With updates occurring every 5 to 10 years, or whenever significant changes arise, we could not be more excited that Linear Heat Detection (LHD) features prominently in the latest BS 5839-1:2025 standard. This simple yet effective form of specialist heat detection is ideal for use in hard-to-maintain environments, and the updated standard specifically highlights the latest Linear Heat Detection standards, BS EN 54-22 and BS EN 54-28.
Overview of BS 5839-1:2025
Published by the British Standards Institution (BSI) on April 30, 2025, the BS 5839-1:2025 standard aims to support fire evacuation strategies through well-designed fire detection and alarm systems.
This update, coming eight years after the last iteration, has been warmly received by the industry and facilities managers alike. It covers various aspects, including the design, installation, commissioning, and maintenance of these systems, ensuring their effectiveness in non-domestic premises.
To read a comprehensive guide on the entire standard, you can download it here: Guide-to-the-changes-in-BS-5839-1-2025.pdf
This article focuses on the key aspects of linear heat detection or line-type heat detection as outlined in the document (but without the legions of text)…
Key Sections Relevant to Linear Heat Detection
- Linear Heat Detecting Cables: The standard specifies that linear heat detecting cables should conform to BS EN 5422 or BS EN 5428.
BS EN 54-22:2015+A1:2020 specifies requirements, test methods, and performance criteria for resettable line-type heat detectors used in fire detection and fire alarm systems. These detectors are designed to detect heat along their length and are particularly useful in environments where point detectors may not be practical.
BS EN 54-28:2016 outlines the requirements for non-resettable line-type heat detectors It focuses on ensuring that these detectors are effective in detecting heat and providing timely warnings in various environments.
These cables are crucial for detecting heat along their length and are particularly useful in environments where point detectors may not be practical.
- Siting of Line Heat Detectors: Section 21.5 of the document provides specific recommendations for the siting of line heat detectors. These recommendations ensure that the detectors are placed in optimal locations to detect heat effectively and provide timely warnings.
Integration with Other Systems: The standard emphasises the importance of integrating linear heat detection systems with other fire protection systems. Compliance with relevant standards for the actuation of other fire protection systems is necessary to ensure a cohesive and effective fire safety strategy
Applications of Linear Heat Detection
Coated in different materials to suit specific applications, LHD cables are appropriate for use in the majority of dirty, dusty and hard to maintain environments – including damp, humid and unforgiving conditions. This is because they are unaffected by airflow, dangerous chemicals or toxins, removing the risk of reactive failure and false alarms – potentially leading to huge cost (and time) savings.
Examples include:
- Floating and fixed roof storage tanks
- Solar PV
- Car parks
- Cable trays
- Escalators
- Road and Access Tunnels
- Cold storage
- Warehouse racking
- Conveyor belts
- Control panels
- Hazardous and industrial environments
You can find out more here: Sectors – Thermocable
Detailed Guidelines for Linear Heat
Siting of Detectors:
- Flat Ceilings: The maximum distance between any point and the nearest detector should be 7.5 meters for smoke detectors and 5.3 meters for heat detectors
- Pitched Ceilings: The distance can be increased by 1% per degree of slope, up to 25% .
- Apex Roofs: Detectors should be within the top 600mm for smoke detectors and 150mm for heat detectors
- Voids: Detectors in unventilated voids should be within the top 10% or 125mm. Voids greater than 1.5 meters should be treated as rooms
- Obstructions: Detectors should not be within 500mm of walls or obstructions greater than 250mm
Line Heat Detectors:
- Horizontal Distance: Should not exceed 5.3 meters
- Pitched Ceilings: Distance can be increased by 1% per degree of slope, up to 25%
- Apex Roofs: Detectors should be within the top 150mm
- Voids: Same siting as other detectors, within the top 10% or 125mm
- Obstructions: Similar guidelines as other detectors
Other Considerations:
- Perforated Ceilings: Detectors above perforated ceilings should meet specific criteria, such as 40% perforation and a minimum dimension of 10mm
- Clear Space: Maintain a 500mm clear space below detectors Catching up with our technical expert, Commercial Manager, Harry Buck, he stated:
“The inclusion of linear heat detection standards EN 54-22 and EN 54-28 is a welcome step that formally recognises the technology as a practical and compliant option for fire detection in complex environments.”
Conclusion
The BS 5839-1:2025 standard provides detailed and specific guidelines for the design, installation, and maintenance of fire detection and alarm systems, with a particular focus on linear heat detection or line-type heat detection.
By adhering to these guidelines, building owners and managers can ensure that their fire detection systems are effective, reliable, and compliant with the latest safety standards.
We know this is a lot of information, but if you have specific questions or enquiries, you can get in touch with Harry here: [email protected]
Flat Ceilings: The maximum distance between any point and the nearest detector should be 7.5 meters for smoke detectors and 5.3 meters for heat detectors
Apex Roofs: Detectors should be within the top 600mm for smoke detectors and 150mm for heat detectors
Obstructions: Detectors should not be within 500mm of walls or obstructions greater than 250mm
