Under what condition must crew members avoid performing duties?

Crew members must avoid performing their duties when they have consumed alcohol less than 8 hours prior to the reporting time. This guideline is rooted in safety regulations designed to ensure that crew performance is not impaired. The 8-hour timeframe is a standard industry rule where individuals are advised to have no alcoholic beverages leading up to the start of their work schedule.

It's important to maintain a clear mind and the ability to respond effectively in operational environments, and consuming alcohol can significantly hinder these abilities. The focus on this timeframe emphasizes the need for personal responsibility and adherence to safety standards that prioritize both crew and passenger safety.

In contrast, the other options suggest different parameters regarding alcohol consumption and blood alcohol concentration levels, which do not align with the appropriate guidelines for aviation crew members. Maintaining a clear distinction through the 8-hour rule reinforces the industry's commitment to safety and responsible conduct among crew members.