Can the explosion-proof battery electric locomotive use resistor speed regulation?

There are many speed regulation methods for battery locomotives to choose from. But when the underground battery locomotive is required to be explosion-proof, resistance speed regulation cannot be selected. Why is this?

Choose an explosion-proof battery locomotive. Generally, the working environment of the electric locomotive will be in a place with a risk of explosion such as a coal mine. There are gases such as gas with different concentrations in the working environment. The process of resistance speed regulation is completed by the contact between the copper contact and the reversing drum. There is a lot of friction between the two, and electric sparks are prone to occur. Once the concentration of gases such as gas in the air reaches a certain value, an explosion is likely to occur. Therefore, for the sake of safety, there is no resistance speed regulation in the speed regulation method of the explosion-proof mining battery locomotive.

The above is why the explosion-proof mining battery locomotive cannot use resistance speed regulation.