The atmosphere within an enclosed space is the number one hazard due to air contents. In order to be accessible and safe for humans to perform any kind of task within this specific space oxygen level as well as flammable/ harmful gases level should be checked prior entry.
The following hazards are related to enclosed of confined spaces
#1 Toxic Atmosphere
A toxic atmosphere may cause various acute effects, including impairment of judgement, unconsciousness and death. A toxic atmosphere may occur due to the presence or ingress of hazardous substances.
#2 Oxygen Deficiency
Oxygen can be lacking a confined space for the following reasons:
- displacement of air by another gas
- various biological processes or chemical reactions
- absorption of air onto steel surfaces, especially where these are damp
#3 Oxygen Enrichment
An excess of oxygen, in the presence of combustible materials, results in an increased risk of fire and explosion. Some materials, which do not burn in air, may burn vigorously or even spontaneously in an enriched oxygen atmosphere.
#4 Flammable or Explosive Atmospheres
A flammable atmosphere presents a risk of fire or explosion. Such an atmosphere can arise from the presence in the confined space of flammable liquids or gases or of a suspension of combustible dust in air. If a flammable atmosphere inside a confined space ignites, an explosion may occur, resulting in the expulsion of hot gases and the disintegration of the structure.
#5 Flowing Liquid or Free Flowing Solids
Liquids or solids can flow into the confined space causing drowning, suffocation, burns and other injuries. Solids in powder form may also be disturbed in a confined space resulting in an asphyxiating atmosphere.
#6 Excessive Heat
The enclosed nature of a confined space can increase the risk of heat stroke or collapse from heat stress, if conditions are excessively hot. The risk may be exacerbated by the wearing of personal protective equipment or by lack of ventilation
#7 Inadequate Lighting
Spaces may be under low lighting and crew members entering may not be able to observe properly the area near them.
In order to address and mitigate the above hazards an adequate and detailed risk assessment prior Enclosed Space Entry is vital. In this context, officers in charge need to consider and check the following:
- Ventilation prior and during entry and atmosphere checks (oxygen / toxicity)
- LEL% repeated checks; no use of electrical equipment, no hot works
- Establish communication plan (VHF/UHF); bridge to be informed at any stage of operation.
- Testing / calibration of the equipment prior use
- Hand approved safety torches and gas proof pneumatic lights safety approved
- Select proper personnel to perform the task, inform entering party during safety meeting for the space restrictions and provide clear instructions
- Team leader to be appointed; a stand by personnel and emergency response team & equipment always on scene.
- Use of anti-slippery shoes; distance inspection prior entry by an experienced crew member.
- Documented procedure for adequate inspection; calibration and maintenance of all equipment used for task with detailed checks/inspections before entry.
- Effective Drill program, specific training sessions for enclosed space entry & rescue from enclosed space.
- Continuous monitoring of operation, life lines to be used, effective emergency and rescue plan to be discussed prior operation. Rescue team to be ready for entering the space.