Understanding BS 5839-6 and Choosing the Right System for Your Property
Choosing the correct fire alarm system isn’t just about ticking a box—it’s about protecting lives and ensuring your building meets its legal obligations under UK fire safety legislation. But if you’ve ever looked at the British Standard for fire detection systems, you may have come across the terms Grade A, Grade D, Grade F, and so on—and wondered what they actually mean.
In this guide, we’ll demystify the different fire alarm grades as defined by BS 5839-6, and help you determine what grade is right for your building—whether it’s an HMO, office, or care home.
What Is BS 5839-6?
BS 5839-6:2019 is the British Standard that sets out recommendations for the design, installation, and maintenance of fire detection and fire alarm systems in domestic premises. It is commonly used when planning systems in:
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Houses
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Flats
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HMOs (Houses in Multiple Occupation)
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Sheltered housing
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Residential care homes
Although it’s primarily for domestic settings, the grades are often referred to when assessing fire protection needs in mixed-use or complex buildings.
Understanding Fire Alarm Grades (A to F)
Fire alarm grades refer to the level of complexity and reliability of a system—from fully engineered installations to standalone battery alarms.
Here’s a breakdown of each grade:
Grade A
A full fire alarm system with a dedicated control panel, smoke/heat detectors, manual call points, and sounders, designed to be compliant with BS 5839-1 (the standard for non-domestic premises).
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Back-up power supply required
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Often monitored and zoned
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Requires professional installation and regular maintenance
Typical Use:
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Larger HMOs (three or more storeys, five or more occupants)
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Care homes
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Purpose-built apartment blocks
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High-risk domestic environments
Grade C
A system of mains-powered interlinked alarms (smoke or heat), all controlled by a central control unit with back-up power.
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More sophisticated than Grade D, but less complex than Grade A
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Can allow greater control and monitoring than standard interlinked alarms
Typical Use:
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Supported living accommodation
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Larger single-family dwellings where residents are vulnerable
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Some mid-size HMOs where risk justifies additional control
Grade D1
Mains-powered alarms with a tamper-proof, long-life battery back-up. The alarms are interlinked, either wirelessly or via wiring, so when one activates, all sound.
Typical Use:
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Standard HMOs (2 storeys, 3–4 occupants)
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Rented houses and flats
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Family homes
Grade D2
Same as D1 but with a replaceable battery back-up rather than a sealed unit.
Typical Use:
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Lower-risk domestic dwellings
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Older properties being retrofitted with basic detection
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Some single-occupancy rental flats
Note: D2 systems are gradually being phased out in favour of tamper-proof alternatives due to reliability concerns.
Grade F1
Battery-powered alarms with a sealed, tamper-proof battery designed to last the full lifespan of the unit (usually 10 years).
Typical Use:
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Owner-occupied homes with low risk
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Budget-conscious homeowners upgrading from older alarms
Grade F2
Battery-powered alarms with user-replaceable batteries.
Typical Use:
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Temporary or budget installations (not usually recommended for rental properties)
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Single-person dwellings with minimal fire risk
What’s the Right Grade for Your Building?
Houses in Multiple Occupation (HMOs)
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Small HMO (e.g. 2 storeys, 3–4 occupants): Grade D1, LD2 coverage
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Large HMO (3+ storeys, 5+ occupants): Grade A, LD2 or LD1 coverage
Residential Flats
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Individual flats: Grade D1 or D2 (depending on risk and layout)
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Common areas of blocks: Typically require separate fire detection systems compliant with BS 5839-1
Residential Care Homes or Sheltered Housing
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Care homes: Grade A system throughout
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Sheltered housing (general needs): Grade C or D1, depending on vulnerability of residents
Offices and Commercial Premises
BS 5839-6 doesn’t typically apply here. Instead, BS 5839-1 governs non-domestic fire alarm systems. However, the terminology may still be referenced for areas with residential use (e.g. on-site caretaker flats or staff accommodation).
Grade vs Category: What’s the Difference?
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Grade refers to the type of system, based on reliability, complexity, and power supply.
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Category refers to the areas covered and the level of protection (e.g. LD1, LD2, LD3 for domestic systems).
Both need to be considered when designing a fire detection system. For example, a property might require a Grade D1, LD2 system—meaning mains-powered interlinked alarms with sealed battery back-up, covering escape routes and high-risk areas like kitchens.
Final Thoughts
Fire alarm grades may seem complex at first, but understanding them is key to choosing the right system for your property. Whether you’re a landlord, developer, or managing agent, selecting the correct fire alarm grade can help ensure you stay compliant with UK fire safety regulations—and more importantly, keep people safe. For expert advice on fire protection and prevention systems, contact Martyn Young Fireproofing Consultancy today on 07585 896648