A Closer Look at Some Assembly Occupancy Requirements
The fire at a Thai nightclub in early August 2022 was all too familiar. It started during a live music performance killing 20 people and injuring 25. Many of the details emerging are eerily similar to The Station nightclub fire which claimed the lives of 100 people and injured 230 more in February of 2003. In both instances, flammable interior finish and blocked exits were believed to have played a role in the fast-spreading fires and high number of fatalities. The 2003 tragedy led to a number of changes to NFPA 101, Life Safety Code, while also reiterating the importance of interior finish and means of egress requirements for assembly occupancies.
Interior finishes are the interior surfaces of a building that are generally secured in place like wall and ceiling coverings. They have proven to be a contributing factor in how quickly a fire spreads. To minimize the impact interior finish has on fire spread, Chapter 10 of the 2021 edition NFPA 101, Life Safety Code®, establishes basic requirements for interior wall, ceiling, and floor finishes. Chapter 10 outlines two testing options: 1) testing in accordance with NFPA 286, Standard Methods of Fire Tests for Evaluating Contribution of Wall and Ceiling Interior Finish to Room Fire Growth; or 2) testing in accordance with ASTM E84 or UL 723. Paragraph 10.2.3.1.2 of the 2021 edition of NFPA 101, outlines acceptance criteria for materials tested in accordance with NFPA 286. The acceptance criteria includes: limitations on the spread of flames; peak heat release rate less than 800 kW; and for new installations the total smoke released throughout the test cannot exceed 1000 m2. Any material that meets the criteria outlined in 10.2.3.1.2 can be used wherever a Class A material is permitted. The alternative test method (ASTM E84 or UL 723) results in the material being grouped into a class. There are three classes- Class A, Class B, and Class C which are determined by a material’s flame spread index and smoke developed index. Class A materials will have the lowest flame spread index of the three classifications. The smoke developed index is the same range for all three classifications. For newly installed materials both the flame spread index and smoke developed index is considered, whereas for existing materials only flame spread index is considered. Occupancy chapters may further regulate interior finish beyond what is contained in Chapter 10. In both fires, acoustic material is believed to have been a major contributing factor in the rapid spread of fire. Assembly occupancies do further regulate interior finish. The requirements are the same for new and existing assembly occupancies. In general assembly areas with an occupant load of 300 or fewer, ceiling and wall materials must be Class A, B, or C. In general assembly areas with an occupant load of more than 300, and in corridors, and lobbies, interior wall and ceiling finishes must be Class A or B. In enclosed stairs interior finish materials must be Class A.
One other contributing factor was the availability of exits. In both the fire in Thailand and at The Station nightclub, one of the doors to the outside was blocked for use by occupants to allow the band performing to have their own separate entrance/exit. One of the fundamental components of the Life Safety Code is the concept of free egress. Prohibiting people from entering the building via a door is one thing, but not allowing occupants to exit the building via the nearest door is unacceptable. Additionally, NFPA 101 prohibits the means of egress for assembly occupancies from going through hazardous areas such as kitchens, storerooms, closets, stages, and platforms. There are also requirements related to the size of a main entrance/exit, where one exists. History has shown that occupants tend to go out the way they came, even if there is an exit closer. The main entrance/exit provisions are intended to prevent crowd crush situations. In existing assembly occupancies, the main entrance/exit needs to be sized to accommodate at least one-half the total occupant load. For new assembly occupancies that are dance halls, discotheques, nightclubs, or that have festival seating, the main entrance/exits must be wide enough to accommodate two-thirds of the total occupant load. The main entrance/exit for all other new assembly occupancies must be sized to accommodate one-half the total occupant load. If the assembly occupancy is more than one level, then each level must have access to the main entrance/exit and that access must be sized to handle two-thirds (for new assembly occupancies) or one-half (for existing) of the occupant load of that level. The main entrance/exit requirements for certain types of new assembly occupancies was increased from one-half to two-thirds the total occupant load due to a crowd crush event during The Station nightclub fire.
Another way the Life Safety Code strives to reduce the risk of crowd crush is by requiring trained crowd managers. All assembly occupancies, with the exception of certain ones used exclusively for religious worship, are required to have at least one trained crowd manager. Depending on the total occupant load, additional crowd managers may be required. Typically, there should be one crowd manager for every 250 occupants. Prior to the 2006 Edition, crowd managers were only required for assembly occupancies with occupant loads of more than 1000. After The Station nightclub fire, the Life Safety Code was changed to require at least one crowd manager for all assembly occupancies. Within 2 minutes of the fire starting at The Station nightclub, there was crowd crush at the main entrance/exit. This led to the main entrance/exit being almost completely impassable. The crowd manager’s responsibilities include understanding crowd management, understanding methods of evacuation, being familiar with the facility evacuation plan, being familiar with the emergency response procedures, and understanding procedures for reporting emergencies.
While the cause of the recent fire at the Thai nightclub is still under investigation, The Station nightclub fire was caused by pyrotechnics. To reduce the risk of open flames or pyrotechnics starting a fire in an assembly occupancy they are prohibited unless certain conditions are met. In order for pyrotechnics to be used on stage before proximate audiences, precautions to prevent ignition of any combustible material, satisfactory to the authority having jurisdiction must be met and the use of the pyrotechnic device must comply with NFPA 1126, Standard for the Use of Pyrotechnics Before a Proximate Audience.
As we have seen countless times, fires in assembly occupancies, and in particular nightclubs, can result in a high number of fatalities. By carefully considering the use of open flames and pyrotechnics we can eliminate potential ignition sources in these types of occupancies. Additionally, ensuring the interior finish requirements for assembly occupancies are met can help slow the spread of fire. Fires in an assembly occupancy have the added risk of leading to a crowd crush event. Compliance with the means of egress and crowd manager requirements will help reduce the risk of crowd crush events during emergency situations.