Restricted zones and work at height: AI video safety monitoring

What restricted zones and work at height cover

Restricted zones and work at height are two parts of workplace safety that come down to the same question: should this person be here, doing this, protected this way? A restricted zone is an area where entry is limited to people doing planned, authorized work — because of moving machinery, live electrical equipment, suspended loads, hazardous substances or the air itself. Work at height is any work where a person could be injured by falling to a lower level. In both, the danger is not the place alone but who is in it and how. The topic shows up in seven situations.

Danger zones: robot cells, high-voltage rooms, lifting zones, chemical areas

Each of these areas is fenced, locked or signed for a reason. A robot arm moves fast and without warning; a high-voltage room holds live equipment; under a crane, the load can drop; in a chemical store or process area, a leak or a vapor can do harm before anyone notices. People enter for legitimate reasons — maintenance, cleaning, inspection — and for other ones: a shortcut, a dropped tool, a task nobody planned.

Permitted maintenance versus unauthorized entry

The same door opens for both. A technician with a work permit, the right equipment and the hazard made safe is doing planned work; a colleague who follows them in to fetch a part is not. A zone-entry rule sees two people crossing the same line. The difference lies in what each person is doing, what they carry and wear, and what is happening around them.

Work at height without a harness or anchor

Where collective protection — guardrails, platforms, nets — can't remove the fall risk, the person working at height relies on a full-body harness attached to an anchor point or a lifeline. A harness left in the van protects no one, and neither does one that is worn but not attached. The shortcut is tempting on short jobs: changing a lamp, freeing a jammed pallet on high racking, a quick look at a roof unit.

Ladders and platforms

Ladders, mobile platforms and scaffolds put people at height for a few minutes at a time, in the middle of a working floor. Overreaching from a ladder, standing on the top step, climbing racking instead of fetching a platform, or removing a platform's guardrail to reach the work are everyday versions of the same risk.

Roof and mezzanine edges

Roofs, mezzanine floors and raised loading platforms have edges that are easy to forget while concentrating on the job. Fragile roof sheets and skylights add a hidden edge in the middle of a roof. A guardrail section removed to lift goods onto a mezzanine leaves an open edge for everyone who comes after.

Confined spaces: entry without a permit or attendant

Tanks, silos, pits, vessels, sewers and large ducts are confined spaces: hard to get into and out of, with air that can be short of oxygen or hold toxic or flammable gases. Safe entry is planned: a permit, atmosphere testing, ventilation, rescue arrangements, and someone outside who keeps watch and can raise the alarm. Without them, a confined space can harm the worker inside — and then the colleague who goes in to help.

Contractors and non-routine work

When outside crews come in for roof repairs, tank cleaning, electrical upgrades or crane lifts, they work on a site they don't know. They may not know which doors lead into a restricted zone, where the anchor points are, or which rules apply to this roof. Non-routine work also leaves less time to plan, and the permit is written under time pressure.

Why traditional methods miss restricted-zone and height violations

Safety rules are clear about what has to be in place. People with no task there must be kept, by suitable means, out of dangerous areas where materials or workers can fall; the people authorized to enter must be protected; and these areas must be clearly marked. The open sides of raised walkways, platforms and working landings need suitable guardrails wherever workers are at risk of falling. Work at height means any work where a difference in level could cause injury from a fall: collective protection such as guardrails and platforms comes first, and where that is not enough, full-body harnesses or similar fall-arrest systems are used with anchor points or lifelines. Work in spaces with a limited volume of air is allowed only where it is unavoidable and every measure has been taken, and then the workers inside must be continuously monitored from outside.

The rules are written down. What is hard is seeing, on every shift, whether they hold.

• Permits live on paper. A permit to work says who may enter, when and under which precautions. It does not show whether anyone else walked in, or whether the precautions were still in place an hour later. Checking that means being there.
• Signs and barriers are ignored. A sign or a chain across a doorway marks the zone; it doesn't stop a person in a hurry. A barrier moved for a delivery may not be put back.
• Zone-trigger cameras can't tell permitted work from unauthorized entry. A rule that fires whenever a person crosses into a zone fires for the electrician on a permit and for the person taking a shortcut alike. Sites that keep it on get a stream of alarms for planned maintenance; sites that switch it off during maintenance windows lose sight of the zone exactly when its door is open.
• Periodic audits see a moment, not the site. A safety walk sees the roof on the day of the walk, and people behave differently when they know they are being watched. The harness-free job on the far side of the roof the next morning is not on the route.
• Manual CCTV review doesn't scale. The cameras may already cover the doors and the roof. But checking them means knowing which camera and which minute to watch, so footage is reviewed after an incident — not to find the entries and edges that came before it.

What these methods lack is the judgment a safety professional makes at the doorway or the roof edge: is this person part of the planned work, and are they protected for it?

How vision-language models make it solvable

Primarch builds on and enhances vision-language models (VLMs): models that read video and language together. Instead of checking whether a box labeled "person" sits inside a zone drawn on the screen, the model reads the scene the way an experienced safety professional would — on every camera, on every shift.

• It reads what a person is doing in the zone, not just that they are there. Tools in hand and work on the equipment, the protective equipment the task calls for — or a person walking straight through, looking for something, reaching past a barrier. Reading these cues together is designed to tell unauthorized entry apart from permitted maintenance.
• It reads time windows, not single frames. The before and after of an action are read together: a person stepping over a chain and walking on, or a technician who arrives with a toolbag and starts work on a panel.
• It reads work at height at the level of the action. Not a person detected above a line on the screen, but a person working on a roof edge, a mezzanine, a platform or high racking — and whether they wear a harness. That is how harness-free work at height can be caught when it happens, rather than found in an incident report.
• It uses context instead of fixed rules. Context — planned work versus a shortcut, a visitor versus a technician — is what separates normal work from risk. Reading the scene in context is designed to remove the biggest source of false alarms in rule-based systems: rules firing without context.
• It writes the finding in plain language, with a clip. The result is a sentence a supervisor can read — what happened, where, and why it matters — with a time-stamped evidence clip, so everyone discussing it sees the same thing.
• It chains events by shift, zone and time. Single events are recorded and alerted for review; chained together, they show where and when the same situation repeats, and help diagnose why: an attention lapse, or a process gap.

The useful question is not "did a person cross into the zone?" It is "is this person doing the planned work, equipped for it — or passing through?" At height, it is not "is someone up there?" but "is someone working at the edge without a harness?"

Coverage depends on the cameras. A doorway can be read only where a camera sees it; a roof, only where a camera covers the roof and its edges. Video reads what is visible: it does not measure the air inside a tank, and it does not replace the permit, the gas test or the rescue plan. Work inside machines — guards, interlocks and lockout — is covered in our guide to LOTO and machine guarding; lift trucks and people on foot in forklift and pedestrian safety.

What to look for in a solution

Whichever vendor you talk to, these are fair questions to ask about a system meant to monitor restricted zones and work at height with video:

• Works on your existing cameras. Can it connect to the IP cameras you already have, or does every door and roof need new hardware?
• Tells permitted work from unauthorized entry. Ask how it separates a technician doing planned maintenance from a person who should not be in the zone — and what it does during maintenance windows, when the door stays open.
• Reads work at height as an action. Does it recognize a person working at an edge or on a platform without a harness, or does it only detect people above a line on the screen?
• Is clear about what video can and can't verify. Permits, gas tests, anchor points and the person keeping watch outside a confined space: ask which of these a camera can actually show at your site.
• Handles false alarms openly. Ask how findings are reviewed by a person, and how single events are separated from repeating patterns.
• Explains repeats. Can events be grouped by shift, zone and time, and does it help separate an attention lapse from a process or layout gap?
• Produces reports your safety team can use. Findings written in regulatory language, corrective actions with owners, and zone-level summaries for the safety committee and audits.
• Respects privacy. Is footage anonymized? Is there an on-premise option where footage never leaves the site, and can it run on an isolated network if your site requires one? Does it meet GDPR and other data-protection requirements, and does it report situations rather than individuals?
• Can be piloted on your own site. One zone, a few of your cameras, your own work — not a demo video.
• Gets alerts to the right role. An instant alert for the shift supervisor, a digest for the safety team, a dashboard for site management.

Example use cases

The walk-throughs below are illustrative examples of how a finding is built. They are not customer cases and contain no performance figures.

Example 1: a shortcut through the electrical room during maintenance

1. 01

   Moment

   A food plant's main electrical room, 14:10. A camera covers the inside of the door and the switchgear aisle.

2. 02

   What the camera shows

   At 13:30 a person with a toolbag enters and starts work on a panel; this is planned maintenance and raises no alert. At 14:10, with the door propped open for the job, a second person walks in, crosses the room to the far door that leads to the packing hall, and walks out.

3. 03

   The finding + evidence clip

   "Unauthorized entry into the main electrical room: a person walked through the switchgear aisle to the packing hall while the door was open for maintenance; no work activity." The clip covers the seconds before and after.

4. 04

   Who is alerted

   The maintenance supervisor receives an instant notification; the event goes into the safety team's weekly digest.

5. 05

   What the shift and zone pattern shows

   Similar entries fall inside maintenance windows, when the door is left open, and each uses the room as a route to the packing hall.

6. 06

   Corrective action

   Diagnosis: a process gap — while the door stands open for maintenance, the room is the shortest route to the packing hall. Recommendation for the maintenance manager: keep the door closed or barriered while work is under way, and mark a walking route to the packing hall around the room.

Example 2: tools passed down at a roof edge without a harness

1. 01

   Moment

   The roof of a distribution center, 08:40, during repair work on rooftop units. A camera covers the roof area around the units and the nearby edge.

2. 02

   What the camera shows

   Two workers in harnesses work at the units. A third walks to the roof edge to lower tools to the ground and works there for several minutes, a step from the open edge, without a harness.

3. 03

   The finding + evidence clip

   "Work at height without a harness: a person worked at the roof edge next to the rooftop units without a harness." Clip attached.

4. 04

   Who is alerted

   The site's safety specialist, instantly.

5. 05

   What the shift and zone pattern shows

   Asked in plain language — "show harness-free work at height on the roof this month" — the event memory returns a short list. The flagged events cluster at one point on the edge — the spot where tools and parts are lowered to the ground — and each lasts only a few minutes, during short jobs.

6. 06

   Corrective action

   Diagnosis: the roof has no safe way to lower tools, so short trips to that point are made without a harness. A recommendation for the facility manager, with the regulatory reference: edge protection where tools are lowered, a hoist instead of hand-to-hand lowering at the edge, and a harness and anchor check in each crew's start-of-day briefing.

Example 3: crossing the crane bay during a lift

1. 01

   Moment

   A steel fabrication hall, 10:15, during a lift with the overhead crane. A camera covers the bay.

2. 02

   What the camera shows

   The lifting zone is marked with barrier tape. While a beam is in the air, two workers step under the tape and cross the bay beneath the path of the load to reach the welding stations on the other side.

3. 03

   The finding + evidence clip

   "Unauthorized entry into the lifting zone during a lift: two people crossed the bay under the path of the suspended load." Clip attached.

4. 04

   Who is alerted

   The production shift supervisor, instantly; the event also appears in the bay's weekly zone score.

5. 05

   What the shift and zone pattern shows

   Flagged events in this bay fall in the morning shift, when lifts and material runs to the welding stations overlap.

6. 06

   Corrective action

   Diagnosis: a scheduling gap — the morning lifts are timed during the material runs to the welding stations, when people need to cross the bay. Recommendation: schedule lifts outside the material runs, and mark a walkway around the bay.

Example 4: night-time entry into an out-of-service tank

1. 01

   Moment

   A chemical plant's tank farm, 22:30, night shift. A camera covers the manway platform of a storage tank taken out of service for cleaning.

2. 02

   What the camera shows

   A person climbs to the platform, opens the manway cover, leans in and then climbs inside. No equipment is set up at the manway, and no cleaning work is under way.

3. 03

   The finding + evidence clip

   "Entry into a confined space with no planned work visible: a person entered the out-of-service tank through the manway on the night shift." Clip attached.

4. 04

   Who is alerted

   The night-shift supervisor, instantly, so that someone can go to the tank.

5. 05

   What the shift and zone pattern shows

   The event memory shows two earlier entries at the same manway during the cleaning week, both at night.

6. 06

   Corrective action

   The safety team checks the entries against the permit log. Recommendation for the plant manager, with the regulatory reference: lock and tag the manway whenever no permitted work is under way in the tank, and brief the night shift on why the tank is off limits.

How Primarch's OHS Expert helps

This section is about our product. The OHS Expert is the Primarch expert module that reads the floor like a safety professional, on the cameras a site already has. For restricted zones and work at height it:

• Tells unauthorized entry apart from permitted maintenance in robot cells, electrical rooms, lifting zones, chemical areas and confined spaces, where a camera covers the entry.
• Catches harness-free work at height at the level of the action, on roofs, mezzanines, platforms and high racking, where a camera covers the working area and its edge.
• Judges missing protective equipment against the zone and the task: a visitor and a technician are not the same thing.
• Narrates each finding in natural language, with a time-stamped evidence clip, and recalls past repeats of the same scene from memory.
• Chains events by shift, zone and time and diagnoses why they repeat — an attention lapse or a process gap.
• Writes corrective actions in the language an inspector would use, assigns owners, and prepares regulation-referenced records, weekly zone safety scores and executive summaries.
• Needs no rule set. It comes pre-configured with OHS domain knowledge and regulation; site-specific thresholds are tuned together at onboarding, and situations nobody wrote a rule for are still caught through scene understanding.
• Checks whether a harness is attached to an anchor point or lifeline, not only whether it is worn, where the camera shows the attachment.
• Checks whether an attendant is present outside a confined-space entry while someone is inside, where a camera covers the entry.

Because it reads the scene in context, it is designed to remove the biggest source of noise in classic systems — rules firing without context — and multi-stage validation and temporal noise suppression are added on top.

Putting it to work

1. 01

   Connect

   Connect your existing RTSP cameras; no new cameras or special hardware.

2. 02

   Pilot on your own site

   Pilots typically start with a single zone and a few cameras — an electrical room door or a roof, say. Thresholds are tuned to your site together, and you review the findings with your safety team.

3. 03

   Roll out

   Scale facility-wide as the system proves out, with dozens of streams watched in parallel.

• Alerts, digests and dashboards. Instant notifications, periodic digests and role-based dashboards, so each finding reaches the person who acts on it.
• Ask the past in plain language. Findings are written into a queryable event memory: "Which entries into the tank farm were recorded on the night shift last week?"
• Records you can defend in an audit. Every finding carries its time-stamped clip; reports carry the regulatory reference and the corrective action with its owner.
• Privacy by design. Footage is anonymized in a GDPR-compliant way, and the system is designed to report risky situations and process gaps, not individuals. With on-premise deployment, footage never leaves the facility, and, where a site requires it, the system can run on air-gapped networks.