Flaring is a common process in the oil and gas industry in which waste gases are burned and the produced energy will be wasted due to combustion. Furthermore, the results are air pollutants, as in CO, NOx, and CO2, that can have harmful impacts on the environment. To estimate and control these polluting gases, the need of an efficient and economical way to determine pollutants emissions seems to be a necessary subject. The aim of this article is to find new parametric emission factors for CO, CO2, and NOx gases by direct measurements in a pilot scale flare. The results showed that there were large variations of the emission factors in regards to flared gas composition. In addition, steam and excess air addition to gases contents showed a significant effect on emission factors values. The most important of these, which refers to the condition in which a flare works in, was crosswind effect that in high wind velocities could decrease flame destruction efficiency and, consequently, change emission factors values of pollutants. The range of observed averaged emission factors (including all flared gases compositions) for different test conditions were 0.10-0.59 kg/10(9) J, 49.0-51.6 kg/10(9) J, and 0.020-0.035 kg/10(9) J for CO, CO2, and NOx, respectively.