submitted to the director of the Refining Department@ American Petroleum institute@ 1220L Street@ N.W.@ Washington@ D.C. 20005 .