What Is the Purpose of Sensors in Perimeter and Building Security?

Security alarms, CCTV cameras and perimeter security systems all have one thing in common – they are designed to prevent intruders from accessing your property or site. To function, alarms need to have a form of sensor which triggers the alarm or alert based on a movement or activity, such as the presence of a person, tripping an alarm on a closed door, or breaking glass.

While there are myriad types of building and perimeter security systems, all must incorporate sensors that can detect motion, tampering, or the presence of a vehicle and differentiate these triggers from naturally occurring noises or movement due to wind, rain or wildlife, for example.

In this article, we’ll explain how different types of security detectors work and the purpose of sensors in devices and alarm systems you might consider installing to reinforce the security of your premises.

Perimeter and Building Security Sensors Explained

As we’ve indicated, there are numerous sensors that function based on variable parameters. Most advanced security systems can be programmed according to your requirements, ensuring that your alarms or surveillance networks will only sound an alarm, transmit an alert notification or inform your security response team when a defined activity occurs.

That could include:

• Detecting an approaching vehicle to the rear of your site perimeter.
• Identifying a person or several people outside of opening hours.
• A door, window or lock being opened, or a seal being broken.
• The presence of smoke, heat, water, fire or gas.
• Automatic alarms if a device is moved, disturbed or otherwise interrupted.

Sensors can be activated based on sound, movement, vibration, temperature, or more technical parameters such as body heat signatures – depending on the most prevalent risks and the nature of your business or building.

They are also used for non-security purposes, such as determining where a member of staff is, or monitoring personnel for productivity or PPE compliance tracking.

Why Do Perimeter and Building Security Systems Rely on Sensors?

In the vast majority of scenarios, it is impossible for on-site security guards to have 24/7 visual sight of every part of your premises. Security patrols, access controls, gated barriers and staffed entry points are certainly great ways to improve security safeguards but cannot provide 100% coverage of each potential entry point.

For example, if a compound has perimeter fencing around the boundary and a gated entrance point staffed by a trained security guard, any authorised visitors will have their credentials verified before being permitted entry, and it is unlikely personnel will ever attempt to enter the site from any other point.

However, an intruder could scale a wall, cut through a fence, or use force to access the site from the furthest point away from the guarded station without being detected, seen or apprehended.

While this is a simplified illustration, it demonstrates why sensors are so vital. Surveillance and alarm systems rely on having a method of detecting unusual or suspicious activity to direct security teams to investigate.

In short, an advanced alarm system equipped with sensors acts as an always-on security guard and will raise the alert immediately when anything outside of the norm happens and requires further action.

Types of Alarm System Sensors

Each security device or installation works differently, and the most suitable sensors for your property or business depend on a thorough, professional risk assessment. This appraisal process helps security consultants determine where your greatest risks lie and recommend the best ways to mitigate or prevent them from occurring.

As a few examples:

• Motion detectors use infrared technology to detect movement, which can be customised to disregard movement beneath a certain size to eliminate false alarms caused by local wildlife.
• Environmental detectors can pick up changes to air quality, such as ash particles, or other factors like water, gas and chemicals.
• Vibration detectors often work based on algorithmic analysis, which can assess whether vibrations are caused by a person climbing, walking or crawling, a vehicle, or another suspicious activity such as cutting through wires or fencing.
• Glass break detectors are commonly installed on windows and within entrance doors to raise the alarm when the surface is broken – a similar technology is used within door or window alarms where the alarm will sound if the two parts of the sensor are disconnected.

Many of these security detection sensors use infrared light to identify movement in any low-light settings, including overnight and away from light sources. Adding additional functions such as photo verification or correlation analysis can further improve the accuracy of your alarm sensors, where devices act in real time to compare signals and determine whether there is a live incident underway.

Daniel Meeajane

Business Development Director, Clearway

Daniel Meeajane

Advanced security systems can be programmed to detect specific activities such as approaching vehicles, unauthorized personnel outside opening hours, or environmental hazards like smoke and heat, ensuring alarms only trigger on defined events rather than false alerts from natural occurrences.

Choosing the Right Perimeter and Building Security Alarm Sensors

Every building, premise or business will benefit from an initial security evaluation to ensure you target your resources efficiently and determine the ideal placements and functions of your alarm sensors.

Below, we’ve summarised some of our most in-demand security devices and systems to clarify how they work and the sensors integrated into each solution.

inView Detect Perimeter Security

This wireless intruder detection system is portable and accessible and can be used in any position or placement where you have an elevated threat level. Operating with an autonomous power system, inView Detect is rapidly deployable and can be used in any environment, from a construction site to open land, to protect specific assets or items of equipment or positioned in a network around a wider perimeter.

Each intrusion detection unit offers 360-degree coverage and activates an alarm according to your security protocols when movement is detected, excluding triggers up to 80cm tall to eliminate false callouts.

Commercial Intruder Alarms

Our range of commercial intruder alarms is suited to any business or site, with a number of devices and integrated units that can identify movement, unexpected entry, fire and smoke, or when an item of equipment or machinery is moved or absent.

Depending on your programmed parameters, your intruder alarm can notify responders when a person is detected inside the perimeter, when a vehicle approaches an unauthorised entry point, or when any activity occurs when the site is not expected to be in use.

Each of these solutions incorporates advanced, customisable sensors and ensures that if anything untoward or suspicious occurs, you can react swiftly, with the flexibility to arm, disarm or remote access your security systems at any point.

Written by Daniel Meeajane

Business Development Director, Clearway Fire and Security

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Daniel Meeajane is Business Development Director at Clearway Fire and Security, bringing strong commercial expertise alongside a detailed understanding of fire protection systems and industry standards.

Having contributed to a number of major projects and delivered successful outcomes, Daniel uses his knowledge and experience to drive awareness of effective fire protection solutions across a wide range of environments. His approach combines relationship-led business development with a clear understanding of technical compliance, operational requirements, and customer risk.

Daniel has a strong understanding of BS 5839-1, recognising the importance of compliant fire detection and alarm system design, installation, commissioning, and maintenance. He also keeps pace with the latest developments in fire technology, ensuring clients benefit from informed guidance, up-to-date solutions, and best practice across every stage of delivery.