The Core STCW and MLC Rest Requirements
The regulations approach fatigue by mandating minimum hours of rest, rather than setting a cap on working hours. All crew members, from deck cadets to the Master, are legally bound to these limits.
The two golden rules are: A seafarer must receive a minimum of 10 hours of rest in any 24-hour period. Furthermore, they must receive a minimum of 77 hours of rest in any 7-day period.
The 24-Hour Look-Back and Split Periods
The 24-hour limit is not based on a calendar day (midnight to midnight). It is a 'rolling' window. Port State Control software evaluates every single hour of the day and looks forward and backward 24 hours to ensure 10 hours of rest exist.
Because watchkeepers (like mates and engineers) work on rotating schedules (e.g., 4 hours on, 8 hours off), the 10 hours of rest do not need to be consecutive. However, the law limits how the rest can be split: It can be divided into no more than two periods, one of which must be at least 6 hours in length. The interval between consecutive periods of rest cannot exceed 14 hours.
How to Audit Rest Hours
Auditing rest hours involves analyzing the vessel's official timesheet grid. Every hour of work counts against the minimums.
Worked Example: A Second Officer stands watch from 00:00-04:00 and 12:00-16:00. This is 8 hours of work. The rest periods are 04:00-12:00 (8 hours) and 16:00-00:00 (8 hours). Total rest = 16 hours. This complies with the 10-hour rule. It is split into two periods, and one is at least 6 hours long. The interval between rests is 4 hours of work (under the 14-hour max). Assuming they work this exact schedule 7 days a week, their total weekly rest is 16 x 7 = 112 hours, easily clearing the 77-hour weekly minimum.
Exceptions, Emergencies, and Drills
The reality of shipping means perfect schedules are often interrupted by mandatory safety drills, mooring operations, or emergencies.
In a true emergency (e.g., firefighting, rescuing another vessel), the Master has the authority to suspend rest hour regulations until the situation is secure. Mandatory safety drills must be conducted in a way that minimizes disturbance to rest periods. STCW does contain 'Exception' clauses (like the Manila Amendments) that allow temporary reduction of the 10-hour rule to 9 hours under extreme restrictions, but these require specific Flag State approval and are heavily scrutinized.
Frequently asked questions
What happens if a Port State Control inspector finds rest hour violations?
A PSC inspector can issue deficiencies that the vessel must correct. If systemic, falsified, or severe violations are found (suggesting a dangerously fatigued crew), the vessel can be legally detained in port until compliance is restored.
Are meal breaks considered work or rest?
Short breaks (typically under 30 minutes) or meal times are generally not counted as rest periods under STCW/MLC calculations. A rest period must be a continuous, uninterrupted block of time where the seafarer is off-duty.
What happens if a drill interrupts my 6-hour sleep period?
If a seafarer's rest is disturbed by a call-out to work (like an unannounced drill), they must be provided with an adequate compensatory rest period. If the interruption breaks the minimum 6-hour block requirement, it creates a non-compliance that must be managed.
Is the Master (Captain) exempt from rest hours?
No. The Master is legally required to comply with rest hour regulations, though their schedule is often the most erratic. If the Master is constantly exceeding work limits due to administrative burden, the ship is technically unseaworthy due to fatigue risk.