This technical report comprises the basis for a method description with regard to testing portable fire extinguishers' effective discharge time. The purpose of the project has been to find a better method of measuring than the present method for determining the discharging time, and to guarantee an objective and technically correct test. The effective discharge time is defined as the time from the instant of activation until the rate of discharge of the extinguishing medium has fallen to half the value of the maximum measured. The equipment consists mainly of an electronic load sensor and a device for collecting the extinguishing medium. The principle of the testing equipment is shown in the diagram in supplement 1. SP (the National Swedish Institute for Material Testing) have performed a series of tests covering 35 different portable fire extinguishers. The results of which have been used as a basis for establishing the limit of 50% reduction of the extinguisher medium's rate of discharge as the test criterion.