General guidance only. Check the standard itself and take advice from your own competent person for the job in front of you. Last reviewed 22 October 2026.
What a grade is
The BS EN 50131 series grades an intruder alarm system by the kind of intruder it is designed to resist. PD 6662 explains how those European standards are applied in the UK. The higher the grade, the more skill, knowledge and equipment the system assumes an intruder may have.
| Grade | Intruder assumed | Typical use |
|---|---|---|
| 1 | Little knowledge of the system and a limited range of tools. | Low-risk premises and some homes. |
| 2 | Some knowledge, using general tools and some specialist equipment. | Many homes and smaller commercial premises. |
| 3 | Good knowledge of the system and a comprehensive set of tools, including portable electronics. | Larger homes and most commercial premises. Insurers often ask for it. |
| 4 | Able to plan in detail, with the full range of equipment and the means to substitute vital components. | The highest-risk sites. |
The system takes the grade of its lowest-graded component, so a grade 3 control panel with grade 2 detectors is a grade 2 system. The grade should be chosen from a risk assessment and written into the specification. Insurers set their own requirements, so check the policy wording before you design.
Police response
Police response is not automatic. Under the National Police Chiefs' Council (NPCC) requirements, the system must be monitored by a recognised alarm receiving centre, the installer and maintainer must be certified by a UKAS-accredited body, and the police force issues a unique reference number (URN) for the premises. Without a valid URN, an activation is treated as unconfirmed and will not get a police response without evidence of an offence in progress.
A few details worth knowing when you talk to a customer:
- The premises need at least two keyholders who can attend the premises within 20 minutes.
- Police response can be withdrawn after repeated false calls. In the version of the requirements we checked, written notice is sent at two false calls in 12 months and response is withdrawn at three.
- To restore it, the cause has to be identified and fixed and a period free of false calls achieved, unless extra confirmation is added.
Police policy is reviewed from time to time, so use the current document and the force's own guidance for anything you put in a contract.
How often should an intruder alarm be maintained?
The expected number of visits depends on the grade, the type of signalling and the scheme the installing company is certified under. As a guide, NSI's member guidance table for the PD 6662 and BS EN 50131 grades sets out two visits a year for grades 2, 3 and 4. For grades 2 and 3, one of those can be a remote check if the equipment supports it, and lower-risk systems may need only one visit a year. Systems with remote signalling to a monitoring centre are generally expected to have two visits a year.
BS 9263 covers commissioning, maintenance and remote support of intruder and hold-up alarms and is the document to read for the detail. Your certification body, the police requirements and the customer's insurer may each ask for more than the minimum, so agree the visit pattern in the maintenance agreement rather than assuming.
When there is a fault, the maintainer is expected to attend as soon as practicable. Under NSI's scheme document that means within four hours, or before the system next has to be set if that is later.
What a maintenance visit covers
- Control equipment, power supply and standby battery, with readings recorded.
- Detectors, contacts and keypads operated and recorded.
- Sounders and strobes, tamper protection and any hold-up devices.
- The signalling path to the monitoring centre, tested end to end where fitted.
- A look at the premises for changes, such as new rooms or blocked detectors, and at the event log for repeat false alarms.
- Customer instructions refreshed and keyholder details checked.
Common questions
What do intruder alarm grades 1 to 4 mean?
The grades in the BS EN 50131 series describe the intruder a system is designed to resist, from grade 1 for little knowledge and limited tools to grade 4 for detailed planning and full equipment. The system takes the grade of its lowest-graded component.
What grade of intruder alarm does a business need?
It depends on a risk assessment and the insurer. Many commercial premises specify grade 2 or 3, and insurers often ask for grade 3 where an alarm is a condition of cover. Check the policy wording.
How often should an intruder alarm be serviced?
NSI's member guidance table sets two visits a year for grades 2, 3 and 4, with one of them allowed to be a remote check for grades 2 and 3 where the equipment supports it. Check the requirements of your certification body, the police force and the insurer.
What is needed for police response to an intruder alarm?
The system must be monitored by a recognised alarm receiving centre, installed and maintained by a company certified by a UKAS-accredited body, and the police force must issue a unique reference number for the premises.
How Compliar helps
Compliar's Intruder Alarm Periodic Maintenance Report is referenced to the BS EN 50131 series and PD 6662, and the template records the security grade of the system (grade 1 to 4) next to the equipment and test results. Alarm monitoring details for a site, including the alarm receiving centre's name and number, are kept with the site.
- Maintenance plans on a quarterly, six-monthly or annual cycle, scheduled against the property (maintenance plans are on Office seats and above).
- Equipment records per site, so a visit starts from the last one.
- Defects raised against the failed device and turned into a quote.
- Reports sent to the customer as branded PDFs when the engineer finishes.
Less paperwork. More progress.
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