In Oz there are regulations for different classes of explosion proof. For example if working around wheat dust the junction boxes are of a type where ventilation is possible and the lid extends quite a long way into the junction box but there is a clearance or gap between the two. If there is an explosion in the junction box the long gap between the junction box and the lid will extinguish the flame. These are normally precisely machined cast iron and made to the standards. In most situations screwed, galvanised conduit is suitable in these situations. You really need to check the standards in your country and check what is suitable according to the standards for your application.