Fighting Fires and Saving Lives in Large, Single-Story, Undivided Buildings

A closer look at the need to incorporate automatic smoke vents into these designs
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Sponsored by The BILCO Company
By Jeanette Fitzgerald Pitts
910.2.1 Group F-1 or S-1

Smoke and heat vents installed in accordance with Section 910.3 or a mechanical smoke-removal system installed in accordance with Section 910.4 shall be installed in buildings and portions thereof used as Group F-1 or S-1 occupancy having more than 50,000 square feet of undivided area. In occupied portions of a building equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 where the upper surface of the story is not a roof assembly, a mechanical smoke removal system shall be installed. Exception: Group S-1 aircraft repair hangars.

910.2.2 High-Piled Combustible Storage

Smoke and heat removal required by Table 3206.2 of the International Fire Code (IFC) for buildings and portions thereof containing high-piled combustible storage shall be installed in accordance with section 910.3 in unsprinklered buildings. In buildings and portions thereof containing high-piled combustible storage equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, a smoke- and heat-removal system shall be installed in accordance with Section 910.3 or 910.4. In occupied portions of a building equipped throughout with an automatic sprinkler system in accordance with an automatic sprinkler system in accordance with Section 903.3.1.1, where the upper surface of the story is not a roof assembly, a mechanical smoke removal system in accordance with Section 910.4 shall be installed.

In summary, the 2018 IBC requires the installation of smoke and heat vents in factories, industrial buildings, and storage facilities that have more than 50,000 square feet of undivided area and where the upper surface of the story is a roof assembly. Table 3206.2 of the IFC (referenced in the code language above) requires smoke and heat removal in high-piled storage areas holding commodity classes I-IV that are greater than 12,000 square feet or considered nonpublic accessible and between 2,501 and 12,000 square feet in size. High-piled storage areas containing commodities deemed High Hazard must have a system for smoke and heat removal if the area is larger than 2,501 square feet or identified as nonpublic accessible and between 501 and 2,500 square feet. The IBC and IFC also contain provisions that state the minimum ratio of area of vents provided to the floor area and the maximum spacing of vents.

UL 793 Standard for Automatically Operated Roof Vents for Smoke and Heat

In addition to standards that dictate where automatic roof vents must be included and the standards that guide designers in creating systems that meet certain performance objectives, there are standards that provide construction and performance criteria that the manufacturers of automatic smoke vents must meet. Underwriters Laboratories (UL) develops standards that help companies demonstrate safety, confirm compliance, and deliver quality in a wide array of product types. The UL 793 Standard for Automatically Operated Roof Vents for Smoke and Heat defines certain requirements for automatically operated roof vents in both the mechanically opened and gravity-opened categories.

Photo courtesy of The BILCO Company

Acoustical smoke vents are designed to guard against noise intrusion and are ideal for concert halls, theaters, and other interior applications that require limited noise from the outside.

As stated in the scope of UL 793 Standard, “The vents covered by these requirements are operated manually or automatically in the event of fire to remove smoke and heat from the building. Automatic operation does not depend upon electrical power or other energy sources that may be interrupted during a fire, but rather on operation of a heat-responsive device or on the action of a plastic cover shrinking and falling from place due to fire exposure or the like. These vents are not intended for use as general-purpose building ventilation devices.” The UL standard contains requirements for vent construction, performance, marking, and installation and operating instructions.

The Benefits of Automatic Smoke Vents

Designing large, single-story, undivided industrial, manufacturing, and storage facilities to meet codes and effectively manage a fire, protecting people and property inside, is an especially important topic today, as the online shopping trend has resulted in a proliferation of large warehouse spaces across the nation. But automatic smoke vents also offer incredible life-saving benefits to other large, undivided venues where the upper surface of the main story is the roof, such as convention centers, arenas, stadiums, performance theaters, and auditoriums.

Photo courtesy of The BILCO Company

By allowing the heat, smoke, and gases to escape a burning building, automatic smoke vents allow an increased evacuation time, decrease the risk of smoke inhalation, enhance visibility for firefighters, and protect the structure from damaging heat.

Increased Evacuation Time and Decreased Risk of Smoke Inhalation

By removing smoke, heat, and gases from a burning building, automatic smoke vents can offer people in the building more time to safely exit the premises and decrease the risk of smoke inhalation, which is recognized as the number one cause of death related to fires.

Enhanced Visibility for Firefighters

Providing smoke, hot gases, and products of combustion with a path to exit the building, instead of trapping them inside, also improves the visibility that firefighters have of the interior once they arrive on the scene, and enables them to more quickly locate the fire and formulate a plan to contain it.

Release Noxious and Potentially Explosive Fumes

Fires also release dangerous gases into the air, including carbon monoxide, which is lethal, and fire smoke often contains a whole host of other toxic threats like hydrogen cyanide and inorganic acids. Exposure to these toxicants can be the principal cause of death found in victims of fires. During fires, potentially explosive fumes can also be released. Automatic smoke vents remove noxious and potentially explosive gases from the area, making the burning environment safer for people and firefighters to travel through it.

Protects Against Secondary Ignitions and Lateral Fire Spread

Intense heat is one of the components that can cause a secondary ignition in a fire, which causes the fire to move through a building laterally away from the initial area of combustion. Automatic smoke vents allow the heat and smoke to escape the building, eliminating the potential for the problematic buildup of intense heat and helping to keep the fire from spreading from its original location.

Protect the Structure from Damaging Heat

When fires start, a smoke plume of hot gases and smoke rises directly above the area of combustion until it hits the ceiling. Unable to break through the ceiling, the hot gases remain trapped at the horizontal surface, getting thicker and hotter as the fire burns. Exposure to the intense heat in those gases can damage structural elements in the building. Automatic smoke vents slow the buildup of these hot gases at the ceiling and can even reverse it, protecting the structure from the damaging levels of heat that can be produced.

Reduced Damage to Buildings and Their Content

Smoke detectors and sprinkler systems are installed in the ceiling because smoke and hot gases produced by fires first rise to the ceiling before spreading horizontally across the surface and through the building. As previously discussed, this can cause sprinklers to activate that are not directly over a fire condition, which can result in unnecessary water damage to contents and property not directly involved in the fire. When automatic smoke vents closest to the actual zone of combustion open, they pull the hot gases and smoke out of the building so that they don’t travel further away from the fire and set off these additional sprinklers, which reduces the damage caused to the building and the contents inside.

Many architects and engineers, fire authorities, and insurance carriers agree that specifying automatic vents for modern industrial and commercial structures offers a significant benefit and dramatically improved outcomes in the protection of lives and property. The first step is learning how to select the right automatic smoke vent for a specific project.

 

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Originally published in Architectural Record

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