Various types of non electrical equipment used in explosive environments formed by gases, vapors, mist and air, and/or combustible dust and air, typically do not have an effective ignition source during normal operation. However, if the moving parts of the equipment malfunction or operate abnormally, the ignition source inside the equipment can cause danger. For example, a fan, whose high-speed rotating blades are fixed to a shaft supported by rolling bearings inside the stator. During normal operation, there should be no frictional ignition source. However, due to the very small gap between the rotor and stator, faults such as bearing damage or deformation of the rotating blades, accumulation of foreign objects on the rotating blades, etc. can cause the gap to narrow and friction sparks or high-temperature surfaces to appear. In order to prevent potential ignition sources from turning into effective ignition sources under normal operation, fault, and rare fault conditions, a feasible method is to add sensors to the equipment to detect impending hazardous conditions, and initiate control measures in the early stages of condition deterioration before potential ignition sources turn into effective ignition sources. The control measures adopted can be automatically operated through a direct connection between the sensor and the ignition prevention system, or manually operated by issuing a warning to the equipment operator (with the aim of requiring the operator to take ignition prevention measures, such as stopping the equipment). In this section, in order to prevent potential ignition sources from turning into effective ignition sources, a combination of sensors and relevant automatic/manual ignition prevention measures is called a controlled ignition source type "b" protection. This type of ignition protection and devices used to achieve this purpose can take various forms. In practice, they can be mechanical, electrical, optical, visual, or a combination of the above forms. Although this section deals with ignition protection for non electrical equipment, it is still necessary to consider the fact that a large number of non electrical equipment use electrical sensors to detect and initiate measures to prevent ignition. Therefore, it is impossible for non electrical equipment protection standards not to involve the use of electrical sensors and related ignition prevention system circuits