Final answer:
The duration before controlling operations depends on the substance's half-life and specific industry regulations, which are not provided in the question. However, general health guidelines suggest that enough time must be allowed for the body to metabolize and eliminate the substance to prevent impaired performance.
Step-by-step explanation:
The question concerns guidelines for how long controllers, such as those involved in air traffic control, must abstain from using drugs that can affect the central nervous system and impact alertness, judgment, vision, and consciousness. While the exact time required may depend on specific industry regulations or the half-life of the particular substances involved, general health guidance on the metabolism of substances like alcohol suggests that it's important to allow the body enough time to process and eliminate these drugs to prevent impaired performance. It is known that certain drugs, including alcohol, can have effects that last several hours, and factors such as the drug's half-life play a role in determining how long these effects can persist. However, without clear industry-specific guidelines provided in the question, a precise answer indicating whether it should be 24, 48, 72, or 96 hours cannot be accurately provided.