5.1 Commentary

5.1.1 Introduction:

BS 5839 part 1 outlines the objectives and categories for fire detection and fire alarm systems in buildings. The main objectives are the protection of life and protection of property, which can vary depending on time and place. Additional objectives may include protection against business interruption and safeguarding the environment, typically addressed by complying with standards for property protection.

To accommodate different applications, BS 5839 categorizes systems into several Categories, as detailed in sections 5.1.2, 5.1.3, and 5.1.4. These categories ensure that fire detection and alarm systems are tailored to meet specific needs and risks associated with different types of buildings and environments.

5.1.2 Category M systems:

Category M systems are manual systems and, therefore, incorporate no automatic fire detectors.

5.1.3 Category L systems:

1. Category L1:

Installed throughout all areas of the building.
Objective: Provide the earliest possible warning of fire to maximize escape time for all occupants.

2. Category L2:

Installed in defined parts of the building, typically areas with high fire hazard or risk.
Objective: Provide early warning of fire in specified high-risk areas and achieve the same objectives as Category L3.

3. Category L3:

Designed to give early warning of fire to enable safe evacuation for all occupants, except possibly those in the room where the fire starts.
Detectors are typically installed in rooms opening onto escape routes.

4. Category L4:

Installed within escape routes such as corridors and stairways.
Objective: Warn occupants of smoke within escape routes to enhance their safety during evacuation.
Additional detectors may be installed beyond designated areas, still classifying the system as Category L4.

5. Category L5:

Tailored systems designed to meet specific fire safety objectives not covered by Categories L1 to L4.
Can range from localized detection for specific risk areas to comprehensive coverage in buildings with deviations from normal fire safety standards.
May or may not incorporate protection provided by Categories L2, L3, or L4 systems.

These categories ensure that fire detection and alarm systems are appropriately designed and installed based on the specific risks and safety objectives of different areas within buildings.

5.1.4 Category P systems

1. Category P1:

Installed throughout all areas of the building.
Objective: Provide the earliest possible warning of fire to minimize the time between ignition and the arrival of firefighters.
Aimed at protecting property by alerting authorities promptly to mitigate fire damage.

2. Category P2:

Installed in defined parts of the building, which can range from individual rooms to entire floors.
Objective: Provide early warning of fire in areas with high fire hazard levels or where the risk to property or business continuity from fire is significant.
Focuses on protecting specific areas or zones within the building where fire risk is identified as high.

These categories ensure that fire detection and alarm systems for property protection are strategically placed to detect and notify about fires promptly, thereby reducing potential damage and loss.

5.1.5 Selection of category

In buildings with comprehensive fire detection systems, manual call points are crucial for immediate fire activation. Systems designed for multiple purposes must meet the requirements of each category; for instance, a Category P1 system for property protection may not need alarms to wake sleeping occupants, unlike a Category L system for life safety. BS 5839 offers categories as flexible options, not mandates, allowing stakeholders to choose based on building needs, with Annex A providing guidance. Specifiers must clearly state the chosen category to ensure system alignment with safety goals, detailing protected areas except for Category L1, M, or P1. Differences between system categories like P1 and P2 are minimal, emphasizing selection based on specific safety objectives.

5.2 Recommendations:

Here are the key recommendations from BS 5839 regarding fire detection and alarm systems:

1. Statutory Requirements and Insurer Requirements:

Enforcing authorities and property insurers should clearly specify the category of fire detection and alarm system required.

2. Purchaser's Responsibility:

The purchaser or their representative must inform the system designer about the required category of system, clearly stating this in purchase or tender specifications.

3. Designer's Responsibility:

If the designer is not initially informed of the system category, they should clarify and propose a suitable category to the purchaser or their agent before proceeding with the system order.

4. Detailed System Description:

The system description should include sufficient information about the areas of the building that require protection, except for Category L1 or P1 systems where such details may be unnecessary.

5. Integration with Category M Systems:

Category L1, L2, L3, and L4 systems should also comply with the recommendations for a Category M system.

6. Combined System Description:

Systems that combine Category M requirements with Category P1, P2, or L5 requirements should be described accordingly (e.g., Category P1/M, P2/M, or L5/M).

7. Multiple Objective Systems:

Systems designed to satisfy the objectives of more than one category should be described using a combined notation (e.g., L2/P2 or L3/P2).

8. System Design Certificate:

The system design certificate should clearly state the designated category of system and provide a brief description of the areas protected by automatic fire detection, except for Category M, L1, or P1 systems where additional details may not be required.

5 Categories of system