A cold store breaks PPE detection in three ways that a normal factory floor never does. The lens fogs when the dock door opens, the freezer aisle sits below the light level the models need, and the housing itself is often outside its rated operating temperature. All three are site conditions, and all three are visible on a drawing before anyone buys a licence.
The camera fails before the model does
ARSA-CVS-001, the camera and site requirements standard, states what every analytic function needs from the image. Helmet detection needs 262 pixels per metre at the point of detection and a minimum of 50 lux at the target plane. Hi-vis vest detection needs 153 PPM and the same 50 lux, with white light rather than infrared, because infrared produces a monochrome image and a colour rule cannot survive that.
Those numbers are not harder to meet in a cold store because the room is cold. They are harder to meet because of what cold room design does to light, to optics, and to where a camera can physically live. IES RP-44, the illumination guidance for warehouse and storage facilities, puts rack face illuminance in coolers around 150 to 200 lux and in freezers around 100 to 150 lux, measured vertically at the rack face. That is above the 50 lux floor at the rack, and it is frequently below it in the aisle centre and at floor level, which is exactly where a person walks through a detection zone. Lighting in freezer aisles is also commonly on occupancy control, so the measured value at 3 a.m. with one operator on a reach truck differs from the value during a site visit at noon.
Three conditions to record before specifying anything
Condensation at the thermal boundary
Fogging happens when the coldest surface inside the housing falls below the dew point of the air trapped with it. An IP66 seal keeps out dust and water jets and does nothing about water vapour that was sealed in during installation or drawn in as the housing breathes through its temperature cycles. The severe case is the dock door and the vestibule, where humid ambient air meets freezer air several dozen times a shift. A camera in a stable minus 22 degree aisle often stays clear for months. A camera two metres inside the door strip curtain fogs daily. Housing heaters help, and they raise the enclosure above dew point only while powered, which means a power interruption is followed by a fogged lens at exactly the moment recorded evidence matters.
Light that is dim, cold in colour, and switched
Freezer fixtures are typically 4000K to 5000K LED, chosen for cold start behaviour rather than for colour rendering. Combined with a low absolute level, this shifts the appearance of a yellow or orange vest enough to matter, and it forces the camera into a long exposure unless the minimum shutter is set manually. A long exposure smears a walking operator across several frames, and a smeared torso does not carry 153 pixels of usable vest.
An operating range the housing may be outside
The ARSA camera specification calls for IP66 and an operating range of minus 10 to plus 50 degrees Celsius, with minus 20 to plus 60 as the recommended figure. A chilled room at 2 to 8 degrees is inside that range comfortably. A blast freezer at minus 25 degrees or colder is outside even the recommended figure, and a standard camera placed there will run out of specification whether or not it produces a picture for a while.
What each zone in a cold store actually allows
| Zone | Typical temperature | Typical light at floor | Helmet detection at 262 PPM | Vest detection at 153 PPM |
|---|---|---|---|---|
| Receiving dock and apron | Ambient to plus 12 C | 200 lux or more, often mixed daylight | Workable. 6.3 m on 2 MP, 8.4 m on 4 MP | Workable. 10.9 m on 2 MP, 14.5 m on 4 MP |
| Vestibule or anteroom | Plus 5 to minus 5 C | Usually above 50 lux, continuous | Workable, condensation is the constraint | Workable, white light required |
| Chilled room, 2 to 8 C | Inside camera rating | 150 to 200 lux at rack face, lower in aisle | Workable if standoff is short | Workable, verify colour rendering |
| Frozen aisle, minus 18 to minus 25 C | Below recommended rating | 100 to 150 lux at rack face, switched | Requires rated housing and measured light | Requires white light, colour analytics degrade |
| Blast freezer, below minus 25 C | Outside rated range | Low, intermittent occupancy | Out of scope for a standard camera position | Out of scope |
The reference case ARSA warrants against is a 3.5 metre mount at 6.0 metre standoff with 22 degrees of tilt, presenting the helmet and vest front to the sensor. Cold store racking rarely offers that geometry inside the aisle, because the mount goes high to escape reach truck masts and pallet overhang, and a high mount forces a steep tilt. Above 45 degrees below horizontal, PPE analytics are prohibited outright, because the wearer’s own hard hat brim hides the face and the vest front is foreshortened to a handful of pixels. The lens and field of view visualiser will show whether a given mount height and standoff clears that ceiling before anyone climbs a ladder.
Cover the boundary, not the aisle
The productive answer in most cold stores is to detect at the point of entry. PPE compliance in a freezer is a boundary condition anyway: the operator either walked in wearing the insulated coverall, the hard hat and the vest, or they did not. A camera in the anteroom, looking at the approach at 6 metres and 22 degrees under continuous white light, meets the published requirement without any exotic hardware. A camera 40 metres down a switched-light frozen aisle usually cannot, and dressing it in a heated freezer housing does not change the pixel density or the tilt.
That reframing also lines up with how the AI Box appliance is sized. A three-camera Mini at a single freezer entry, or one 25-camera Server covering every dock, vestibule and anteroom on a site, covers the compliance question with cameras in positions that can actually be warranted.
The limits worth stating plainly
Basic Safety Guard detects helmet, hi-vis vest and safety boots present or absent, plus hazard zone entry. It does not detect whether a garment is freezer rated, whether an insulated coverall is fastened, or whether a worker has exceeded a safe exposure time in a subzero room. Cold stress management under OSHA 29 CFR 1910.132 remains a procedural control, and this system contributes an entry log to it rather than a substitute for it.
A hi-vis vest worn underneath an insulated jacket will not be detected, correctly so, because it is not visible. Sites that want vest compliance in the cold need high visibility outerwear, which is why high vis insulated coveralls exist as a product category. Colour coded rules of any kind stop working under infrared illumination, and infrared is a common default for the unlit corners of a dock apron.
Detection also runs on the appliance inside your network. Footage of your operators does not leave the site, and what crosses the network is event metadata and, where you enable it, a cropped snapshot.
FAQ
Can PPE detection run inside a freezer at minus 25 degrees Celsius?
Not with a camera at the standard specification, which is rated minus 10 to plus 50 degrees, or minus 20 to plus 60 as the recommended figure. A freezer rated or heated housing is required, and the light level and mounting geometry still have to be verified separately. In most cold stores the compliance question is better answered at the entry, where a standard position meets every requirement.
Why does the camera fog when the dock door opens?
Because humid ambient air meets a surface colder than its dew point. An IP66 seal blocks liquid water and dust and does not block water vapour. Heaters keep the lens above dew point while they have power. Positions at a thermal boundary should be treated as the difficult ones on a site, and positions deep in a stable cold room as the easy ones.
Will helmet detection work under freezer aisle lighting?
Only where 50 lux is present at the target plane while the analytic is expected to work. Freezer aisle lighting is often occupancy switched and often measured at the rack face rather than at floor level in the aisle centre. Take the reading where the person walks, at the time of day the zone matters, with the lights in their normal state.
Does a beanie or a thermal balaclava register as a hard hat?
No. The 262 PPM requirement exists specifically to resolve the structural difference between a hard hat shell and soft headwear, so a knit cap or hood under a helmet reads as what it is. This does mean the pixel density has to be met. At 96 PPM the distinction is no longer present in the image and no amount of tuning recovers it.
What happens to a zone if the racking changes?
Accuracy attaches to detection zones recorded as ACCEPTED in the Site Acceptance Record. If a camera is moved, lighting is altered, or new racking obstructs the view, those zones revert to unaccepted status until re-surveyed. Cold stores reconfigure often, so it is worth naming who owns that notification.
How do we find out before committing budget?
A Remote Camera Design Review costs $1,500 and returns a pass or fail against every requirement for up to 20 cameras in about a week. Where a site needs measured lux readings and mounting checks in the rooms themselves, the On-Site Camera Survey is $4,500 plus travel for up to 50 cameras. Either fee is deducted in full from the project if you contract within 90 days. The full list is on services.
Start with the positions, then the licences
A cold store is one of the few site types where the honest answer to “can you detect PPE here” depends entirely on which door you are standing at. Get the boundary positions surveyed, and the rest of the deployment behaves like any other industrial site.
See what Basic Safety Guard detects and how it is licensed, then book a design review against your own camera schedule.