Grade 2 vs Grade 3 Intruder Alarms: Which Do You Need?

The short answer

Grade 2 suits most homes and lower-risk businesses. Grade 3 is for commercial premises and higher-value homes where a burglar is likely to know how alarms work and bring tools to beat them. Your insurer will often tell you which grade they expect.

Intruder alarms in the UK are designed to BS EN 50131-1, with the UK rules for applying it set out in PD 6662. The standard sorts systems into four security grades according to the type of intruder they need to stop. In practice almost every system we fit is Grade 2 or Grade 3.

The four security grades

Grade 2 vs Grade 3: the practical differences

Detectors and anti-masking

A common way to beat an alarm is to cover or spray a motion detector while the building is open, so it cannot see anything once the alarm is set. Grade 3 detectors use anti-masking to spot this and report it. Grade 2 detectors do not need to.

Signalling and monitoring

Grade 3 systems need stronger, more frequently checked signalling to an alarm receiving centre (ARC). That usually means dual-path signalling, such as IP plus 4G, so cutting one line does not silence the alarm. Grade 2 systems can be audible only, known as Grade 2X, or monitored, but the signalling requirements are lighter.

Tamper protection and components

Grade 3 control panels, keypads and detectors have tougher tamper protection and need more secure user codes and set/unset methods. Every part of the system has to meet the grade. One Grade 2 detector on a Grade 3 system brings that part of the system down to Grade 2.

Cost

Grade 3 equipment and dual-path monitoring cost more to buy and run than Grade 2. The difference is usually small next to the value of the stock or premises being protected. It is also small next to the cost of an insurer refusing a claim.

Which grade do I need?

The grade should come from a security risk assessment carried out by your installer before anything is quoted. We look at:

As a rule of thumb, most homes and small offices are Grade 2. Shops with stock, warehouses, workshops with tools and plant, pharmacies, and homes with high-value contents are usually Grade 3.

Police response

If you want the police to respond to your alarm, the system must follow the National Police Chiefs’ Council (NPCC) policy. It must be installed and maintained by a company certificated by a UKAS-accredited body such as SSAIB or NSI, and monitored by an approved ARC. In most cases it must also be designed to give confirmed activations to BS 8243. The police then issue a unique reference number (URN) for the system. Repeated false alarms can lead to police response being withdrawn, so good design and maintenance matter.

Servicing

Monitored intruder alarms should be maintained by the installer, normally with two preventative maintenance visits a year. Audible-only systems usually need one. Keeping to this is often a condition of insurance.

Salts Fire & Security is SSAIB certificated for intruder alarm installation and maintenance. We design Grade 2 and Grade 3 systems for homes and businesses from our base in Baildon. See our intruder alarm service, or find us in Bradford, Leeds and beyond.

Common questions

Last reviewed 04/11/2026 by the Salts Fire & Security team, Baildon. This is general guidance; your fire risk assessment and the full standard take priority.