Confined spaces cause serious injuries and deaths, and often more than one person is harmed in the same incident because a would-be rescuer enters after a co-worker. This guide describes in general terms how permit-based entry systems work. It does not replace the rules of your jurisdiction, your employer’s procedures or training by a qualified provider. Nobody should enter a confined space based on a general article.
What counts as a confined space
Definitions vary by country, but the typical features are:
- The space is large enough for a person to enter and do work.
- It has limited or restricted ways in and out.
- It is not designed for continuous occupancy.
Examples include tanks, silos, hoppers, vessels, boilers, pits, vaults, sewers, ducts and some trenches. A space is not automatically dangerous because it is small. What matters is what hazards it contains or could develop.
Permit-required and other spaces
Many regulations divide confined spaces into categories. In a common approach, a space becomes permit-required if it has certain serious hazards, such as:
- A hazardous atmosphere, which may be too low in oxygen, too high in oxygen, flammable, or contaminated with toxic gases or dust.
- A material that could engulf an entrant, such as grain or liquid.
- Walls that slope or taper inward, or floors that slope downward to a smaller section, so that a person could be trapped or asphyxiated.
- Any other recognized serious safety or health hazard, such as unguarded moving parts or live electrical equipment.
Spaces without such hazards may be subject to lighter requirements, and some jurisdictions allow reclassification when hazards are eliminated or fully controlled by approved methods. Terminology and conditions differ, so check how your regulator defines each category.
An employer typically must identify and evaluate its spaces, mark or inform workers about permit-required ones, and decide whether employees will enter at all. Some employers prohibit entry by their own staff and use specialized contractors.
What an entry permit does
A permit is a written authorization completed before each entry. It acts as a checklist and a record. Although format differs, a permit commonly records:
- Which space and what work is planned.
- The date, time and duration of the entry.
- Hazards identified and the controls in place.
- Atmospheric test results.
- How energy sources and material flows have been isolated.
- Ventilation or purging arrangements.
- Names of entrants, attendant and entry supervisor.
- Communication method and emergency or rescue arrangements.
- Equipment required, such as protective gear, lighting and retrieval systems.
- Authorization signature, and a cancellation step when work ends.
The point is not paperwork for its own sake. Completing it forces people to think about hazards and confirm that preparations are done before the first person goes in.
Preparing the space
Before entry, hazards are generally reduced as far as possible. Preparation often includes:
- Isolating energy and flows. Machinery inside the space is locked out under lockout tagout procedures, and pipes that could feed in liquids, gases or steam are blanked, disconnected or otherwise positively isolated according to site procedures.
- Emptying and cleaning. Contents are removed and residues cleaned, sometimes by specialist crews.
- Ventilating. Fresh air is supplied mechanically where needed to keep the atmosphere acceptable.
- Controlling other hazards. Heat, noise, slippery surfaces, falling objects and electrical hazards are reviewed.
Atmospheric testing
Testing the air is one of the most important duties because many fatal incidents involve atmospheres that cannot be detected by sight or smell. In general terms:
- Testing is done with a calibrated, properly maintained instrument by a trained person, following the instrument’s manual.
- Testing is typically done before entry, from outside where possible, and the sequence usually checks oxygen first, then flammable gases or vapors, then specific toxic gases that could be present.
- The space is often tested at different levels, since gases lighter or heavier than air collect in different places.
- Results are recorded, and acceptable limits come from local regulations and the permit.
- Monitoring continues during the work in many systems, either by continuous monitors or periodic retesting, because conditions can change, especially when work such as welding, cleaning or solvent use introduces new contaminants.
A reading outside acceptable limits means entrants leave and the situation is reassessed. Instruments are bump-tested or calibrated according to the manufacturer’s instructions and company policy. The choice of detection and retrieval equipment is covered in separate articles on confined space gear and entry retrieval systems.
Roles
Systems usually define three main roles:
- Authorized entrants go into the space. They are trained in the hazards, signs and symptoms of exposure, equipment use and when to leave. They are expected to exit when told to, when they notice a hazard warning sign, or when an alarm sounds.
- Attendants stay outside for the whole time people are inside. They keep an accurate count of who is in the space, maintain communication, watch for changes in conditions, and call for rescue when needed. A key rule in most frameworks is that the attendant does not enter to attempt a rescue and does not take on duties that distract from watching entrants.
- Entry supervisors are responsible for checking that conditions on the permit are met, authorizing entry, verifying that rescue services are available, and canceling the permit when work ends or conditions change.
One person may hold more than one role in some systems, provided they are trained and the duties do not conflict, but the attendant role generally cannot be combined with entering.
Rescue planning
Rescue arrangements must be settled before anyone enters. Options typically include trained on-site rescue teams, outside emergency services that have confirmed they can respond in time and have appropriate equipment, or non-entry retrieval using harnesses and lines where the space layout allows. Responders who have not practiced in a similar space may not be able to help effectively, so many programs include drills.
Training and review
Everyone involved should be trained for their role before they are assigned, and again when duties, hazards or procedures change. Employers commonly review the permit system periodically, using canceled permits to spot problems. Requirements for retention of permits and training records depend on the jurisdiction.
Confined space work is a case where general guidance should always yield to the site’s written program, the relevant regulations and trained professionals.