What is permissible to operate when a train is laid up in a repair yard due to lost compressed air?

When a train is laid up in a repair yard due to lost compressed air, the operation of certain systems is critically evaluated based on safety and functionality. The fans are permissible to operate because they typically do not rely on compressed air to function. Their role is essential for ventilation and maintaining a comfortable environment within the train, especially when it is stationary for repairs.

Lights and doors often depend on the availability of electrical systems or compressed air, particularly in systems designed for automatic operation. The brakes, being a crucial safety mechanism, require proper pressure to function correctly; without compressed air, they cannot be safely operated. Therefore, the operation of fans is appropriate and acceptable under these conditions, aligning with safety protocols while the rest of the systems remain inoperable due to the lack of compressed air.