Fire detection without cladding

Fire detection without cladding

After considerable research and development Metalline, a fabricator of specialist architectural metalwork in the UK, has created a fire detection system that could be retrofitted into existing cladding with the intention of giving a faster reaction time than waking watch. The fire detection system is designed to monitor the façade using three different sensors on the cladding system – a smoke sensor in the cavity, a heat sensor in the cavity, and a heat sensor on the outside.

To investigate the response time of these sensors, Metalline approached the FPA to design and carry out a bespoke fire test to assess the performance of the system, examine how best to monitor the system and the spread of smoke, and establish how to insert the sensor into the cladding system without compromising the integrity of the system.

The testing was carried out on a specially constructed 10m wide and 9m high test rig at the FPA’s facilities to assess the detector response times across two 4.5m storeys, with detectors located at the edge of cavities. The worst-case scenario for a fire is with the most combustible cladding. However, the worst-case scenario for fire detector response time is with the least combustible cladding. Therefore, the majority of the test rig was constructed with non-combustible aluminium with mineral wool insulation.

5 ACM panels were used in the bottom left-hand corner of the test rig to serve as the main fuel source to assess the detector response times. Two types of sensors were installed in each test location: a heat detector and a smoke detector, with the majority installed to detect inside the cavity between the aluminium and the mineral wool, positioned on the internal face of the cladding.

An additional sensor was positioned externally above the fire and an A2-rated fire-protected sealant was used to seal the holes made to place the sensors.

Two tests were conducted on the test rig, with a fire positioned in one corner to assess the fire detector response times. The sensor activation times were measured relative to when the fire broke through the cavity. The test as designed defined cavity breakthrough as when either of the cavity thermocouples read 200°C above the ambient temperature for over 30 seconds.

The smoke detectors simulating a 10m wide cavity activated before the fire the broke into the cavity, whilst the smoke detectors simulating a 20m wide cavity activated within 1 minute and 5 seconds of fire breaking into the cavity. The heat detectors simulating a 10m wide cavity activated within 2 minutes and 21 seconds of fire breaking into the cavity.

The heat detectors simulating a 20m wide cavity did not all activate before the test was terminated, 15 minutes after the fire was ignited. However, the first detector located on the upper floor activated within 1 minute and 50 seconds of fire breaking into the cavity for both tests. The external heat detector reacted more slowly than the corresponding internal heat detector during both tests, despite being closer to the fire.

Ryan Brough, Head of Operations at Intelliclad said: “The test results proved the reliability of our application and allowed us to go on and win two national awards: Innovation of the Year at the National Building and Construction Awards 2022, and Smart Technology of the Year at the London Construction Awards 2022.”