Since the first of October 2005 all new intruder alarm systems must now conform to the latest European standards which supersede the previous British standard BS4737.

Systems are now designed to meet a specific European Grade, rated from 1 to 4.

The grades are designed to combat the technical knowledge of a potential burglar.

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.

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.

Grade 3 is for a reasonably substantial risk property. There is 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.