LD1, LD2 and LD3 fire alarm coverage
LD1, LD2 and LD3 are domestic life-safety coverage categories used with BS 5839-6. They describe extent of automatic detection and are separate from system grade.
Reviewed: 20 August 2026
This guidance is general information. The correct fire safety measures depend on the premises, its use, occupants, fire risk assessment and applicable legal duties.
LD1
LD1 is the broadest of the three domestic life-safety coverage categories, providing automatic detection throughout relevant areas subject to the detailed standard recommendations.
LD2
LD2 adds detection in specified higher-risk rooms or areas to escape-route coverage.
LD3
LD3 is centred on circulation spaces forming escape routes and provides less extensive coverage than LD1 or LD2.
Read grade and category together
A statement such as Grade D LD2 contains two different pieces of information: system grade and detection coverage category.
Frequently asked questions
Is LD1 better than LD2?
LD1 provides broader coverage, but the correct category is the one justified by the premises and risk.
Is LD2 a grade?
No. LD2 is a coverage category; grade describes the system arrangement.
Sources and further reading
For legal duties and technical standards, use the current primary source and professional advice where required.