All conditions for entry into the duct keel, including the issue of an entry permit, must be observed. Before work is undertaken, a check should be made to ensure there is no loose scale, sludge, or hydraulic oil in the vicinity which, if disturbed or heated, could give off toxic or flammable gases.
The senior officer issuing the permit must ensure:
- Accessibility: The space should be accessible with no outwardly visible hazards, such as broken ladders, obstructions, etc.
- Ventilation: The duct should be ventilated thoroughly prior to entry. The atmosphere must be checked at different locations for:
- O₂ – 20%
- Hydrocarbon – below 1% LFL
- No toxic gases
- If the above values are not obtained, ventilation must be continued until the values are reached.
- The atmosphere must be periodically checked while personnel are in the space.
- A responsible person is to be posted at the entrance as standby.
- Communication by approved walkie-talkie or pre-arranged life-line signals should be set. The person outside must communicate periodically with the workers in the duct to ensure they are safe.
- Additional safety equipment, like spare lifelines, harnesses, flashlights, and BA sets should be kept ready.
- Proper protective clothing must be worn by all.
- Lighting should be adequate, especially at the entrance, and approved lights must be carried in.
- Resuscitators must be kept ready.
- Appropriate notices must be displayed in proper places to indicate 'men-at-work' in the compartment.
- Names and number of persons entering and exiting must be noted at the entrance to ensure everyone has come out before closing the access.
- The company's safety checklist must be filled in.
To ensure proper and effective control of operations before making an entry, a permit-to-work system should be used. This is a written system containing a step-by-step description of the work to be done and the precautions to be taken before, during, and after completion of the job.
Verbal instructions may be misheard, misinterpreted, not properly remembered, or wrongly conveyed. The permit-to-work provides an organized and predetermined safety system that includes all precautions and procedures in their correct sequence.
This procedure is required under the International Management Code for the Safe Operation of Ships and for Pollution Prevention, commonly known as the ISM Code.
The code was made mandatory in 1994 by adoption of Chapter IX to SOLAS 1974.