According to the IMO standard, what is the maximum blood alcohol concentration allowed?

• A. 0.04
• B. 0.00
• C. 0.10
• D. 0.08

Answer: (D)

Blood alcohol concentration measures how much alcohol is in the blood, and even small amounts can dull judgment, slow reaction times, and impair coordination—things you need to avoid when keeping a vessel safe. The IMO standard sets a maximum BAC for personnel on watch at 0.08 percent. This threshold is used because it represents a balance between safety and practicality, acknowledging that some impairment can begin near that level while still allowing for everyday tolerance limits in various regions. Values lower than that (0.04) are stricter than the standard, 0.00 would be zero tolerance (not the official maximum), and 0.10 is above the allowed limit and would indicate a higher risk of impairment.