In brief
Confined spaces are volumes such as tanks, silos, wells, ducts and reactors that are not designed for working in, have restricted entry and exit and whose atmosphere can quickly become dangerous. The fatal risks here are mostly invisible: oxygen deficiency, toxic and flammable gases. Before entry, energy and line isolation, gas testing, ventilation, a written entry permit, an attendant waiting outside and a ready rescue plan are required.
What is a confined space, and when does confined space work begin?
A confined space is a volume that is not designed as a place of continuous work, has restricted entry and exit, and in which the atmosphere or material inside can quickly become dangerous for an employee. You can test whether a volume falls within this definition with three questions:
- Was this volume designed for working inside, or for storing, moving or processing a substance?
- Is entry and exit through a manhole, a narrow hatch, a vertical ladder or an opening you crawl through?
- Can the atmosphere inside become deficient in oxygen, build up toxic or flammable gas, or can the material inside engulf the employee?
If the answer to all three questions is "yes", entering that volume is not an ordinary maintenance task but work in a confined space, and it must be managed with separate rules.
| Confined space | Businesses where it is common | Typical reason for entry |
|---|---|---|
| Chemical and solvent tank | Chemicals, paint, coating | Cleaning, repair of internal lining, inspection |
| Reactor and mixer vessel | Chemicals, resin, adhesive | Residue cleaning, agitator maintenance |
| Granule and powder silo | Plastic injection moulding and extrusion | Clearing bridged material, sensor repair |
| Waste water pit, manhole, well | Almost every facility | Pump maintenance, clearing blockages |
| Duct, tunnel, large-diameter pipe | Infrastructure, energy, ventilation | Cable pulling, cleaning, inspection |
| Inside an oven, drying tunnel, boiler | Metal, textiles, food | Refractory repair, internal inspection |
The legal basis for confined space work is the general provisions of Law No. 6331 on Occupational Health and Safety. The employer is obliged to take the necessary measures to ensure that employees other than those given adequate information and instructions do not enter places with vital and special hazards (Art. 4/1-d). Each confined space should be dealt with as a separate row in the risk assessment (Art. 10), and entries should be tied to a written permit system.
Confined space risks: the invisible atmosphere
The deadliest confined space risks have one thing in common: they cannot be noticed by sight and often not by smell. In normal air, the proportion of oxygen is about 20.9 per cent. In international practice, for example in the confined space standard of the US occupational safety administration OSHA, below 19.5 per cent by volume is considered oxygen-deficient, and above 23.5 per cent an oxygen-enriched atmosphere that accelerates combustion. For flammable gases, 10 per cent of the lower explosive limit (LEL) is the common threshold at which entry is stopped.
| Atmospheric hazard | Where does it come from? | Why is it not noticed? |
|---|---|---|
| Oxygen deficiency | Tank purged with nitrogen (inerted), rusting steel surface, fermenting organic matter | Nitrogen has no colour or smell; the first sign may be loss of consciousness |
| Hydrogen sulphide (H₂S) | Waste water, sludge, rotting organic matter | At high concentrations it deadens the sense of smell; people think the smell has "gone" |
| Carbon monoxide (CO) | An engine or generator running inside or at the entrance, combustion processes | Colourless and odourless |
| Solvent vapour | Solvent, paint and resin residue left at the bottom of the tank | Vapours heavier than air collect at the bottom; a reading at the manhole may come out clean |
| Flammable atmosphere | Solvent vapour, methane, fine dust | A single spark (welding, grinding, an unsuitable lamp) is enough |
The safety data sheet shows what the residue in the tank is and which gas it produces; the entry plan should be prepared with this information.
Risks other than the atmosphere
Even without gas, a confined space carries other hazards:
- Engulfment: Free-flowing solids such as plastic granules, powder and grain can bury an employee very quickly when a bridged surface collapses.
- Mechanical energy: If an agitator, screw conveyor, pump or feed valve is started by mistake, the person inside is put in direct danger.
- Substances from connected lines: Steam, hot water, chemicals or nitrogen coming from a pipeline.
- Temperature: A newly emptied reactor or a tank in the sun causes heat stress.
- Falls and entrapment: Steep ladders, slippery internal surfaces, narrow manholes.
- Difficulty of rescue: Getting an unconscious person out through a narrow manhole is very difficult if it has not been planned in advance.
Confined space entry permit: the basic conditions
Confined space entry is the most strictly applied part of the general permit-to-work system. A confined space entry permit is not just a form to be filled in; it is a signed record showing that each of the following conditions has been verified on site:
- Description of the space and the work: Which tank, which job, how many people, how long.
- Energy isolation: Agitators, pumps, screw conveyors and heaters are locked and tagged; zero energy is verified by testing.
- Line isolation: Lines connected to the tank are separated with blank flanges or removed; simply closing a valve is not considered enough.
- Emptying and cleaning: The contents are emptied; if possible, washing or steam cleaning is first done from outside.
- Ventilation: If natural ventilation is not enough, mechanical ventilation is installed. Ventilation is never done with pure oxygen.
- Gas testing: Oxygen, flammable gas and expected toxic gases are measured just before entry; the results, the tester and the device are written on the permit. Testing is repeated while work continues, or a personal detector is carried inside.
- PPE and equipment: Full body harness and rescue line, breathing apparatus if necessary, lighting suitable for the atmosphere and non-sparking hand tools.
- Attendant and communication: At least one attendant outside and uninterrupted communication with those inside.
- Rescue plan: Rescue equipment such as a tripod and winch ready at the entrance, with the rescue team and the order of calling 112 clearly defined.
- Duration and close-out: The permit is closed at the end of the shift or job; the space is handed back after verifying that no people or tools remain inside.
If welding or cutting is to be done in the space, a hot work permit is also issued in addition to the entry permit.
What does a confined space attendant do, and not do?
The confined space attendant is the person who stays outside the space and is responsible for the safety of the employees inside. Their job is not to do the work but to watch.
The attendant:
- Knows how many people are inside and who they are, and records entries and exits.
- Stays in constant communication with those inside by sight, voice or radio.
- Calls the employees out immediately when the detector alarms, when there is no response from inside or when a new hazard starts nearby (for example, welding work next to the space).
- Prevents unauthorised people from entering.
- In an emergency, raises the alarm, calls the rescue team and 112, and starts the response from outside with the rescue line.
The attendant does not:
- Leave their post or help with another job.
- Go inside without the rescue equipment defined in the plan and a back-up attendant to take their place.
The attendant should be someone who knows the job and is trained for this role. Especially with subcontractor teams, make sure the entry team and the attendant speak the same language and know the same signals.
Common scenarios in chemical and plastics plants
In chemicals and plastics businesses operating in Bursa's OIZs (organised industrial zones), confined space entries often arise as part of routine maintenance; the risk arises precisely from this routine.
- Reactor or mixer cleaning: Residual solvent vapour, the agitator being started by mistake and a narrow manhole all come together. First wash from outside, then enter with energy lockout and testing.
- Solvent tank inspection: Even if the tank looks empty, the sludge at the bottom keeps producing vapour. Ventilation should run throughout the work and testing should be repeated.
- Clearing a bridge in a granule silo: Rather than entering the silo from above, intervention from outside with vibrators, air blasters or long-handled tools should be preferred. If entry is unavoidable, feeding and discharge are locked out and the employee is attached to a rescue line.
- Equipment inerted with nitrogen: A tank purged with nitrogen against explosion risk is oxygen-free for the same reason. No entry should be made before the nitrogen line is separated and oxygen is measured.
Areas where a flammable atmosphere can form should also be defined in the explosion protection document; for the general management of the chemicals used, see our article on the chemical agents regulation.
Risk assessment, training and the emergency plan
Confined space safety comes together in three documents:
- Risk assessment: Draw up an inventory of all confined spaces in the facility: location, contents, entry point, connected lines and energy sources. For each one, first ask "can this job be done without going inside?"; the most effective measure is not to go inside at all. In our risk assessment service, we draw up this inventory on site together with your maintenance team.
- Training: The entrant, the attendant and the person issuing the permit are trained for their own roles. The job- and workplace-specific risks part of basic OHS training is given face to face in hazardous and very hazardous workplaces; confined space practices are a natural topic for this part.
- Emergency plan: A scenario of collapse or injury in a confined space should be written into the plan together with rescue equipment and team duties, and should be drilled.
We deal with confined space entries under our OHS specialist service, together with the procedure, permit form and checks of on-site practice.
Frequently Asked Questions
What is a confined space, and is every cramped space a confined space?
No. A confined space is a volume not designed for working in, with restricted entry and exit, whose atmosphere or contents can become dangerous for an employee. A small storeroom with adequate ventilation that you can easily enter and leave through its door does not fall within this definition.
If the gas test is clean, is a permit still needed?
Yes. Testing is only one of the conditions of the permit. Without energy and line isolation, ventilation, an attendant and a rescue plan, a clean test result does not mean safe entry; the atmosphere can also change during work.
Can the confined space attendant go inside?
Not without the rescue equipment defined in the plan and a back-up attendant to take their place. The attendant's main job is to watch the inside, raise the alarm and start the rescue from outside.
Which legislation applies to confined space work?
The general framework is Law No. 6331: restricting entry to places with vital hazards (Art. 4/1-d), risk assessment (Art. 10), emergencies (Art. 11) and training (Art. 17). Depending on the contents of the space, the regulations on chemical agents, explosive atmospheres and work equipment also apply.
A certified specialist matched to your hazard class: site inspections, approved logbook, training plan, annual plan and report follow-up.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.