Where must motors for fans that convey flammable vapors or dusts be located?

Motors for fans that convey flammable vapors or dusts must be located outside the duct to minimize the risk of ignition. Placing the motors outside ensures that any potential sparks or heat generated by the motor do not come into direct contact with the flammable materials being transported. Additionally, this configuration allows for easier maintenance and reduces the risk of fire spreading into the ductwork. It helps maintain a safer working environment by isolating the ignition source away from the flammable atmosphere within the duct. This practice aligns with safety regulations designed to mitigate hazards associated with handling volatile substances.

The other locations, such as inside the duct, at the termination point, or at the discharge, would not provide the same level of safety and could increase the risk of fire or explosion due to the proximity of the ignition source to flammable vapors or dusts.