Entering enclosed spaces is one of the most dangerous operations onboard ships, and tragically, many fatal accidents have occurred due to oxygen deficiency, toxic gases, or a lack of proper procedures. This blog post outlines general procedures, precautions, and best practices for safe enclosed space entry, applicable to all mariners.

⚠️ What Is an Enclosed Space?
An enclosed space is any space with limited openings for entry/exit, inadequate ventilation, and is not designed for continuous occupancy. These characteristics make them extremely hazardous to personnel.

Examples include:

Cargo holds: Large, poorly ventilated spaces that can contain cargo residue or dangerous gases.
Double Bottom Tanks (DBTs) and Ballast Tanks: Often contain inert gas, rust, or silty deposits that can release toxic gases.
Void Spaces and Cofferdams: Used to provide clearance between compartments and can accumulate gases or be oxygen-deficient.
Pump Rooms: May contain fuel vapors, chemicals, or hydrogen sulfide (H2S) from bilge water.
Fuel or Oil Tanks: Pose risks of fire and poisoning from hydrocarbon vapors.

🔍 Hazards of Enclosed Spaces
Understanding the risks is crucial for preventing accidents:

Oxygen Deficiency (<19.5): The most common cause of fatalities. Oxygen can be displaced by other gases or consumed by corrosion, organic decay, painting, or welding operations. Symptoms include rapid breathing, accelerated heart rate, dizziness, weakness, and eventually loss of consciousness and death.
Toxic Gases (e.g., H2S, CO, CH4, benzene):
Hydrogen Sulfide (H2S): Often found in sewage, decaying organic matter, and petroleum products. At low concentrations, it smells like rotten eggs, but at high concentrations, it quickly dulls the sense of smell and can lead to immediate loss of consciousness and death.
Carbon Monoxide (CO): A colorless, odorless gas produced by incomplete combustion. It binds to hemoglobin in the blood, preventing oxygen transport.
Methane (CH4): A flammable gas that can also displace oxygen.
Benzene: A toxic, carcinogenic hydrocarbon often found in fuel tanks.
Flammable Atmospheres: Vapors from fuel, gases, or volatile organic compounds can form explosive mixtures with air. An ignition source, even a spark from a tool, can lead to a catastrophic explosion.
Physical Dangers:
Slips and Falls: Due to wet or slippery surfaces, oily residues, or unstable ladders.
Poor Lighting: Can obscure hazards, hinder navigation, and increase the risk of falls.
Falling Objects: Tools or materials can fall from heights.
Mechanical Hazards: Unexpected movement of machinery, exposed moving parts.
Sudden Gas Releases: Gases can be trapped in deposits, and their sudden release when deposits are disturbed can rapidly alter the atmosphere.

✅ Entry Preparation Checklist
Thorough preparation is your best defense. Follow a structured risk assessment and preparation process:

Risk Assessment:
Identify specific hazards: Conduct a detailed investigation of the space's history (what it contained, when it was last entered).
Evaluate required PPE and emergency procedures: Determine all necessary equipment, from protective clothing to communication devices, and ensure everyone is trained to act in an emergency.
Permit to Work (PTW):
Issue a dedicated “Enclosed Space Entry Permit”: This is not just a formality. It's an official document confirming that all necessary safety measures have been taken and verified.
Must be approved and signed by Master/Chief Officer: This ensures that senior management is aware of and accountable for the safety of the operation.
Atmosphere Testing (performed from outside):
Oxygen (O2) – must be 20.9: This is the normal oxygen level in the air. Any deviation indicates a potential hazard.
Flammable gas (LEL) – must be <1: Exceeding this value indicates an explosive atmosphere.
Toxic gases (e.g., H2S, CO) – must be 0 ppm: Any presence of these gases is extremely dangerous.
Use multi-gas detectors (Dräger, MSA, etc.): These devices are specifically designed to measure multiple gases simultaneously and have audible alarms.
Continue monitoring during entry: The atmosphere can change, so continuous monitoring is vital.
Ventilation:
Ventilate the space thoroughly before and during entry: Use powerful blowers for forced ventilation or ensure natural draft if possible. The goal is to create a safe and breathable atmosphere.
PPE & Equipment:
Safety harness and lifeline: Must be worn by the entrant and attached to the standby person outside. This allows for retrieval in case of an emergency.
Portable gas detector with audible alarm: Must be carried by the entrant for continuous monitoring of the atmosphere.
Communication equipment (radio or talk-back): Ensures constant contact between the entrant and the standby person.
Emergency SCBA (Self-Contained Breathing Apparatus) near entry point: Must be ready for immediate use by the standby person in case a rescue is needed.
Explosion-proof lighting: Standard lighting can be an ignition source in a flammable atmosphere.
Rescue Plan:
Designate a standby person at the entrance: This person must under no circumstances enter the enclosed space. Their role is to observe, maintain communication, and raise the alarm.
Ensure team trained for immediate rescue: There will be no time for training in an emergency. Regular drills and exercises are critical.
SCBA and stretcher available: Must be easily accessible and ready for use.

👷 Personnel Required
Each team member plays a critical role in ensuring safety:

Entrant: The person entering the space to perform the work. Must be fully aware of the hazards and procedures.
Attendant (Standby Person): Stays outside, constantly monitors the entrant, maintains communication, and is responsible for raising the alarm and coordinating rescue efforts if needed. Must never enter the space for rescue!
Permit Issuer: The Chief Officer or Master, responsible for assessing risks and issuing and canceling the Permit to Work.
Gas Tester: A certified officer trained and competent in using gas detectors and interpreting readings.

🕒 While Inside the Space
Even after thorough preparation, remain vigilant:

Maintain constant communication: Regularly report your condition and location to the standby person.
Keep gas monitor active: Continuous monitoring is vital.
Minimize time spent inside: Work efficiently to reduce exposure to potential hazards.
Exit immediately if alarm activates: Do not attempt to find the source of the problem. Your safety is paramount.

📝 After Completion
Proper completion of the operation is also important:

Cancel the Permit to Work: This confirms that the operation is complete and the space is either safe or access to it is closed.
Record entry in the Logbook or SMS (Safety Management System): This ensures accurate records of all operations and their conditions are kept.
Report any unsafe conditions or findings: If any new hazards or issues were discovered, they must be immediately reported for corrective action.

🧠 Best Practices & Tips
These principles should become second nature:

-Never enter alone: There must always be a standby person outside.

-Never trust your senses — always test first: Many dangerous gases are odorless or colorless. Your senses are unreliable in this context.

-Never skip the Permit to Work process: It's not just bureaucracy; it's a vital risk management tool.

-Stay updated with regular enclosed space drills: Practice makes perfect. Regular drills help reinforce procedures and skills.

-Check company-specific training and requirements: Each shipping company may have its own specific procedures and additional equipment. Be sure to familiarize yourself with them.

Do you have any questions or want to share your experience? Leave your comments below!