The Hidden Danger
Confined space incidents often result in multiple fatalities—because when one person collapses, others enter to rescue them without proper precautions and suffer the same fate. In the UK, around 15 people die in confined spaces each year, and many more are seriously injured.
The Confined Spaces Regulations 1997 place strict duties on employers to protect workers. This guide explains how to identify confined spaces, assess the risks, and implement safe systems of work.
What is a Confined Space?
A confined space is any place that is substantially enclosed (though not always entirely) and where serious injury can occur from hazardous substances or conditions within the space or nearby.
Common Confined Spaces in Construction
- Manholes and sewers
- Inspection chambers and pits
- Tanks and vessels
- Silos and hoppers
- Excavations and trenches
- Tunnels and shafts
- Ductwork and flues
- Ceiling voids
- Unventilated rooms
- Ship holds and containers
What Makes a Space Dangerous?
Confined spaces may contain:
- Oxygen deficiency: Displacement by other gases, consumption by rusting, biological activity
- Oxygen enrichment: Leaking oxygen lines, increasing fire risk
- Toxic gases: Hydrogen sulphide, carbon monoxide, chlorine
- Flammable gases: Methane, petrol vapour, solvents
- Free-flowing solids: Grain, sand, that can engulf
- Liquids: Flooding risk
- Excessive heat: Leading to heat stress
The Hierarchy of Controls
The Confined Spaces Regulations require you to:
- Avoid entry if possible—do the work from outside
- If entry is unavoidable, follow a safe system of work
- Have emergency arrangements in place
Can Entry Be Avoided?
Before planning confined space entry, ask whether the work can be done another way:
- Remote cameras for inspection
- Long-handled tools for cleaning or sampling
- Automation of processes
- Modification of the work to eliminate entry need
Risk Assessment for Confined Spaces
If entry is necessary, conduct a thorough risk assessment:
Task and Space Assessment
- What work will be done inside?
- How long will workers be inside?
- What is the size and configuration of the space?
- What are entry and exit points?
- What equipment must be taken in?
Atmospheric Hazards
- What was previously stored or processed?
- What residues might remain?
- Are there connected pipes or vessels?
- Is natural ventilation adequate?
- What gases might accumulate?
- Is there oxygen depletion or enrichment risk?
Physical Hazards
- Engulfment from free-flowing materials
- Flooding from liquids
- Moving machinery
- Electrical hazards
- Temperature extremes
- Poor lighting
- Difficult access/egress
Safe System of Work Elements
1. Competent Supervision
- Supervisor trained in confined space work
- Authority to stop work if conditions change
- Present throughout or immediately available
2. Competent Workers
- Training in confined space hazards and controls
- Training in emergency procedures
- Understanding of atmospheric monitoring equipment
- Medical fitness for the work
3. Isolation
- Mechanical isolation of connected plant
- Electrical isolation (lock-out/tag-out)
- Blanking or disconnection of pipes
- Prevention of ingress of hazardous materials
4. Atmospheric Testing and Monitoring
- Test before entry for oxygen, flammable gases, toxic gases
- Use correctly calibrated equipment
- Test at different levels (gases stratify)
- Continuous monitoring during work
- Personal gas detectors for all entrants
5. Ventilation
- Mechanical ventilation to ensure safe atmosphere
- Correctly positioned to ensure air reaches all areas
- Sufficient capacity for the space size
- Clean air source—not from contaminated area
6. Permit to Work
A formal written permit should cover:
- Description of work and space
- Hazards identified
- Precautions required
- Atmospheric test results
- Emergency procedures
- Time limits
- Authorisation signatures
7. Personal Protective Equipment
- Breathing apparatus where atmosphere cannot be assured
- Safety harness with retrieval line where practical
- Protective clothing appropriate to hazards
- Communication equipment
- Lighting (intrinsically safe if flammable atmosphere possible)
8. Access and Egress
- Safe means of entry and exit
- Ladders secured and appropriate
- Adequate space for emergency retrieval
- Entry point monitored at all times
Emergency and Rescue Arrangements
You must have emergency arrangements before any entry. Never assume you can improvise.
Key Requirements
- Rescue plan specific to the space
- Rescue equipment immediately available
- Trained rescue personnel on site or on call
- Raising the alarm procedure
- Emergency services pre-notified if appropriate
- First aid equipment and trained personnel
Rescue Considerations
- Never enter to rescue without protection—more casualties result from unprotected rescue attempts
- Retrieval from outside is safest—use harness and retrieval system
- Self-contained breathing apparatus for rescuers if atmosphere hazardous
- Practice rescue drills for the specific space
Top-Man Requirements
The "top man" or attendant must:
- Remain at the entry point at all times
- Maintain communication with those inside
- Monitor for changes in conditions
- Summon help if emergency arises
- Never enter the space to attempt rescue
- Be trained in emergency procedures
Atmospheric Testing Guidelines
Safe Levels
| Parameter | Safe Range |
|---|---|
| Oxygen | 19.5% - 23.5% |
| Flammable gases | Less than 10% LEL |
| Carbon monoxide | Less than 30 ppm |
| Hydrogen sulphide | Less than 5 ppm |
Testing Procedure
- Calibrate equipment before use
- Test from outside before entry
- Test at multiple levels (top, middle, bottom)
- Allow sufficient time for readings to stabilise
- Record all results
- Continue monitoring throughout work
Documentation Checklist
- Confined space risk assessment
- Safe system of work/method statement
- Permit to work
- Atmospheric test records
- Equipment inspection records
- Training records for all personnel
- Emergency plan
- Rescue drill records
Conclusion
Confined space work requires rigorous planning and strict procedural control. The consequences of getting it wrong are severe—but with proper risk assessment and safe systems of work, confined space entry can be managed safely.
When generating RAMS for work involving confined spaces, ensure you address all the elements covered in this guide. DocGen can help identify confined space scenarios, but specialist input is essential for developing safe systems of work.