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Confined Spaces - Safe Practise

Published: 13th Aug 2012

Operating in the hazardous and unpredictable shipping sector, IACS’s members have an admirably stringent approach to Confined Space safety practise, which they share with HSME readers in this edition.


For the purposes of clarity, there are a number of basic terms it's worth defining.

1. A confined space means a space that has any of the following characteristics:

• Limited openings for entry and exit

• Unfavourable natural ventilation

• Not designed for continuous worker occupancy

It includes, but is not limited to, boilers, pressure vessels, cargo holds, cargo tanks, ballast tanks, double bottoms, double hull spaces, fuel oil, lube oil, sewage-tanks, pump-rooms, compressor rooms, cofferdams, void spaces, duct keels, inter-barrier spaces and engine crankcases.

2. A competent person means a person with sufficient theoretical knowledge and practical experience to make an informal assessment of the likelihood of a dangerous atmosphere being present or subsequently arising in the space.

3. A responsible person means a person authorised to permit entry to a confined space and having sufficient knowledge of the procedure to be followed.

4. A Marine Chemist is a person who possesses a current Marine Chemist Certificate issued by the National Fire Protection Association (NFPA 306: Control of Gas Hazards on Vessel Sections), or equivalent.

General hazards

Work in confined and enclosed space has a greater likelihood of causing fatalities, severe injuries and illness than other types of shipyard work or onboard ships. This is also true of many other industrial settings.

The key hazards associated with confined spaces are:

• Serious risk of fire or explosion

• Loss of consciousness from asphyxiation arising from gas, fumes, vapour or lack of oxygen

• Drowning arising from increased water level

• Loss of consciousness arising from an increase in body temperature

• Asphyxiation/suffocation arising from free flowing solid (engulfment) or the inability to reach a breathable atmosphere due to entrapment Surveyors will routinely enter confined spaces that are difficult to access due to small and/or narrow openings. There may be restricted mobility. Given the usual enclosed and darkened nature of a confined space this activity ideally should not be carried out by personnel suffering from phobias (e.g. claustrophobia) or who are susceptible to panic or anxiety attacks.

Safe entry

When requested to enter a confined space only enter when a permit to enter has been issued and if you consider it is safe to do so. It is the full responsibility of the owner of the confined space to make and ensure that the confined space is safe to enter.

• The surveyor has the right to refuse to enter an unsafe and/or unknown space

• If he/she is not confident that a space is safe, he/she should report his concerns and not enter until all safety requirements are met A surveyor should not enter a space that requires use of a respirator, but may wear a respirator or escape pack if required by an owner’s policy, and only if sufficiently trained in the use of such equipment - but the space must be safe first.

• Do not enter a space first or alone

• If in doubt - do not enter - no survey is worth risking life or health for

Entering confined spaces adjacent to loaded tanks

It is important to be aware that confined spaces may be, or have been, subject to leakage from the adjacent space. The risk is that such a leakage often remains undetected because the space is not subject to regular gas measurements and ventilation. Confined spaces adjacent to loaded tanks may be entered provided the procedure for entry is completed. Spaces adjacent to cargo tanks, like cofferdams and double bottom tanks, may contain accumulated residues from previous spaces. If a tank is loaded with cargoes having a toxic vapour hazard, or with a toxic symbol in the Data Sheet, no survey should be carried out in a confined space adjacent to that tank. Be aware that toxicants produced by work (like coating, sandblasting and hydro blasting) in the area of a confined space can enter and accumulate in the confined space.

Entering confined spaces adjacent to inerted tanks

When other tanks in an inert condition are either adjacent or interconnected (e.g. pipeline) to the space to be entered, personnel should be alert to the possibility of inert gas leaking in to that space through, for example, bulkhead fractures or defective valves. The risk of this occurring can be minimised by maintaining a small but positive pressure in the space to be entered relative to the inert gas pressure. At all times the procedures on the vessel are to be followed.

Safe entry procedure

Prior to entry into an enclosed space or tank, the following should be applied: a) A Safety meeting should be held prior to the survey to discuss all aspects of safety measures including at least all items below b) Entry Permit should be obtained for the space to be entered c) Identify the hazards and assess the risks d) In order to be able to identify the hazards in the space to be surveyed and assess the risks, the following information should be available: - Latest content of the spaces to be surveyed should be identified and the content in spaces adjacent to them - For Gas Carriers: a data sheet for the last cargo should be presented - For Chemical Tankers: a data sheet for the previous three cargoes should be presented It is the owner’s responsibility to provide this information. - Check that the tank or enclosed space is empty, cleaned and ventilated

The owner is obliged to document that this is carried out. f) Evaluate need for isolation of the space g) Ensure that a standby and/or rescue team is in place h) Check and evaluate gas measurements taken - As a minimum, oxygen measurements should be carried out before entry into the enclosed space. When found necessary the measurements should be taken under the supervision of the surveyor - In addition, a set of additional control measures should be evaluated depending on what kind of tank is to be surveyed The surveyor should always use his personal gas measuring equipment during the survey. i) Evaluate need for precaution against extreme temperature j) Evaluate the lighting arrangement k) Evaluate if special clothing and/or equipment are required A checklist with the items above is recommended to be used for evaluation if the space is safe to enter. If extensive work is to be carried out within a large space, such as a cargo tank, it is recommended that a full assessment of the tank atmosphere is undertaken after the initial tests have been satisfactorily carried out and recorded. The tank atmosphere should be checked frequently during this entry, with particular attention being placed on testing the work location(s) and places that are inaccessible for testing from the deck. On satisfactory completion of this additional atmosphere test, the results should be recorded by the appropriate safety procedure in the safety management system. In relation to the entry procedure above, the following additional recommendations should be strictly enforced. Once the tank atmosphere meets the entry criteria at each sampling point, actual entry by personnel should be undertaken in two stages.

First stage

The first stage should be for the purpose of atmosphere verification and a general safety review. The personnel making the entry should be equipped with: - An emergency escape breathing set - Personal gas detector capable of monitoring at least hydrocarbon and oxygen - Portable radio - Emergency light source - A retrieval harness - An alternative means of attracting attention, e.g. a whistle

Second stage

Only after the first stage has verified that the atmosphere throughout the tank is safe for the intended task should entry for other purposes be permitted. Permit-to-work and permit-to-enter The ISM (International Safety Management) code requires the company to establish safe practises in ship operation and a safe working environment. This is commonly provided for by a permit-to-work system that is drawn up to provide a formal written safety control system. A permit-to-work will: - Set out the work to be done, the location and the precautions to be taken - Predetermine safe methods of work - Provide a clear record that all foreseeable risks have been considered - Define the precautions to be taken and their sequence - Provide written authority for the confined space to be entered and the work to start - and the time when the work must cease - Entry permit must be issued after tests have taken place to ensure that the atmosphere is safe to breathe Please note that use of non-explosion proof equipment like cameras, torches, chipping hammers, may be allowed provided that it is stated in the entry permit issued and the space is safe for hot work or safe work for workers, and LEL (Lower Explosive Limit) is measured to 0%.

Testing of the atmosphere

Initial testing should be carried out by ‘Competent Person’ or similar accredited person who will issue a certificate stating whether the space is ‘safe for man’ and/or work, and if any special conditions are to be observed. On a vessel this may be a Chief Officer or other competent person on board. If in doubt of the officer’s qualification, documentation is required to be shown. In no case should the class surveyor be considered to be a 'Competent Person' - even if he is equipped with his own personal testing equipment. Ventilation should be stopped about ten minutes before tests are made and not restarted until the tests are completed.

Testing sequence

The testing should be carried out in the following sequence:

• Oxygen-deficient or oxygen enriched atmospheres

• Flammable atmospheres

• Toxic atmospheres when considered necessary

Testing for oxygen

Any atmosphere with less than 20.8% (± 0.2%) oxygen by volume should not be entered. Oxygen measurements should be carried out by, or under supervision of, the surveyor immediately before entry into the confined space.

Testing for flammable atmosphere

A space with an atmosphere with more than 1% of the 'Lower Flammable Limit' (LFL) or 'Lower Explosive Limit' (LEL), on a combustible gas indicator should not be entered. The flammability indicator shows the percent within a safety range of 0-10% of the LEL and, ideally, should read 0%. Combustible gas detectors have normally two measuring ranges 0-100% LEL and 0-10% LEL.

Testing for toxic atmospheres

Toxins are measured in parts per million (PPM). Under no circumstances should the surveyor enter a confined space exceeding the limits specified in the table on page 23. Different testing bodies throughout the world may, however, have different acceptance limits. For vessels with inert gas systems, trace amounts of various toxic gases may increase the hazard of exposure for personnel. Normally, a steady 21% by volume of oxygen reading will be sufficient to dilute these gases to below their 'Threshold Limit Value' (TLV). Remember - never trust one’s own senses to determine if the air in a confined space is safe. Many toxic gases and vapours can neither be seen nor smelled, nor can the level of oxygen present be determined. Be aware that some chemicals have a lower TLV value than odour value. Gases from these substances will not be traceable by smell before they are dangerous to health.

Preparation for entering confined spaces- ventilation

Ventilation should be continuous where possible because in many confined spaces the hazardous atmosphere will form again when the flow of air is stopped. All openings should be opened for ventilation including emergency exit. De-ballasting a tank does not guarantee a safe atmosphere. Testing of the atmosphere is still required. The inert gas fans should not be used to provide fresh air ventilation because contaminants from the inert gas lines could be introduced into the tanks.

Isolation of space

The surveyor should evaluate the need for isolation of the confined space from service before entering the space. The surveyor should not enter or remain in any ballast or cargo tank if ballast is transferred into or out of any tank, if not agreed beforehand.


A standby person should be assigned to remain on the outside of the confined space and be in constant contact (visual or two-way voice communication e.g. walkie-talkie) with the survey team inside. Routines for communication intervals with the survey team should be established. The standby person: - Should not have any other duties than to serve as standby and know who should be notified in case of emergency - Should never leave his post even after help has arrived and is a key communication link to others onboard - Should be able to communicate sufficiently in a relevant common language Communication between watch personnel and standby person should be established. Rescuers must be trained in and follow established emergency procedures and use appropriate equipment and techniques, such as lifelines, respiratory protection, standby persons. Emergency and evacuation procedures should be agreed and understood by all parties involved in a potential rescue operation. Steps for safe rescue should be included in all confined space entry procedures. Rescue should be well planned and evidence should be made available that indicates drills have been frequently conducted on emergency procedures. Unplanned rescue, such as when someone instinctively rushes in to help a downed co-worker, can easily result in a double fatality or even multiple fatalities if there is more than one would-be rescuer. More than 50% of the workers in confined spaces die while attempting to rescue other workers. As such, an unplanned rescue could be the last.

Personal Protection Equipment (PPE)

PPE is traditionally regarded as the last line of protection, with the emphasis being placed on avoidance and appropriate managerial control methods. The potentially hazardous nature and isolated position of those entering a confined space, however, means that for the surveyor, PPE may be the first line of protection. Each confined space will present different hazards and degrees of risk to health and safety. The final provision of PPE should therefore be based on an assessment of risk. Basic surveyor PPE should include: - Body protection: hard wearing overalls with suitable pockets for notebook - Foot protection: steel toecaps (200 joules), steel midsoles, good grip, oil resistant - Head protection: hard hat with chinstraps - Hand protection: hard wearing gloves - Eye protection: protective glasses, goggles - Ear protection: ear defenders or ear plugs - worn subject to communication system - Gas meter: multi-gas meter for measuring of HC, H2S, CO, O2 is recommended - Lighting: hand held with lanyard and appropriate beam width

Published: 13th Aug 2012 in Health and Safety Middle East

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