At 2 a.m. August 7th 2021, the emergency response centre of the city of Bergen, Norway, received a call from a private citizen reporting large flames appearing from a 4 floor 24 apartment municipal building housing people with drug addiction. Upon arrival 11 min later, the first responders faced a fire that had already spread and involved the whole building. To their surprise, all residents were already accounted for outside the building. The present study analyses why the fire developed that fast, why the automatic fire alarm system did not warn the emergency response centre early and how all occupants were accounted for in such a dramatic fire scenario. It turns out that the fire most likely started in one of the all-wooden floor balconies at ground level. The originally planned 1.2 m tall balcony glazing facing a public road had been substituted by wood to ensure privacy and prevent visibility. The balcony subdivision walls had 20 cm gaps at ceiling level. Analysis confirmed that this balcony construction, i.e., all-wooden and with gaps at the top of the division wall, contributed significantly both during the early fire development as well as to the very fast vertical and horizontal fire spread over the entire building façade. Post-fire interviews revealed that a significant number of occupants were awake this night, allowing them to promptly detect the fire in the building. A close-knit relationship network, including both friends and acquaintances, was of major importance regarding door-to-door alarming unaware residents about the immediate danger. From the investigations conducted after the fire it is quite clear that under different circumstances this fire could have resulted in multiple fatalities. Though the incident may be considered a success regarding the "no loss of lives" focus in Norwegian fire safety regulations, the study revealed weaknesses in balcony construction and use of materials as well as lack of exterior automatic fire detection and mitigation of external fires. The study revealed important learning points for future prevention of possibly far worse fire incidents , as well as the importance of a close-knit relationship network in a crisis situation.

Cross-laminated timber (CLT) is becoming increasingly popular due to its many advantages. However, it has been shown that exposed CLT can have a significant effect on fire dynamics and spread rates. Further studies are therefore needed to better understand the impact of CLT to fire safety. Two large-scale CLT compartment fire experiments (95 m2) representing a modern office building have been performed, #FRIC-01 and #FRIC-02. This paper presents the second experiment, #FRIC-02, with exposed CLT on the back wall and the ceiling. The fire developed fast and spread across the room in less than 3.5 min from ignition of the wood crib on the floor and in 1.5 min after the ignition of the ceiling. Large external flames were observed, despite the compartment being well-ventilated. The 5-layer CLT, which comprised a 40 mm thick exposed outer layer and was face-bonded using a common European polyurethane adhesive, exhibited glue-line integrity failure and led to a second flashover after a significant period of decay. Subsequent layers of 20 mm also delaminated before the fire was manually extinguished after 3 h. Compared to #FRIC-01, the fire spread rate was faster, and temperatures, charring rates, heat release rates and external flames were higher.

Cross-laminated timber (CLT) is becoming increasingly popular due to its many advantages. However, it has been shown that exposed CLT can have a significant effect on fire dynamics and spread rates. Further studies are therefore needed to better understand the impact of CLT to fire safety. Two large-scale CLT compartment fire experiments (95 m2) representing a modern office building have been performed, #FRIC-01 and #FRIC-02. This paper presents the second experiment, #FRIC-02, with exposed CLT on the back wall and the ceiling. The fire developed fast and spread across the room in less than 3.5 min from ignition of the wood crib on the floor and in 1.5 min after the ignition of the ceiling. Large external flames were observed, despite the compartment being well-ventilated. The 5-layer CLT, which comprised a 40 mm thick exposed outer layer and was face-bonded using a common European polyurethane adhesive, exhibited glue-line integrity failure and led to a second flashover after a significant period of decay. Subsequent layers of 20 mm also delaminated before the fire was manually extinguished after 3 h. Compared to #FRIC-01, the fire spread rate was faster, and temperatures, charring rates, heat release rates and external flames were higher.

On the night of 7th of August 2021, a fire occurred in a municipal residential building that was used as housing for substance abusers in Bergen, Norway. The fire was described as violent and with a rapid fire spread. However, all residents evacuated on their own, coming from the incident without physical injuries. It is unreasonable that such a fire development should be considered acceptable in Norway. An interdisciplinary project group in FRIC has investigated this fire with the aim of identifying key learning points that may be useful in the work to improve fire safety for similar buildings and users in the future. This may provide a basis for development of available tools for relevant authorities, e.g., means for communication and information and possible amendments of regulations. We have focused on the following two issues: 1. Why did the fire develop so quickly? 2. Why were there no injuries or fatalities in the fire? Consideration has also been given to what could have happened if important circumstances had been different, such as conditions related to the start of the fire and the alarm. Various methods were used to collect relevant information. An inspection of the fire site was carried out on 8th of September 2021 together with Bergen Fire Department and Vest Police District. Emergency responders from the police and fire departments were interviewed. Documentation from the building case, documents from the police investigation and the Bergen Fire Department's evaluation report of the incident have been reviewed, in addition to relevant literature on various topics. Fire properties of undamaged cladding material from the building were investigated by small scale fire testing (the cone calorimeter) in a master's thesis at NTNU that was associated with the project. .....................................Norwegian Description follows:............................ Natt til 7. august 2021 oppsto det en brann i et kommunalt boligbygg som ble anvendt som botrening for rusmisbrukere i Bergen. Brannen ble beskrevet som voldsom og med en rask brannspredning, men alle beboerne evakuerte på egen hånd, og kom fra hendelsen uten fysiske skader. Det er urimelig at en slik brannutvikling skal kunne anses som akseptabel i Norge. En tverrfaglig prosjektgruppe i FRIC har undersøkt denne brannen med en målsetting om å identifisere viktige læringspunkter som kan komme til nytte i arbeidet med å forbedre brannsikkerheten for tilsvarende bygninger og brukere i fremtiden. Dette kan gi grunnlag for å utvikle de virkemidlene som relevante myndigheter har til rådighet, for eksempel kommunikasjons- og informasjonstiltak, og utvikling av regelverk. Vi har fokusert på følgende to problemstillinger: 1. Hvorfor utviklet brannen seg så raskt? 2. Hvorfor var det ingen skadde eller omkomne i brannen? Det er også vurdert hva som kunne skjedd dersom viktige forhold hadde vært annerledes, eksempelvis forhold knyttet til brannstart og alarm. Det ble anvendt ulike metoder for å samle inn relevant informasjon. Det ble foretatt en befaring av branntomten 8. september, 2021 sammen med Bergen brannvesen og Vest politidistrikt. Innsatspersonell fra politi og brannvesen ble intervjuet. Dokumentasjon fra byggesak, dokumenter fra politiets etterforskning og Bergen brannvesens evalueringsrapport av hendelsen er gjennomgått, i tillegg til relevant faglitteratur innenfor ulike tema. Brannegenskaper til uskadet kledningsmateriale fra bygningen ble undersøkt ved brannteknisk prøving i liten skala (konkalorimeteret) i en masteroppgave ved NTNU som var tilknyttet prosjektet.