THE EVOLUTION OF FIRE SAFETY FOR MULTI-STORY STRUCTURES
Back in 1974, the disaster movie called The Towering Inferno was about a fire breaking out in a fictional highrise. Unfortunately, Hollywood became reality over the next few years, when several notable multi-story building fires occurred. But the MGM Grand Hotel fire that killed 85 and injured 679 in 1980 prompted the state of Nevada and other governments to institute major fire safety guideline and code reforms. This event was one of the main contributors to the birth of today’s firestop industry because regulators and industry groups began working together to develop firestop requirements in commercial building codes. Today, their joint efforts to improve safety in larger structures continues.
Disasters Lead to Protection Requirement Updates
Distributed Antenna System (DAS)
During the 9/11 attacks in 2001, first responders quickly lost radio signals and couldn’t communicate with each other. As a result, updates to the International Fire Code now say radio coverage for new buildings should match the level of existing coverage at the exterior of the building (IFC 510 and IFC 907). One way to achieve this is with a Distributed Antenna System (DAS) – a network of smaller antennas with signal boosters. They can provide the same coverage as a single larger antenna, but connecting backbone cables are required to be protected to remain functional during a fire.
Critical Power Systems
Certain power circuits are also considered critical and require fire-resistance ratings. For high rises, the 2018 International Building Code (IBC) includes these power systems as critical electrical circuits:
- Smoke control systems
- Fire pumps
- Emergency and standby power systems
- Fire service access elevators
- Occupant evacuation elevators
Until 2015, the IBC allowed only fire-resistive cables tested to UL 2196 for these critical electrical circuits and required a fire-resistance rating of not less than one or two hours, depending on specific application. The 2018 IBC includes that standard but adds an option:
… electrical circuit protective systems meeting either UL 1724 or ASTM E1725 with a fire resistance rating of not less than one or two hours, depending on application. -2018 IBC
So, now there’s a choice to use either fire-resistive cable or conventional cable in a fire-resistive envelope.
While ceramic insulation or blankets may have specific applications for creating a fire-resistive envelope around these critical circuit installations, they can also interfere with heat dissipation – and that will de-rate the ampacity of the cables. Some form of endothermic wrap may be a better solution since it allows for more heat dissipation than other typical enclosures. These wraps have chemically bound water which is released at high temperatures during a fire. The water absorbs heat, and that slows heat flow to the protected area for a time. More layers can be used to adjust the fire-resistive duration.
There’s Always More That Can Be Done
The firestop industry has come a long way since the 1980s, with vast upgrades to both high-rise regulations and technologies. But we all know there is still room for improvement. Together, we can keep finding new ways to improve by working with the rest of the industry.
Reprinted by permission:
Mark W. Lund, P.E., M.Sc.
3M Senior Supervisor, Application Engineering
3M Senior Application Engineer