Intruder alarm security grades explained
Security grades
The grade says what kind of intruder the system is designed to resist. A higher grade means a more capable intruder.
| Grade | Risk | The intruder |
|---|---|---|
| 1 | Low | Expected to have little knowledge of intruder and hold-up alarm systems, and to be limited to a small range of easily available tools. |
| 2 | Low to medium | Expected to have limited knowledge of these systems, and to use a general range of tools and portable instruments. |
| 3 | Medium to high | Expected to be conversant with these systems, and to have a comprehensive range of tools and portable electronic equipment. |
| 4 | High | Used when security takes precedence over all other factors. |
Environmental classes
The class says where the equipment is meant to be installed.
| Class | Where |
|---|---|
| I | Indoors, where the temperature is well maintained. +5 to +40 °C. |
| II | Indoors, in general areas such as corridors and unheated stores, where condensation is possible. −10 to +40 °C. |
| III | Outdoors, sheltered. −25 to +50 °C. |
| IV | Outdoors, general. −25 to +60 °C. |
The grade wording follows a national adoption of BS EN 50131-1 (clause 6), and the temperature ranges are from its clause 7. Check the current edition, BS EN 50131-1:2006+A3:2020, for the exact wording.