How to Design Fire Evacuation Linkage: Broadcasting Evacuation, Audio-Visual Alarms, and Access Control Unlock for Escape Routes

What Is Fire Evacuation Linkage?

Fire evacuation linkage is an integrated control mechanism in which a Fire Alarm System (FAS) detects a fire and sends coordinated commands to subsystems including access control, fire broadcasting, audio-visual alarms, and video surveillance. Each subsystem operates according to predefined logic, guiding occupants to safety exits, removing barriers from evacuation paths, ensuring visual and audible direction, and providing real-time situational awareness. The core objective is to eliminate obstacles within the critical evacuation window and maintain continuous monitoring of evacuation conditions.

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1. Triggering Logic and Priority Design for Four Subsystem Categories

1.1 Priority Architecture

Fire evacuation linkage does not activate all subsystems simultaneously. A clear response sequence must be established based on the urgency of life-safety protection. The commonly adopted priority framework is as follows:

> Note: The response times above are industry experience reference values. Actual project requirements should be confirmed against the design institute's detailed system drawings and local fire authority review comments.

1.2 Trigger Signal Sources

Trigger signals typically originate from the following fire alarm devices:

• Fire Alarm Control Panel (FACP): Serves as the central hub for linkage logic, outputting standard protocol signals (such as RS485, CAN, or IP-based protocols).
• Intelligent smoke/heat detectors: In analog addressable systems, detector alarm address codes correspond to specific zones, and linkage logic is configured by zone.
• Manual fire alarm call points: Personnel manually confirm fire conditions before triggering linkage, preventing false activations caused by a single detector malfunction.

1.3 Subsystem Triggering Logic in Detail

(1) Access Control Unlock Linkage

Trigger condition: FACP sends a fire zone linkage signal; the access control server receives and parses the alarm address code.

Execution logic:

1. The access control server issues an "unlock" command to all access controllers within the fire zone.
2. For electromagnetic locks (fail-secure type), power loss releases the lock. For electric strikes, an explicit unlock signal must be sent.
3. Access doors to stairwell vestibules typically remain in a "power-off closed" state (manual push-through is unaffected during evacuation), and are only unlocked via linkage when the confirmed fire zone has direct connectivity risk to the stairwell.
4. Elevator lobby access control forces release in fire mode to prevent occupants from entering elevators.

Key parameter verification:

• Access controllers must support dry-contact signal input or standard fire alarm protocol integration (such as Modbus or ONVIF Event).
• Electromagnetic lock holding force is recommended to be ≥ 600 N (subject to actual project) to ensure door panels remain stable under non-forced conditions.
• Access control servers should support offline independent operation; even if the upper-level platform fails, the FACP's hardwire linkage signal can still directly drive lock release.

(2) Fire Broadcasting Linkage

Trigger condition: FACP activates the linkage module, triggering the zone controller of the fire broadcasting system.

Execution logic:

1. Broadcasting in the fire zone switches automatically, prioritizing pre-recorded evacuation messages (such as "Please note: a fire has been detected in your area. Please evacuate orderly through the emergency exits").
2. Manual broadcasting takes priority over automated voice. Fire control room operators can use microphones for real-time command.
3. Background music in non-fire zones automatically reduces volume to ensure evacuation instructions remain clearly audible.
4. Broadcasting zones should align with fire alarm zones or be integer multiples thereof, enabling precise command.

Selection criteria:

• Power amplifier capacity is configured at 1.3–1.5 times the total speaker power of the coverage area (subject to actual project).
• Speaker sensitivity is recommended to be ≥ 90 dB (subject to actual project), ensuring clear voice intelligibility under ambient noise conditions of 85 dB.
• Amplifiers must feature automatic main/backup switching with a switching time ≤ 0.5 seconds.

(3) Audio-Visual Alarm Linkage

Trigger condition: FACP outputs DC power or relay signals to the audio-visual alarm circuit.

Execution logic:

1. The fire alarm control panel energizes the audio-visual alarm circuit for the corresponding zone.
2. Audio-visual alarms simultaneously emit audible alerts (≥ 75 dB, subject to actual project) and strobe light signals.
3. Audio-visual alarms are typically installed per fire compartment or smoke compartment, with at least one unit per zone.
4. Required installation locations include corridors, stairwell vestibules, and elevator lobbies.

Placement principles:

• Installation height is recommended at 2.0–2.5 m (subject to actual project), ensuring placement above eye level.
• Spacing between adjacent audio-visual alarms is recommended to be ≤ 15 m (subject to actual project).
• Underground spaces and humid environments require equipment with ingress protection rating ≥ IP65.

(4) Route Monitoring Linkage

Trigger condition: FACP pushes alarm events to the video management platform via hardwire or network connection.

Execution logic:

1. The video management platform receives fire alarm events and parses camera IDs corresponding to alarm locations.
2. Cameras automatically call preset positions, and video feeds switch to monitoring displays or operator clients.
3. Video recording triggers full-duration capture, with storage duration recommended ≥ 24 hours (subject to actual project).
4. Intelligent analytics (such as crowd density detection and abnormal loitering alerts) may serve as auxiliary tools but are not used as fire confirmation criteria.

Placement requirements:

• At least one camera should cover each stair landing in evacuation stairwells.
• For straight evacuation corridor sections, camera spacing is recommended ≤ 30 m (subject to actual project).
• Key placement locations include fire vestibules, elevator lobbies, and equipment room entrances.
• Camera selection is recommended to use low-light network cameras with resolution of 1080p or higher.

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2. Evacuation Route Monitoring Camera Placement Methodology

2.1 Tiered Placement Model

Based on security-fire integration project experience, evacuation route monitoring can be executed using a three-tier placement strategy:

Tier 1 (Core evacuation routes): Stairwells, stair vestibules, and safe exit lobbies—installed on every floor, prioritizing explosion-proof or high-protection-grade cameras.

Tier 2 (Secondary evacuation routes): Long corridors (> 30 m requiring additional cameras), refuge corridors, and equipment room evacuation doors—configured based on corridor length and occupant density.

Tier 3 (Peripheral control): Fire engine access roads, fire control room entrances, and emergency generator rooms—supporting emergency command, not directly involved in evacuation guidance.

2.2 Viewing Distance and Focal Length Calculation

Camera focal length selection must be determined based on monitoring distance and coverage width:

> Note: The parameters above are experience-based references assuming a 1/2.8" sensor format. Actual selection should be confirmed against the equipment manufacturer's technical specifications.

2.3 Storage Capacity Estimation

Video storage capacity can be estimated using the following formula:

Daily storage (TB) = Number of cameras × Bitrate per camera (Mbps) ÷ 8 × 3,600 × Daily runtime (h) ÷ 1,024

• Typical 1080p bitrate: 4–6 Mbps (subject to actual project)
• Typical 4MP bitrate: 6–8 Mbps (subject to actual project)
• Storage retention period is recommended ≥ 30 days (subject to actual project); critical areas may extend to 90 days

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3. Linkage Sequence and System Integration Design

3.1 Standard Linkage Sequence

The typical action sequence of the four subsystems on a timeline is as follows (to be confirmed against design institute detailed drawings and local fire authority requirements):

3.2 False Alarm Suppression Mechanisms

To prevent a single detector false alarm from triggering large-scale linkage, the following configurations are recommended:

• Multi-condition confirmation: Linkage triggers after both smoke and heat detectors confirm, or after smoke detector alarm persists for ≥ 30 seconds (subject to actual project).
• Phased linkage: Phase 1 activates only audio-visual alarms; Phase 2 (triggered by manual confirmation or dual-detector confirmation) unlocks access control and activates broadcasting.
• Dual hardware/software redundancy: FACP hardwire linkage operates in parallel with platform software linkage, ensuring a backup path remains functional if either channel fails.

3.3 System Integration Methods

The three primary methods for integrating each subsystem with the fire alarm system are:

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4. Practical Recommendations: Key Checklist for Project Implementation

4.1 Design Phase

• [ ] Confirm local fire authority requirements for evacuation linkage response times (subject to official release)
• [ ] Align with the design institute on the correspondence between fire alarm zones and access control/broadcasting/monitoring system zones
• [ ] Catalog lock types (electromagnetic lock/electric strike/anode lock) and confirm default state in fire mode
• [ ] Verify fire broadcasting power amplifier capacity against speaker distribution density
• [ ] Establish false alarm suppression strategy; define single-detector vs. multi-detector confirmation logic

4.2 Equipment Selection Phase

• [ ] Access controllers: Support standard fire alarm protocols or have dry-contact linkage interfaces
• [ ] Fire broadcasting amplifiers: Automatic main/backup switching with switching time ≤ 0.5 seconds
• [ ] Audio-visual alarms: Ingress protection ≥ IP65 (outdoor/humid environments), sound pressure level ≥ 75 dB
• [ ] Cameras: Low-light capability, 1080p or higher resolution, support ONVIF protocol and standard alarm event input
• [ ] Video management platform: Support alarm-triggered video wall switching, preset recall, and recording activation

4.3 Commissioning Phase

• [ ] Zone linkage testing: Trigger each fire zone individually; verify complete chain of access unlock, broadcasting, audio-visual activation, and video switching
• [ ] False alarm testing: Simulate single-detector alarm; verify linkage logic complies with phased suppression design
• [ ] Network failure testing: Simulate network interruption; verify hardwire linkage path functions independently
• [ ] Manual reset testing: After fire incident resolution, verify system reset procedures for all subsystems
• [ ] Document test reports as fire acceptance documentation

4.4 Operations and Maintenance Phase

• [ ] Establish quarterly linkage testing to ensure system availability
• [ ] Access control locks: Recommend holding force testing every six months (subject to actual project)
• [ ] Broadcasting system: Recommend voice intelligibility testing every quarter
• [ ] Video storage capacity: Conduct periodic inspection to ensure storage retention requirements are met

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FAQ

Q1: What are common reasons why access control fails to unlock during a fire?

Common causes include: access controller not connected to fire alarm linkage signal, FACP output module failure, lock power supply circuit disconnection, or the zone not configured with linkage logic in the access control software. Recommended first step: verify hardwire circuit continuity, then review software configuration parameters.

Q2: Can fire broadcasting and background music systems share the same amplifier?

Technically feasible, but reliable priority switching during fires must be ensured. Independent amplifiers or amplifiers with dual-input automatic switching are recommended. Background music systems should not compromise the reliable operation of fire broadcasting.

Q3: Can wireless cameras be used for evacuation route monitoring?

In fire scenarios, wireless link reliability presents risks. Wired networks (PoE or independent power supply) are recommended as the primary approach. If wireless is necessary due to site constraints, additional wireless link monitoring and automatic alerting mechanisms should be configured.

Q4: Can video analytics replace traditional detectors as fire confirmation criteria?

No. Video smoke detection or thermal imaging can serve as supplementary detection methods, but fire confirmation should still rely on smoke and heat detectors that meet fire certification standards. Video analytics is better suited for evacuation situational awareness monitoring and post-incident evidence.

Q5: What documentation is required for linkage system acceptance?

Standard acceptance documentation typically includes: linkage logic configuration tables, test reports (including zone-by-zone test records), equipment inventory (with fire certification certificates), system topology diagrams, and operation and maintenance manuals. Specific requirements should be confirmed against local fire authority regulations.

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Conclusion

The core of fire evacuation linkage design lies in establishing clear priorities, configuring reliable triggering logic, ensuring robust subsystem integration, and fully addressing false alarm suppression and network-failure contingency scenarios during the design phase. Access control unlock ensures evacuation paths remain clear; fire broadcasting provides voice guidance; audio-visual alarms reinforce visual and audible warnings; and route monitoring supports situational awareness—only through coordinated operation of all four elements can a complete emergency evacuation system be established. During project implementation, close coordination with the design institute is recommended. Linkage parameters and timing configurations should be confirmed against detailed drawings and local fire codes, and phased commissioning combined with regular testing should be conducted to ensure ongoing availability.