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May 2001


Much has been written on this subject and yet many seafarers families suffer loss due to death in enclosed spaces. The tragedy is that most of these deaths can be prevented by the application of simple procedures and precautions. It is, therefore, of the utmost importance that the precautions applying to entry into enclosed spaces are understood by everybody on board. Any tank or other space, enclosed or not, that has been isolated from the surrounding atmosphere for a period of time must considered as dangerous. Enclosed spaces include the following:-



Cargo holds

Pump rooms

Ballast tanks

Void spaces

Peak tanks


Bunker tanks

Fresh water tanks

Pipe tunnels

Duct keels


and any other spaces which are normally kept closed.

The above spaces should never be entered without explicit instructions from the Master or a Senior Responsible Officer. Before giving permission to enter the Master or Senior Responsible Officer must ensure all precautionary measures have been taken.



Shortage of Oxygen – this affects the brain faster that any other part of the body. As the oxygen content of the atmosphere falls below 21% breathing become faster, deeper and more laboured. The amount of impairment will vary for each individual and some will become unconscious. Below 16% the brain is quickly affected and below 10% unconsciousness is inevitable and the individual will die if not resuscitated and removed to fresh atmosphere. At oxygen levels below 5% unconsciousness is immediate and irreversible brain damage occurs.




Ventilation must be carried out before entry is permitted into any enclosed spaced. Forced ventilation - at least two air changes must take place before entry is made. Natural ventilation - the space should be allowed to breath for at least 24 hours.

In certain spaces, such as double bottom tanks, the most effective way of ensuring full ventilation may be to fill the compartment with clean seawater and then pump it out. Regardless of the method employed, no entry must be made until tests have shown that the area inside the atmosphere is breathable - contains 21% oxygen and no noxious hydrocarbon or other toxic gases.


Gas Testing


No entry should be made into any enclosed space unless the atmosphere inside has been tested and found to contain sufficient oxygen. Oxygen is depleted by oxidisation (rusting) of steel – be very aware that tanks containing amounts of rusty coloured water are highly dangerous. The first test for all ships should be to ensure the atmosphere throughout the space contains 21% of oxygen by volume. (Note: 19% oxygen may be breathable but it is not "Safe".)

The second test, when necessary, should be to ensure that no hydrocarbon gases are present and zero readings on explosimeters are obtained. However, it should be remembered that Carbon Monoxide, inert gas (Tankers), exhaust fumes (Car Carriers) and Methane (formed by rotting vegetable/animal products in dirty bilge/ballast water) may also be present and are not life supporting. Before entry is permitted, the Master or a Senior Responsible Officer must ensure that tests have been made by a competent individual for these and any other gases which may be considered applicable.


Entry Procedures


No-one should enter an enclosed space without the Master’s or Senior Responsible Officer’s signed consent on a Company approved form or "Check List". Further, individuals should never enter enclosed spaces alone unless a watchman stationed at the entrance of the compartment, the "linkman", is in continuous communication with the man in the tank and the emergency support co-ordinator (officer on the bridge at sea or the officer on watch in the engine room).


An Enclosed Space Entry Check-List


This check-list must be completed by the Responsible Officer in charge and must always be approved and countersigned by the Master. A separate check-list should be completed for each and every entry operation and should include the following details.

  1. Spaces to be entered.
  2. Reasons for entry. 
  3. Entry and exit points.
  4. Results of atmosphere checks.
  5. Names of persons entering.
  6. Times of entry and expected duration.
  7. Method and frequency of communication.
  8. Name of the linkman.
  9. At least one compressed air breathing apparatus set must be positioned at the point of entry together with a resuscitation unit and rescue equipment consisting of life-lines and harnesses.
  10. The Co-ordinator is on duty to sound the emergency alarm without delay if a problem occurs.
  11. Details of ventilation method.
  12. Personal oxygen meters are issued - if available.

Note: Entry into a space that is not gas freed or does not contain 21% oxygen must never be undertaken by a crew member – except in an emergency to save life and only when using a breathing apparatus and with full back up/ support party.


Duties of the Master


The Master is personally responsible for the safety of every man entering an enclosed space. As this is a potentially dangerous act, he must ensure before signing the entry into enclosed space form that he is satisfied that it has been properly ventilated, that the atmosphere in the space has been properly tested (with the appropriate instruments at different levels for oxygen and/or other gases) and that the people carrying out the tests are competent to do the job. He must also ensure that a "Responsible Officer" is in charge of the operation.


Responsibilities of the Officer in Charge


He must ensure that the space has been found safe, that the necessary lines of communication and equipment are in place so that in the event of trouble inside the space, the emergency party are able to respond quickly and safely to evacuate the people inside.

He must ensure communications between the people inside the tank and those on stand-by outside the tank have been established and that a co-ordinator is monitoring the situation from a place where alarms can be raised to send in the emergency team.




On no account should the linkman attempt to enter it before additional help has arrived, and no-one should enter any space or attempt to rescue without wearing a breathing apparatus set and a rescue harness. All too often a casualty in an enclosed space has caused the linkman to rush into the space in an attempt to effect a rescue, often with fatal results, so that when the rescue party arrives they are then confronted with two casualties and double the problems. The Master or Responsible Officer should make sure that people who have been given rescue duties and responsibilities are competent in the use of breathing apparatus sets and have been trained and drilled in enclosed space entry. Regular drills should be undertaken simulating rescue of incapacitated people from dangerous spaces and details recorded in the official log book.


Entry Drills


Whilst a statutory duty to practice emergency drills simulating the rescue of a crew member from a dangerous space may not apply to all ships and all flags, such drills are certainly in the interests of shipboard safety. Drills should be held at regular intervals (not exceeding two months) and recorded in the official log book. These drills can range from "table top drills" in which the procedures are enacted and discussed, to a full-scale emergency drill to retrieve a dummy from a tank or compartment.


Responsibilities of the Shipowner


It is in the interest of the Shipowner that procedures for ensuring the safe entry and working in dangerous spaces are clearly laid down and that the Master, as the shipowner’s agent, ensures that such procedures are observed on board the ship.


Permits to Work


This article has addressed those procedures required for entering enclosed spaces. This subject will be developed in a future article concerning permits to work