Work safely in confined spaces on drainage projects

If your construction work involves entering manholes, sewers, inspection chambers, pumping stations, valve chambers, or service ducts, you must comply with the Confined Spaces Regulations 1997 (CSR 1997). These regulations impose strict duties because confined space entry is one of the most dangerous activities in the construction industry.

Drainage confined spaces present specific hazards that can kill without warning. Toxic gases such as hydrogen sulphide build up from decomposing organic matter in sewers. Oxygen levels can drop below safe limits in enclosed chambers. Water levels can rise suddenly from upstream discharge or storm events. Every year, workers are killed or seriously injured in drainage confined spaces — often because basic precautions were not followed.

Non-compliance is a criminal offence carrying an unlimited fine and up to 2 years’ imprisonment on indictment. Work in confined spaces also falls within CDM 2015 Schedule 3 particular risks, meaning your construction phase plan must specifically address these hazards.

Determine whether entry can be avoided

Your first legal duty under Regulation 4(1) is to avoid entering a confined space unless entry is not reasonably practicable. Before planning any entry, consider whether the work can be done without anyone going inside, for example by CCTV survey of sewer and pipe condition, high-pressure jetting to clear blockages, remote sensors for water level, flow or gas, or redesigning the work so repairs are carried out from outside.

If any alternative is reasonably practicable, you must use it. Document your assessment of alternatives and the reasons entry is necessary before proceeding.

Carry out a confined space risk assessment

Where entry cannot be avoided, you must carry out a suitable and sufficient risk assessment specific to the confined space and the work to be done. A generic risk assessment is not adequate — each confined space has different characteristics and hazards.

Your risk assessment must identify:

• The type and dimensions of the confined space (manhole, sewer, chamber, duct)
• The hazards present or likely to arise (gases, oxygen depletion, drowning, engulfment, temperature)
• The work to be carried out and its duration
• The number of people who will enter
• The equipment needed for safe entry, work, and rescue
• Previous incidents or known risks at the location
• Weather conditions and upstream activities that could affect the space

The risk assessment must be carried out by a competent person with knowledge of the specific hazards in drainage confined spaces. Review and update the assessment whenever conditions change.

Establish a safe system of work

Regulation 4(2) requires you to establish a safe system of work that makes work in the confined space without risk to health, so far as is reasonably practicable. Your safe system must cover every stage from preparation through to exit, and must include:

• a competent supervisor who controls and oversees the entry
• isolation of services, locking off pumps, valves and upstream flows to prevent flooding or the release of harmful substances
• forced ventilation to keep the atmosphere breathable throughout the work
• continuous monitoring for oxygen, hydrogen sulphide, methane, carbon monoxide and carbon dioxide with a calibrated multi-gas detector
• constant contact between the entrant and the attendant outside
• a maximum entry time based on conditions and physical demands
• personal and respiratory protective equipment suited to the hazards identified

Test the atmosphere before anyone enters, using a remote sampling probe lowered into the space. Do not rely on your sense of smell: hydrogen sulphide deadens the olfactory nerve above 100 ppm, so you may not detect lethal concentrations.

Set up emergency rescue arrangements

Regulation 5 requires suitable and sufficient rescue arrangements to be in place before any person enters a confined space. This is not optional and cannot be deferred until an emergency occurs. Your arrangements must provide:

• at least one person trained in confined space rescue who stays outside the space at all times during entry
• rescue equipment, including a rescue harness and lifeline, a mechanical lifting device (tripod and winch), self-contained breathing apparatus and resuscitation equipment
• a reliable way to raise the alarm and call for more help
• advance notice to the local fire and rescue service where high-risk entries are planned
• a trained first aider and first aid equipment on site
• a planned route to the nearest hospital with an accident and emergency department

The attendant (top person) must never enter the space to attempt a rescue. Untrained rescue attempts are one of the most common causes of multiple deaths in confined spaces. The attendant's role is to monitor the entrant's welfare, keep in contact and raise the alarm if something goes wrong.

Implement the permit to enter system

A permit to enter is a formal documented control that authorises entry into a specific confined space for a specific task within a defined time period. HSE’s Approved Code of Practice L101 requires a permit system for all but the most straightforward confined space entries.

The permit must specify:

• The confined space to be entered (location and identification)
• The work to be carried out
• The hazards identified in the risk assessment
• The precautions required (isolation, ventilation, monitoring, PPE)
• Time limits for the entry
• The names of authorised personnel (supervisor, entrants, attendant, rescue team)
• Emergency procedures and rescue arrangements

The permit must be issued by a competent person who has assessed the risks and verified that all precautions are in place. It is time-limited and must be cancelled and re-issued if conditions change — for example, if the weather changes, different work is needed, or there is a shift change.

Know when to report and what happens next

If something goes wrong during confined space work, you have legal reporting duties under RIDDOR 2013. Loss of consciousness caused by asphyxia in a confined space is a reportable specified injury under RIDDOR regulation 4, even if the person recovers fully. Report deaths, specified injuries and dangerous occurrences to HSE without delay, by telephone or online, and make sure the full report reaches HSE within 10 days. Report an injury that keeps a worker off normal duties for more than 7 days within 15 days. Keep a record of every reportable incident for 3 years.

Common mistakes to avoid

Going straight to planning an entry without first considering whether alternatives exist breaches Regulation 4(1), and HSE inspectors will ask for evidence of your assessment.

A single generic risk assessment for "confined space entry" does not meet the legal standard. Each entry must be assessed individually, accounting for the specific space, conditions and work.

Hydrogen sulphide deadens the sense of smell at higher concentrations, so by the time you cannot smell it the concentration may already be lethal. Always use calibrated instruments.

Planning to "call 999" is not a rescue arrangement. Rescue equipment and a trained person must be on site and ready before entry begins.

If the entrant becomes unresponsive, the natural reaction is to go in after them. This is exactly how confined space deaths become multiple deaths, so train your attendant to use the rescue equipment from outside.