Screening and metal detection
A walk-through detector with no procedure and no trained officer filters nothing, whatever its setting.
- Parent division
- Physical and cyber security
The problem
A screening point is a layout and a procedure; the equipment is only one part of it.
A walk-through detector signals the presence of metal. That signal is worth something only if someone acts on it: a trained officer, with a hand-held detector, a place to conduct a secondary search, and a written instruction stating what to do with whatever is found.
That is why failing screening points rarely fail because of the equipment. They fail because people flow was never sized and the queue spills outside, because sensitivity was lowered to reduce alarms, or because secondary searches are conducted in the main thoroughfare, with no privacy.
Sizing the flow is the most often neglected point. A screening point designed for less than the real footfall produces a queue, and a queue invariably leads to relaxing the check in order to clear it.
A screening point and what holds it together, schematic
- 01Peak-hour count
- Target throughput is calculated on the peak, never on the daily average.
- 02Queue and divest
- A visible divest area and a sufficient work surface cut alarms without touching the setting.
- 03Walk-through detector
- It signals the presence of metal. That signal is worth only what follows it.
- 04Written instruction
- What the officer does with each category of item, and what they do when entry is refused.
- 05Secondary search
- Out of public view. Conducted in the thoroughfare, it is cut short out of awkwardness and the post becomes a formality.
- 06Controlled exit
- A route separate from the entry queue, failing which the point congests itself.
Scope
What the service covers
- Flow study
- Entry counts at peak hours, target throughput, number of lanes, queue layout, and handling of peaks and exceptional entries.
- Screening point layout
- Detector position relative to the entrance, divest area, work surface, a secondary search area out of public view, and a separate exit route.
- Detection equipment
- Multi-zone walk-through detectors, hand-held detectors, bag inspection, handling of site electromagnetic interference, and backed-up power for the post.
- Procedures
- Written secondary search instructions, handling of prohibited items, special regimes, conduct when entry is refused, incident log and escalation.
- Officer training
- Daily setting and verification of the equipment, search technique, dealing with the public, periodic exercises and assessment.
- Integration with the wider system
- How the point works with access control, video surveillance and the guard post, a shared clock, retention of recordings and traceability of refusals.
Situations
The most frequent situations
- Busy public building
- Throughput determines everything. An undersized point creates an outdoor queue, which itself becomes the vulnerable part of the arrangement.
- Diplomatic mission or protected site
- Low flow, high requirement, distinct regimes by visitor category, and close working with the guard post.
- Industrial or mining site
- Entry and exit control, disturbed electromagnetic environment, and staff wearing metallic protective equipment.
- Event or temporary entrance
- A point set up for a limited period. The constraints are power, signage and training officers who will not operate the point for long.
Requirements
What to require, of us as of anyone
These requirements hold whichever supplier is appointed. Written into a tender, they filter out the responses that will not hold.
- The target throughput and a real entry count at peak hour, before any equipment is chosen.
- A secondary search area out of public view, without which searches will not be conducted properly.
- A written procedure stating what the officer does with each category of item found.
- Daily verification of equipment settings, recorded in a register.
- Initial training and periodic practice for officers, with assessment.
- Backed-up power for the post, failing which it disappears with the mains.
- Traceability of refusals and incidents, and the link between it and video surveillance of the entrance.
Pitfalls
Common mistakes, and what they cost
- Lowering sensitivity to reduce alarms
- It is the most common drift, and it empties the post of its function. The right answer to a high alarm rate is a change of layout and a divest instruction, not a lowered setting.
- Sizing the point on the average
- The daily average says nothing about the peak. A point that is adequate on average and saturated every morning will be bypassed, opened or relaxed at exactly the hours it would serve most.
- Conducting secondary searches in the main thoroughfare
- With no dedicated area, the search is cut short out of awkwardness, for the officer as much as for the person searched. The post becomes a formality.
- Buying the equipment before writing the procedure
- The procedure determines the number of lanes, the layout and the staffing. Decided after purchase, it adapts to the equipment rather than to the need.
Questions
Questions asked before consulting
How many screening lanes are needed?
The number follows from the target throughput and the average time to process one person, measured at peak hour rather than as a daily average. The calculation must include secondary search time, which affects a non-negligible share of passages. An extra lane costs less than a queue that leads to relaxing the check.
How can the number of alarms be reduced?
Through layout, not through settings. A visible divest area, clear signage on what to remove and a sufficient work surface cut alarms sharply without touching sensitivity. Lowering sensitivity produces the same comfort by removing the point’s function.
Should bags be inspected?
It depends on what the point is meant to prevent. A walk-through detector only addresses what a person carries on them; bags placed aside escape it. A coherent arrangement addresses both, or explicitly accepts not addressing bags, which is a decision rather than an oversight.
What training do officers need?
Daily verification of the equipment, secondary search technique, conduct when entry is refused, and dealing with the public, which is the main day-to-day difficulty. Initial training is not enough: periodic practice is required, failing which practice drifts within months.
What happens to items removed?
The procedure must cover each category: return on exit, deposit, seizure, or calling the authorities. A post with no written instruction on this improvises, and improvisation becomes contestable. The register of removed items is part of the arrangement.
Does screening replace access control?
No, the two answer different questions. Access control determines who enters; screening determines what enters. A serious site does both, with a shared clock allowing a passage, an alarm and the matching video recording to be reconciled.
Neighbouring subjects
Solutions concerned
Consultations · Pre-qualifications · Partnerships
Let us discuss the actual case.
Describe the site, the dominant constraint and the deadline. We will say what requires a preliminary study and what can be committed directly.