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EN 50131 European Standards for Intruder Alarm Systems

EN 50131 was phased in to replace British Standards BS4737, BS7042 and BS 6799 and was adopted in October 2005 utilizing PD 6662:2004, an enabling document which facilitated the introduction of EN 50131 into the UK.

The difference between PD6662 / EN 50131and the old British Standards

PD6662 differs from former British Standards in the following ways:

  • It determines not only the system but also the component design requirements for Intruder and Hold-up Alarm systems.

  • A comprehensive Risk Assessment is required to determine the design criteria of the system.

  • Applicable to both hard-wired and wireless installations.

  • Grading of systems is required to reflect “the risk”. I.E. Grade 1 – Low Risk, Grade 4 – High Risk.


Does my existing system need to be upgraded to comply with PD6662?

If your current system complies with the old British Standards and is working effectively changes are not required.

If any upgrade to your system is undertaken your insurance company will require the system to comply with PD6662.

If you lose Police Response and the URN is withdrawn it can only be reinstated if the system is upgraded to comply with PD6662.

Security Grades

One of the most important aspects of the EN 50131 requirements is the concept of a security grade. For each installation, the grade of the system has to be chosen according to various factors. The EN the grade is described in terms of the type of intruder and how much effort they would put into a burglary.

What are the Grades?

Grade 1 is for an installation with a low risk of theft. The property is not likely to attract intruders. It is assumed that a thief is likely to be opportunistic rather than bothering to plan things in advance. In the application guide (DD CLC/TS 50131-7) it assumes that an intruder is simply going to break open a door.

Grade 2 is for a slightly higher risk of theft. The property is likely to have something of interest to an experienced thief. In this case, the intruder is expected to have some knowledge of how alarm systems work and possibly carry some tools to allow him to overcome a simple alarm system. The thief is likely to check the building for ease of access through doors, windows and other openings.

Grade 3 is for a reasonably substantial risk property. There is a good reason to assume it may be broken into and might well contain objects of high value. An intruder is likely to gain access by penetrating doors, windows or other openings. The thief could be very experienced with intruder alarm systems and possess a number of tools and equipment to overcome the system

Grade 4 is for very high-risk properties. Intruders could be expected to plan a burglary in advance and have the knowledge and equipment to alter parts of the intruder alarm system to prevent detection. It is assumed that the intruder could gain access by penetration of floors, walls and ceilings. The intruder is unlikely to be working alone.



What Grade of System does my installation need?

This is difficult to say at the moment and opinion on this matter varies from country to country. The view in the UK tends to require grades that are higher than other countries (e.g. a shop in Belgium at grade 2 could be grade 3 in the UK). To a large degree, the choice of grade would be guided by insurance companies. A typical view though could be:


  • Grade 1 would only be of interest in domestic properties (without an insurance requirement for an alarm system).

  • Grade 2 would be most domestic properties and low risk commercial (e.g. florists)

  • Grade 3 would be for high-risk domestics and most commercial properties (e.g. Newsagent with cigarette sales)

  • Grade 4 would be for extremely high-risk domestic and higher risk commercial properties (e.g. bullion stores).


Mixing Components of Different Grade

The EN standard says that it is not necessary to use the same grade of component throughout an intruder system.

If the installation is a grade 2 then there is no problem using, for example, a grade 3 power supply.

If however, an installer fits a grade 2 component (such as a detector) in a system then that system is limited to grade 2 at best.

It is possible to have a defined part of a system at a higher grade so long as all associated parts are at the same (or higher) grade. For example, a system combining intruder and hold-up (PA) functionality could have a grade 4 hold-up system whilst the intruder parts were limited to grade 3. But this example is only valid if the power supply, alarm transmission system and warning devices used by the hold-up (PA) parts are all grade 4. This would still allow intruder parts such as PIR’s to be grade 3. The system as a whole is, of course, only grade 3.



R​​isk Assessment

One of the most significant issues within the new EN standards will be evaluating the risk associated with the premises and determining a grade of system. This is because once the grade of a system is determined it will define the extent of the system, its signalling and tamper security requirements.


Grade 1

Systems classified as Grade 1 would be most at risk from ‘Opportunist’ thieves.

Intruders would have little knowledge of Intruder Alarm Systems and would be restricted to a limited range easily available hand tools, such as hammers, chisels, screwdrivers, pliers etc.

This grade would typically be used for most domestic ‘Bells Only’ Systems.

This grade is a lower standard than BS 4737.

Grade 2

Systems classified as Grade 2 are likely to be targeted by criminals who will have prepared themselves prior to the crime and will know something about the contents of a building.

Intruders would have limited knowledge of Intruder Alarm Systems and would have the use of a general range of tools and portable instruments such as multi-meters bolt cutters, battery drills etc.

This Grade would normally account for large residential and small commercial systems such as Florists, Bakers, Salons and Carpet Retailers.  Grade 2 is the closest to BS 4737.

An option has also been created for lower risk Grade 2 Systems, which are not monitored.

These are classified as Grade 2X.

Grade 3 / 3+

Systems classified as Grade 3 are likely to be required when the contents of a building are perceived to be high value, and criminals are likely to spend their time planning an intrusion.

Intruders would be conversant with Intruder Alarm Systems and have a comprehensive range of tools and portable electronic equipment, such as oscilloscopes, laptops, security screwdrivers etc.

Typically, this grade would account for most commercial systems such as bonded warehouses, motor garages, computer distributors, mobile phone shops, and should be the expected Minimum for Banks, ATM Machines, Strongrooms,

Grade 4

Systems are classified as Grade 4 will apply where security takes precedence over all other factors.

Intruders are expected to have the ability or resource to plan an intrusion in detail and have access to a full range of tools and equipment.

This would include the means to substitute vital components in the Intruder Alarm System.

Typically, this grade accounts for security systems that could be applied to military installations, bullion and cash centres, government research establishments etc. 

In these circumstances there is a high risk of organised crime or terrorism.

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