Why it matters

Confined spaces kill quickly and often kill more than one person. A worker collapses from bad air, a colleague climbs in to help and collapses too. The air can look and smell normal and still kill you.

The WSH Council warns that a person can suffer permanent brain damage after roughly four minutes without enough oxygen. You have no time to improvise a rescue. Plan it and set up the kit before the first person goes in.

What counts as a confined space

Under Singapore law, a confined space is any chamber, tank, manhole, vat, silo, pit, pipe, flue or other enclosed space where at least one of these is true:

  • Dangerous gases, vapours or fumes may be present enough to cause fire, explosion or to overcome people.
  • The air supply is, or may become, inadequate to sustain life.
  • There is a risk of being engulfed by material, such as grain, sand or liquid.
Entry starts with the head

The regulations treat a person as having entered once their head passes through the opening. Leaning in to look or take a reading counts as entry.

The main hazards

Most deaths come from the atmosphere. Oxygen can be used up by rusting steel, rotting material or inert gas purging. Flammable gases and vapours collect from residues, leaks or solvents used during the work. Toxic gases such as hydrogen sulphide build up in sewers and pits.

Other hazards are physical. Grain or sludge can bury you. A mixer can start up. A pipeline can flood the space. Heat, poor light, wet floors and open manholes add to the risk. Welding or painting inside can also create bad air that was not there when you tested.

Order of controls

Work through these steps in order. Do not jump to breathing apparatus before you have tried the earlier ones.

  • Avoid entry. Ask whether the job can be done from outside with cameras, long tools, remote cleaning or by redesigning the task.
  • Isolate. Blank or disconnect pipelines, and lock out and tag out power, mixers and other energy sources. Check the isolation actually works.
  • Clean, purge and ventilate. Remove residues and run forced ventilation that reaches the work area, before and during entry.
  • Test and monitor. Test oxygen first, then flammables, then toxics, from outside. Keep at least one personal gas detector with the team inside.
  • Control the entry. Permit, barricade, warning signs, attendant, names displayed at the entrance, safe lighting and reliable communication.
  • Protect the person. Suitable respiratory protection, harness and lifeline where retrieval is possible, and other PPE for the task.

Gas testing and ventilation

The confined space safety assessor tests the air with a calibrated instrument, drawing samples from outside the space at different points and depths. Gases form layers. Heavy ones sink to the bottom and light ones rise to the top.

Ventilation must keep running while people are inside. WSH Council guidance says to retest when conditions might change, when work goes on for more than six hours, or when the space has been left unmonitored for 30 minutes or more. If an alarm sounds or a hazardous reading appears, everyone gets out at once and the permit is withdrawn.

What the rules require

The Workplace Safety and Health (Confined Spaces) Regulations 2009 set out the core duties. The WSH Council Technical Advisory explains how to meet them.

  • No entry or work without an evaluation and a confined space entry permit. The supervisor applies, the confined space safety assessor tests and endorses, and the authorised manager issues.
  • A hazardous atmosphere is one where oxygen is outside 19.5% to 23.5% by volume, flammable gas is at 10% or more of its lower explosive limit, or toxic substances exceed their permissible exposure levels.
  • The permit is posted at the entrance until it expires, is revoked, or the work is done. The authorised manager reviews it daily.
  • A confined space attendant is appointed to stay outside, monitor entrants and raise the alarm.
  • Entrants display their name or identification badge at the entrance, and warning signs are posted.
  • Workers and supervisors are trained, and a rescue operation is planned.
  • Portable hand lamps run at no more than 55 V AC or 110 V DC, and access routes are lit to at least 50 lux (Technical Advisory).
  • The Technical Advisory states that entry permits and test results must be kept for two years.
Legal requirement

The WSH Council lists SS 568: 2011 Code of Practice for Confined Spaces as an approved standard to follow alongside the Confined Spaces Regulations and the Risk Management Regulations.

Rescue planning

Write the rescue plan before work starts. Name the rescuers. Say how they will bring a casualty out, what kit they will use and how you will call them. Non-entry rescue, using a harness, lifeline and tripod winch, is safest where the space allows it.

Look at the opening and the layout inside. A small manhole or a tank full of baffles may block a rescuer wearing breathing apparatus. Run a drill on this space before you rely on the plan.

Do not go in after a casualty

Most multiple deaths start with an untrained worker going in to help. The attendant raises the alarm and starts non-entry rescue. Only trained rescuers with breathing apparatus go in.

Common mistakes

  • Testing only at the opening, or only at one depth.
  • Treating a space as safe because someone worked in it yesterday.
  • Switching off ventilation during breaks or when it gets noisy.
  • Starting hot work or painting inside a space without updating the permit.
  • Using a radio inside a steel tank and assuming it will work.
  • Letting the attendant take on other tasks or walk away.
  • Relying on calling emergency services as the whole rescue plan.
Smell is not a test

Hydrogen sulphide deadens the sense of smell, and low oxygen has no smell at all. Only a calibrated gas detector tells you the air is safe.

In other countries

  • Malaysia: DOSH's Industry Code of Practice for Safe Working in a Confined Space 2010 uses the same oxygen and 10% LEL limits. It requires workers in confined space operations to pass a training course approved by the Director General. A permit to work lasts no longer than the task or eight hours, whichever is shorter, and the entry supervisor can extend it once by up to four hours.
  • Indonesia: Permenaker No. 11 Tahun 2023 covers confined spaces, including wells and holes deeper than 1.5 metres. Employers classify spaces as permit or non-permit. Nobody enters a permit space without an entry permit, issued after an Ahli K3 checks gas testing, continuous ventilation, energy lockout, communication and rescue arrangements. Power supplies inside must not exceed 50 V in dry conditions or 25 V in damp conditions.

Use it on site: the confined spaces checklist and the toolbox talk to brief your crew.

Sources

  1. Workplace Safety and Health (Confined Spaces) Regulations 2009, Singapore Statutes Online.
  2. Technical Advisory on Working Safely in Confined Spaces, WSH Council.
  3. About Confined Spaces, WSH Council.
  4. Industry Code of Practice for Safe Working in a Confined Space 2010, DOSH Malaysia.
  5. Permenaker No. 11 Tahun 2023 tentang K3 di Ruang Terbatas, BPK RI (JDIH).

This is practical guidance, not legal advice. Laws and codes of practice change; always check the current official text and your site's own procedures.