Structured Safety - Confined space entry as a hazardous activity

Structured Safety - Confined space entry as a hazardous activity

Confined space (CS) entry has been recognised as a hazardous activity for many years and yet, sadly, it continues to be a source of major accidents and incidents resulting in fatalities and severe environmental pollution around the world.

When you search online, there are a number of examples of fatal CS-related accidents. You may be familiar with such incidents, either as first-hand experience or from colleagues.

As examples:

  • Four people died when entering a sewage pit for cleaning as a result of trying to rescue the first entrant who got into difficulties (Gulf News, 2015)
  • Three people were killed in ADCO onshore oilfield H2s accident

    What is a confined space?

    Although a straight forward question, the definition differs from country to country. But the essential features of a confined space such as enclosed space, risks and differentiation from other parts of the establishment are common to all.

    For example, under the Abu Dhabi OSHAD (CoP 27) Code of Practice V3.1 March 2019, and the UK HSE Approved Code of Practice (L 101), a confined space is defined as “any place, including tanks, vessels, pipes, sewers, silos, storage bins, hoppers, vaults, pits, excavations, manholes or other similar space that by the virtues of its enclosed nature, there arises a reasonably foreseeable specified risk”.

    Under OSHA 3138-01R Standard, a CS is defined as somewhere that:

  • Is large enough for an employee to enter fully and perform assigned work
  • Is not designed for continuous occupancy by the employee
  • Has a limited or restricted means of entry or exit These spaces may include underground vaults, tanks, storage bins, pits and diked areas, vessels, silos and other similar areas.

    Furthermore, the OSHA standard narrows it down to Permit Required type of Confined Space (PRCS) as follows:

  • Contains or has the potential to contain a hazardous atmosphere
  • Contains a material with the potential to engulf someone who enters the space
  • Has an internal configuration that might cause an entrant to be trapped or asphyxiated by inwardly converging walls or by a floor that slopes downward and tapers to a smaller cross section
  • Contains any other recognised serious safety or health hazards

    Confined space locations

    Some features of a confined space are not obvious at first glance. For example, when entering a space enclosed on three-sides by land but open to the sky it may not seem like a CS.

    There are, however, recorded fatalities in such spaces in the farming industries or by the side of canals where the level of oxygen may be below the safe limits due to displacement by biological plant/animal activities, which could release low-lying carbon dioxide or hydrogen sulphide.

    The more common locations of a confined space are listed below based on L 101 UK HSE guidance referenced in Section 3. Note that the list is not exhaustive. If your specific CS does not appear on this list, it does not mean

    it is not a confined space. For more information, details of how to identify a CS are provided in Section 8 of the HSE guidance.

    Examples of confined space locations include:

  • Ducts, culverts, tunnels, boreholes, bored piles, manholes, shafts, excavations and trenches, sumps, inspection and under-machine pits, cofferdams
  • Freight containers, ballast tanks, ships’ engine rooms and cargo holds
  • Buildings, building voids
  • Some enclosed rooms (particularly plant rooms) and compartments within
  • Enclosures for the purpose of asbestos removal
  • Areas used for storage of materials that are likely to oxidise (such as store rooms for steel chains or wood pellet hopper tanks)
  • Unventilated or inadequately ventilated rooms and silos
  • Structures that become confined spaces during fabrication or manufacture
  • Interiors of machines, plant or vehicles

    As a reminder, there may be other types of confined space not covered in the previous list.

    Hazards of confined spaces entry

    The more common hazards of a confined space are listed as:

  • Presence of flammable or oxygen rich environment
  • Presence of toxic and/ or corrosive substances
  • Lack of oxygen or depleted levels of oxygen
  • Presence of asphyxiants
  • Thermal load (hot or cold)
  • Working at height
  • Unexpected ingress of other substances or water
  • Other hazards such as electricity, noise, collapse or subsidence of or within the space, loss of structural integrity and those arising from mechanical equipment and working space
  • Hidden presence of toxic, corrosive or flammable substances below apparently dry films such as previous tank coating, which during cleaning processes become live and emit the trapped substances

    Modern Standards and Regulations

    Countries around the world have their own safety standards on CS entry requirements. Examples for the Middle East, Europe, Australia and USA, respectively, are listed below:

  • 27.0 - Confined Spaces v3.1 English- Updated available at OshadSystemDocument/Attachments/122/OSHAD-SF%20-%20TG%20-%20 Safe%20Work%20in%20Confined%20Spaces%20v3.1%20English.pdf
  • Safe Work in Confined Spaces (
  • Model Code of Safe Working (Confined Spaces available at: www.safework
  • OSHA (29 CFR 1910.146) Confined Spaces and Permit-Required Confined-Spaces OSHA 3138-01R (2004) (

    This is not an exhaustive list and some situations would present additional or multiple simultaneous hazards such as ergonomic hazards whilst carrying out detailed maintenance in confined spaces with power tools.