Work at height permit
what it must prove before anyone leaves the ground

Scaffolding, elevating work platforms, roof work, structural steel, rope access, a ladder at a flange. In a permit to work system, height is a permit condition rather than a trade: the paperwork exists because the fall is over in a second and everything that decides the outcome — the access, the anchor, the exclusion zone below, the rescue — is chosen before it.

What counts as work at height?

Not the ladder, not the scaffold, not the job title — the possibility of falling. Every serious permit to work system uses the same test: could a person fall from this position, and would the fall injure them. If the answer is yes and the structure does not already prevent it with a guardrail, the job needs authorising.

Two of these are consistently underestimated. A ladder feels like equipment rather than work at height, and it produces some of the most severe injuries because the fall is short, unbroken and onto machinery. And work below an opening qualifies too: the man on the floor is in the exclusion zone of the man above, and the permit covers both.

What must the permit control?

A work at height permit has to control four things across the life of the job: the access, the anchor, the exclusion zone and the rescue plan. It proves each of them before signature, keeps them real while people are exposed, and closes them out deliberately rather than letting them lapse when the crew walks away.

Before the signature.

1. Establish the access and prove it has been inspected — a scaffold tag current for this shift, a pre-use check on the platform, an inspection record for harnesses and lanyards.
2. Identify the anchor points and confirm they are rated and independent of what is supporting the work.
3. Define the exclusion zone below, on the ground and on any level the work overhangs.
4. Agree what else will be happening around and beneath the job, because the risk that kills is rarely the one the permit was raised for.
5. Confirm the weather limits that apply to the equipment, particularly wind on platforms and lifting.

During the work.

1. Keep the exclusion zone real — barriers, signs and someone with the authority to stop people walking under the job.
2. Tether tools and secure materials; a dropped spanner is a lethal weapon from twenty metres, and the practice for tethering is set out in ANSI/ISEA 121.
3. Stop when the access changes — a scaffold altered by another trade is a new structure and needs re-inspection before it is used again.
4. Stop for weather at the equipment’s stated limit, not at the point where it feels bad.

After the work.

1. Recover the equipment and hand back the access, or formally leave it tagged for the next crew with the reason.
2. Remove or re-secure any edge protection that was taken down.
3. Close the permit so the exclusion zone is lifted deliberately rather than dissolving when the crew walks away.
4. Log any harness or lanyard that arrested a fall — those are withdrawn from service, not reused.

The threshold: why the number is different everywhere

This is the first question every contractor asks on a new site, and the honest answer is that the number belongs to the jurisdiction and to the client’s own standard, whichever is stricter.

The regulation is a floor, not a target. Where an international contractor works to two systems at once — its own and the client’s — the rule that survives an audit is to apply the stricter one and record which one was applied.

Access: chosen, then proved

The order in every mature system is the same, and it is a hierarchy of preference, not a menu:

1. Avoid the work at height, if the job can be done from the ground.
2. Prevent the fall with a structure, if avoidance is not possible.
3. Arrest the fall with a system, only when prevention is impossible.

• Scaffolding. Inspected by a competent person before each shift under OSHA 1926.451(f)(3), and after any alteration or severe weather. The tag carries the date and the inspector; an untagged or expired scaffold is not access, it is a structure standing there.
• Mobile elevating work platforms. Pre-use check, ground conditions confirmed, the machine’s own wind limit respected, and the entrapment risk considered — crushing against steelwork above is a documented killer on boom platforms. Training and safe use are covered by the ANSI A92 family and ISO 18893.
• Ladders. Not banned anywhere, but a last resort for short-duration light work where three points of contact remain possible. If the job needs two hands and force, the ladder is the wrong access.
• Rope access. A discipline in its own right, with its own competence scheme, two independent systems and a supervisor at the top. It is not a harness plus improvisation.

The anchor and the arrest chain

A fall arrest system is a chain: anchor, connector, lanyard or inertia block, harness, and the space below to stop in. It has the strength of its weakest element, and the element most often chosen by eye is the anchor.

• Rating. OSHA 1926.502(d)(15) sets 22.2 kN (5,000 lb) per attached worker, or design by a qualified person with a safety factor of at least two. Handrails, cable trays, small-bore pipework and scaffold couplers are not anchors.
• Independence. The anchor must not depend on whatever holds the platform up. If the scaffold collapses, the anchor tied to it goes with the person.
• Arrest force and free fall. The system must limit the force on the body to 8 kN (1,800 lb) with a full body harness, keep free fall to 1.8 m (6 ft) or less, and limit deceleration distance to 1.07 m (3.5 ft) — OSHA 1926.502(d)(16).
• Clearance below. The arithmetic no one does on the day: lanyard length, plus shock absorber extension, plus the height of the worker below the anchor, plus a safety margin. If the total is more than the distance to the level below, the system stops the fall after the impact.

Rescue: the part most permits leave blank

A fall arrest system works when it leaves someone hanging alive in a harness. That is where the permit either has an answer or does not.

No standard offers a safe hanging time; the recognised guidance is that harness suspension is a medical emergency and that recovery must be prompt, which is why ANSI/ASSP Z359.2 requires rescue to be part of a managed fall protection programme rather than a reaction. On a live plant that means a named team, equipment already at the workface, and a route — not a phone call to a service that has to find the gate, cross the site and get elevated equipment to the position.

Three questions decide whether the plan is real: who performs the recovery, with what, and how long it takes them to reach the person. If the answer to any of them is “the emergency services”, the plan is a hope. Rescue from a platform is usually a matter of driving the basket down; rescue from steelwork or a rope is a rehearsed operation, and the permit is where the difference is recorded.

How is the requirement written in different countries?

The engineering behind a work at height permit is close to identical everywhere; what differs is the instrument that makes it mandatory and the numbers it sets. The United States writes prescriptive figures for anchors, arrest forces and free fall directly into regulation; China sets a national height threshold and, in hazardous plants, requires the permit itself; the United Kingdom sets no threshold at all and relies on a legal hierarchy instead.

Where work at height permits fail

Not on the form. In the same five places:

• the anchor is chosen on the day, by eye, from whatever is within reach;
• the exclusion zone exists on paper and is walked through by everyone, because nobody was given authority to stop them;
• the scaffold is altered by another trade and used again without re-inspection;
• the clearance below is never calculated, so the arrest system works exactly as designed and the person still reaches the floor;
• rescue is left as “call for help”, which converts a survivable fall into a fatality while everyone watches.

Every one of these is visible in the permit afterwards, which is the point: the record is the only evidence that the choice was made before the job rather than during it. On paper that evidence survives as long as the folder does; held as data it can also be counted across jobs, and rescue is the field that turns up blank first when anyone counts.

Standards cited

• 29 CFR 1926.502 — OSHA, United States · Fall protection systems criteria and practices · Criteria for fall protection systems on construction sites · In force
• NOM-009-STPS-2011 — STPS, Mexico · Condiciones de seguridad para realizar trabajos en altura · Safety conditions for work at height · In force
• GB 30871-2022 — SAMR / SAC, China · 危险化学品企业特殊作业安全规范 · Eight special operations in hazardous chemical enterprises; a permit is mandatory for each · In force

Frequently asked questions