Regarding decompression diving, what is required after treatment on Table 4?

The requirement after treatment on Table 4 is a minimum 48-hour surface interval. This is crucial because Table 4 is used for managing specific decompression illness scenarios, which may involve more severe symptoms than those covered by the lower tables.

After undergoing treatment for decompression sickness, divers must allow their bodies sufficient time to eliminate any residual inert gas from their tissues, which can take longer following serious treatments. A 48-hour surface interval ensures that the diver's body has ample opportunity to recover and reduces the risk of further complications or recurrence of decompression sickness.

Considering other options, shorter surface intervals would not provide adequate time for the body to heal and might heighten the risk of additional diving-related problems or further complications should the diver attempt to dive before fully recovering. Hence, the requirement for a 48-hour surface interval emphasizes safety and the importance of allowing sufficient recovery time after an intense diving-related medical treatment.