Spaces that have not been tested should be considered unsafe for persons to enter. If the atmosphere in an enclosed space is suspected or known to be unsafe, the space should only be entered when no practical alternative exists, the Republic of Liberia highlights in a recent Marine Notice which provides advice on entering enclosed spaces onboard.
To remind, as enclosed space is considered a space which has limited openings for entry and exit; inadequate ventilation; and is not designed for continuous worker occupancy. It includes, but is not limited to, cargo spaces, double bottoms, fuel tanks, ballast tanks, cargo pump-rooms, cargo compressor rooms, cofferdams, chain lockers, void spaces, duct keels, inter-barrier spaces, boilers, engine crankcases, engine scavenge air receivers, sewage tanks, and adjacent connected spaces. [ This list is not exhaustive and a list should be produced on a vessel-by-vessel basis to identify enclosed spaces.]
The instructions and procedures should ensure that entries into enclosed spaces are carried out in a safe manner
What is more, the company should ensure that a risk assessment is conducted to identify all enclosed spaces on board the vessel. This risk assessment should be dynamic and periodically validated. In order to ensure safety, a competent person should always make a preliminary assessment of any potential hazards in the space to be entered.
The assessment should take into account current and previous cargo carried, safety restrictions related to treated ballast in the ballast water management plan, fumigation, inert gas, ventilation of the space, coating of the space and other relevant factors. The competent person’s preliminary assessment should determine the potential for the presence of an oxygen-deficient, oxygen-enriched, flammable or toxic atmosphere.
The competent person should bear in mind that the ventilation procedures for an adjacent connected space may be different from the procedures for the ventilation of the enclosed space itself.
The master or the responsible person should determine that it is safe to enter an enclosed space by ensuring that:
- potential hazards have been identified in the assessment and as far as possible isolated or made safe;
- the space has been thoroughly ventilated by natural or mechanical means to remove any toxic or flammable gases and to ensure an adequate level of oxygen throughout the space;
- the atmosphere of the space has been tested as appropriate with properly calibrated instruments to ascertain acceptable levels of oxygen and acceptable levels of flammable or toxic vapors;
- the space has been secured for entry and properly illuminated;
- a suitable system of communication between all parties for use during entry has been agreed and tested, including alternate means of attracting attention;
- an appropriate means of rescue has been evaluated and agreed taking into account the nature and construction
- of the enclosed space and the rescue and resuscitation equipment available;
an attendant has been instructed to remain at the entrance to the space whilst it is occupied; - rescue and resuscitation equipment has been positioned ready for use at the entrance to the space and rescue arrangements have been agreed;
- personnel are properly clothed and equipped for the entry and subsequent tasks;
- a permit has been issued, authorizing entry; and
- vessel’s crew should be made aware of such operations in order to avoid accidents resulting from unauthorized use of equipment, valves, stopping the ventilation or closing of ventilators.
Precautions during Entry
The atmosphere should be tested frequently whilst the space is occupied and persons should be instructed to leave the space should there be deterioration in the conditions. Persons entering enclosed spaces should be provided with calibrated and tested portable multi-gas detectors that monitor the levels of oxygen, carbon monoxide, hydrogen sulphide and other flammable/toxic gases or vapours (% of LFL) as appropriate.
Ventilation should continue during the period that the space is occupied and during temporary breaks. Before re-entry after a break, the atmosphere should be re-tested. In the event of failure of the ventilation system, any persons in the space should leave immediately.
Particular care should be exhibited when working on pipelines and valves within the space. If conditions change during the work, increased frequency of testing of the atmosphere should be performed. Changing conditions that may occur include increasing ambient temperatures, the use of oxygen-fuel torches, mobile plant, work activities in the enclosed space that could evolve vapors, work breaks, or if the vessel is ballasted or trimmed during the work.
In the event of an emergency, under no circumstances should the attending crew member enter the space before help has arrived and the situation has been evaluated to ensure the safety of those entering the space to undertake rescue operations. Only crew members with enclosed space entry or rescue responsibilities should perform rescue operations in enclosed spaces.
Additional precautions for entry into a space where the atmosphere is known or suspected to be unsafe
In spaces where the atmosphere is suspected to be hazardous, entry should only be made for further testing, essential operation, safety of life or safety of a vessel. The number of persons entering the space should be the minimum compatible with the work to be performed.
In addition, the following should be taken into consideration:
- Suitable breathing apparatus, e.g. of the air-line or self-contained type, should always be worn, and only personnel trained in its use should be allowed to enter the space.
- Air-purifying respirators should not be used as they do not provide a supply of clean air from a source independent of the atmosphere within the space.
- Emergency Escape Breathing Devices (EEBDs) should not be used for entering oxygen deficient spaces, as these are used only for escaping from a compartment that has a hazardous atmosphere, although spare EEBDs may be available at location in the enclosed space for emergency escape, when necessary.
- Persons entering enclosed spaces should be provided with calibrated and tested portable multi-gas detectors that monitor the levels of oxygen, carbon monoxide, hydrogen sulphide and other flammable/toxic gases or vapours (% of LFL) as appropriate.
- Rescue harnesses should be worn and, unless impractical, lifelines should be used.
- Appropriate protective clothing should be worn, particularly where there is any risk of toxic substances or chemicals coming into contact with the skin or eyes of those entering the space.
