This Guideline applies to flares with steam injection@ which are used in chemical and petrochemical industry as well as in refineries to dispose of large quantities of combustible gases without hazard. Figures 1 and 2 are schematic illustrations of the designs of elevated flares and ground flares@ respectively. Elevated flares are generally used to burn very large quantities of gas (up to approx. 1 000 t/h) to avoid emergency situations e.g. when unforeseeable malfunctions occur in plants. They are therefore mainly built as pure safety devices. Ground flares are used for the smokeless burning of quantities of up to approx. 100 t/h of gas. They often serve as safety devices@ too@ but are also used for the controlied starting-up and closing-down of the associated production plants. They are therefore considered part of the foreseeable and regul?r plant operation@ and noise control meas? ures according to the current State of noise control technol? ogy are required as a priority. Purpose This Guideline presents characteristic noise emission values of elevated flares and ground flares. The characteristics were developed from noise emission data determined according to standardized measurement methods. The effect of noise control measures according to the cur? rent State of noise control technology is already accounted for in the characteristic noise emission values for ground flares. Notes on noise control measures for elevated flares and on the Performance of these measures are given in Annex A. This Guideline presents an aid to its users (designers@ manufacturers@ users and institutions dealing with the evaluation@ checking or monitoring of the noise emission of flares) in assessing the acoustic aspects.