Sprinkler Protection and Vertical Openings

By John Swanson posted Mar 13, 2022 03:12 PM

  

On November 21, 1980, a fire at the MGM Grand Hotel and Casino in Las Vegas, Nevada took the lives of 85 people and injured over 650. At the time of the fire, 5,000 people were either in the casino or staying in one of the 2,000 hotel rooms. The fire began around 7:00am in one of the first-floor restaurants while most people were asleep in the hotel. The fire spread quickly throughout the 26-story partially sprinklered building. Today, the MGM Grand Fire remains the third deadliest hotel fire in United States history and had a significant impact on building and fire codes throughout the country. One of the most concerning statistics from this fire was, 61 of the 85 deaths (over 70%) were found on floors 19-24.

Why so many deaths on the upper floors?

Investigators needed to determine why a fire that started on the first-floor lead to so many deaths on the upper floors. The primary factor in the high number of deaths at the MGM Grand was due to unsealed vertical openings. When built, sprinklers were provided on the first two floors and the top floor of the hotel only, but the remaining floors of the hotel, casino area, and the deli (the origin of the fire), were exempted from sprinkles because they were open 24 hours. A determination was made that since the casino was open 24 hours, any fire would be quickly located and handled with fire extinguishers. However, at some point between opening and the date of the fire, the deli changed hours and was closed at the time of the fire. This allowed the fire to grow unchecked and spread to other areas of the building. Unfortunately, the MGM Grand incident was one of several fires in our nation’s history where vertical openings was a contributing factor in the loss of lives.

Vertical openings, closely spaced sprinklers, and draft curtains

Today, model building codes dedicate entire chapters to limiting the spread of smoke, fire, and products of combustion in a building. Typically, protection of vertical openings involves compartmentalizing areas with fire-resistive construction and/or installing an automatic sprinkler system to control or even extinguish a fire. The International Building Code (IBC) has two sections regulating the use of closely spaced sprinklers (sometimes referred to as a water curtain) and draft curtains as one method of protecting vertical openings: Section 712.1.3.1 regulating escalator openings and Section 1019.3 in relation to exit access stairways and ramps.

IBC Section 712.1.3.1 – Escalator Openings

Section 712.1.3 establishes the criteria for escalator (or vertical) openings in buildings. This section applies to all occupancies. Except for Business (Group B) and Mercantile (Group M) occupancies, the maximum number of stories allowed to be open for the escalator is four. The number of escalator floor openings is not limited for Groups B and M occupancies. For design professionals to use this section, the building must be protected throughout with NFPA 13 system, and the area around each escalator opening must be protected by a draft curtain and closely spaced sprinklers installed in accordance with Section 9.3.5 in the 2022 Edition of NFPA 13.

The IBC gives a second option for escalator openings (Section 712.1.3.2) where automatic shutters may be used around the floor opening. However, the use of closely spaced sprinklers and a draft curtain is often more advantageous and economical for the owner as an alternative to enclosing the vertical opening with fire rated construction. Factors taken into consideration include the overall cost of fire rated equipment/construction materials, inspection, testing and maintenance (ITM) requirements, and necessary repairs over the life of the building to ensure the fire rated equipment continues to operate as intended.

IBC Section 1019.3 – Exit Access Stairways and Ramps

The second option in the IBC for closely spaced sprinklers is found in Section 1019.3. This section regulates exit access stairways and ramps. Section 1019.3 requires the stair or ramp to be enclosed in a (fire rated) shaft enclosure. However, an exception allows the shaft enclosure to be eliminated when the building is protected throughout with an NFPA 13 sprinkler system and openings between stories are protected with closely spaced sprinklers and a draft curtain. Business and Mercantile occupancies are permitted to have a maximum of four stories open when applying the exit access stairway and ramp requirements. It’s important to clarify this section only applies to exit access stairways and ramps. Interior exit stairways and ramps will typically be enclosed within fire rated construction. Exit access stairways are not required to be enclosed in fire rated construction but are still subject to the vertical opening requirements in the IBC.

Clarification and Summary

There have been questions regarding when closely spaced sprinklers and a draft curtain must be provided. To clarify, it is not required any time there’s an opening from one story to another. The requirement for closely spaced sprinklers and a draft curtain applies when the occupancy exceeds the maximum number of floors allowed to be open. For most occupancies, additional protection is required when the vertical opening connects three or more stories. For example, a two-story office building (Group B) with an open exit access stairwell in the main lobby does not require closely spaced sprinklers and draft curtain because the IBC allows two stories to be open in Business occupancies.

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