Aim\ To offer the basis to design electrical equipment for separating explosion. Methods\ A method of test for ascertainment of the maximum experimental safe gap of combustible gases or vapors is presented. Based on this method
the experimental results with several combustible gases(or vapors)are obtained. Results\ The tested data are close to the IEC standard. Conclusion The maximum allowable structure gap of electrical equipment for separating explosion must be less than the maximum experimental safe gap.