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Intruder Alarm Grades
Grades 1–4 per PD 6662 / BS EN 50131 and the risk level each is designed to resist.
| Grade | Designed against | Typical premises |
|---|---|---|
| 1 | Low risk — intruders with little knowledge of intruder alarm systems and limited tools. | Domestic premises with a low theft risk and no insurer or police requirement for a graded system. |
| 2 | Low‑to‑medium risk — intruders familiar with alarm systems, using some tools and portable equipment. | Most domestic properties and low‑risk commercial premises such as small shops and offices. |
| 3 | Medium‑to‑high risk — experienced intruders with a comprehensive range of tools and portable electronic equipment. | Higher‑value commercial premises — retail, offices — with a substantial risk profile. |
| 4 | High risk — intruders with the resources to plan an attack in detail, including substitution equipment. | High‑security or life‑safety‑critical sites, such as banks, bullion stores, jewellers and government or classified premises. |
Police URN registration for a monitored response is generally only granted where the system is installed to at least Grade 2, with Grade 3 common practice for higher‑risk commercial sites. Grade 1 systems aren't normally accepted for URN registration. See our ARC monitoring page for what URN registration involves.
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