Door Must Be Kept Closed at Sea Sign

Door Must Be Kept Closed at Sea Sign – MS0041

The Door Must Be Kept Closed at Sea Sign marks a weathertight or watertight door that must remain closed and secured whenever the vessel is underway, protecting the space beyond from spray, green water, and downflooding in heavy weather. This mandatory sign instructs crew that the door is not to be left open at sea and should only be opened briefly for access before being immediately re-secured.

Manufactured from durable photoluminescent material, MS0041 continues to glow after the ship’s main lighting fails, keeping the instruction legible during a blackout, heavy weather, or a night-time transit through the space. Its blue circular mandatory-action field with bold white text is designed for instant recognition at exterior and weathertight doors, supporting the IMO’s emphasis on clear, standardised shipboard signage across multinational crews.

Why the Door Must Be Kept Closed at Sea Instruction Matters

A door left open at sea is a recognised cause of downflooding casualties, particularly in heavy weather when green water or spray can enter a compartment rapidly and compromise the vessel’s stability and equipment. A clear, standardised keep-closed instruction reinforces correct deck and watchkeeping practice, reducing the chance that a door is propped open for ventilation or convenience and left unsecured before or during a passage.

Compliance and Certification

MS0041 is produced to support compliance with the vessel’s Safety Management System under the ISM Code, and weathertight and watertight door discipline is addressed within SOLAS Chapter II-1 provisions for hull integrity and subdivision. For the full regulatory text, see the IMO’s SOLAS convention overview. Maintaining clear, legible signage at every exterior door supports a positive outcome at Port State Control and flag-state inspections.

Installation Recommendations

Install MS0041 directly on or immediately adjacent to the door frame, at eye level where anyone approaching or passing through will see it clearly. Mount on a flat, stable surface using marine-grade adhesive or corrosion-resistant fasteners suited to continuous weather exposure. Confirm the sign remains legible under salt spray and UV exposure, and reinforce the instruction through deck watch handover procedures and pre-departure checks.

• Photoluminescent pictogram charges under ambient light and glows during power loss
• Bold mandatory-action blue circle format for instant multilingual recognition
• Rigid, UV-stable substrate engineered for continuous marine and weather exposure
• Compact format suited to exterior doors, weathertight openings, and deckhouse entrances
• Supports ISM Code safety-management and SOLAS hull-integrity documentation

Equip every door aboard your vessel that must stay closed at sea with the MS0041 Door Must Be Kept Closed at Sea Sign, and keep watertight and weathertight integrity compliant and reliable when it matters most.

Complete your vessel’s safety signage programme by pairing this sign with our Hazard Signs and Fire Fighting Signs ranges, ensuring full coverage across every shipboard risk area.