Appeal 18118

2014 OSSC 404.5, 909 Smoke Control

A smoke control system shall be installed in accordance with Section 909.

ORIGINAL TEXT:
An 140'-4 1/2" (L) X 11'-11 1/2 (W) x 49'-6 1/2" (H) atrium, which is open to atmosphere on two sides, is covered by a series of 24 smoke control skylights, spaced evenly along the length of the atrium (see exhibit 1). The smoke control skylights are opened fully when water flow through the sprinkler system occurs, or by a fuseable link at 165 degrees, whichever occurs first. This building is Type IIIA construction.

The open skylights result in 768 s.f. total of open area spanning the length of the atrium. The North end of the atrium is completely open (no walls), and the South end is open on floors 2 and 3. The North side is approx. 394 s.f. open, and the South side is approx. 148 s.f. open, resulting in a total of 1,310 s.f. of openness to atmosphere (see exhibit 2).

Circulation is the main use of the atrium space. Each apartment is separated from the atrium space by a 1-hour fire wall as required by code, and all units are separated from each other by a 1-hour fire separation, exceeding separation requirements by code. Each unit is provided with self-closing rated entry doors from the atrium. There are ¾ hour rated windows in the 1-hour wall between the atrium and the units, in accordance with Table 716.5, Opening Fire Protection Assemblies, Ratings and Markings. All mechanical openings into the atrium will have rated combination fire/smoke dampers of 1.5 hours, in accordance with Table 717.3.2.1, Fire Damper Rating.

In the floor between the apartment unit entries are open areas, allowing light and air to travel freely between floors in the atrium. This horizontal open area results in approximately 333 s.f. of open area on each floor, resulting in 1,332 s.f. of openness between floors. (see exhibit 3).

Smoke detectors, a fire alarm system and an automatic sprinkler protection system will be provided throughout the entire building, including the atrium.

Please see Exhibit 4 for a detailed Performance-Based Design Fire Modeling Report.

RECONSIDERATION TEXT:
Based on conversations with the fire reviewer for this appeal, we propose heat and smoke vents along the length of the top of the atrium in lieu of a smoke control system in accordance with Section 909. The heat and smoke vents will conform to NFPA 72 and NFPA 204. We have provided smoke modeling that shows that the heat and smoke vents proposed provide equivalent life safety to code requirements by allowing smoke to exit the building adequately without a smoke control system.

Record high temperature is 107 in 1965 & 1981. The higher the temperature the greater the likelihood of stratification. Fire Modeling was done using exterior temperatures of 107F or 41.667C. A smoldering fire was not modeled as smoke production is a function of heat release rate and the heat produced by a smoldering fire would be very low thus smoke would stratify at a lower level not affecting all floors potentially. Temperatures at the doors range from 107F (ambient) to 160F in the fire plume area on the walking platform. The heat/smoke vent will be activated electrically but fusible link is already built in as a redundancy.

Consistent with the building code, this model assumes occupants will egress upon fire alarm activation because occupant behavior is case by case. The atrium walls will have a minimum 1-hour fire separation. Please refer to the fire modeling report (exhibit 4) for more detail on egress time calculations, built in pre-movement delays, and built in safety factor increases.

We have increased the hazard classification in the atrium from Low Hazard to Ordinary Hazard, Group 1 to increase the requirements for sprinkler coverage in the atrium space, providing more assurance of sprinkler effectiveness in the event of a fire in the atrium.

In response to the concern that the backup fuseable link would activate the smoke vents before the sprinkler could activate, we propose to use sprinklers that activate at 165 degrees maximum, and fuseable links that open the heat and smoke vents at 212 degrees. This difference in activation temperature will ensure that the sprinklers activate in the event of a fire.

We have included the information related to the heat and smoke vents in the revised fire modeling report (exhibit 4), which includes information that shows that the springs open with enough force for 10 psf of snow load. To minimize buildup, we have also adjusted our curb design to slope all skylights at ¼” per foot for drainage (see exhibit 5).

ORIGINAL TEXT:
The alternate is required because the atrium is designed to be passively smoke evacuated, but does not follow the prescriptive path in the code. We have provided a smoke modeling report to present a code equivalent design.

Please see Exhibit 4, the Performance Based Design Fire Modeling Report, which includes the full results and analysis of the CFD modeling of the atrium area. A summary is as follows, page 54 of the Fire Report. " Based on the configuration of the space without the support of a smoke exhaust system the space is unable to maintain tenable conditions throughout egress. Therefore, vents located at the ceiling are required to exhaust the smoke out of the atrium and help maintain tenable conditions. The vents are to be activated upon initiation of any zoned atrium or apartment sprinkler. The 24 vents, located on the ceiling, allow the smoke to travel up and out of the atrium space, allowing for lower visibility for the occupants. Without the vents, the atrium would become untenable before occupants are able to egress from the space. Make-up air velocities shall not exceed 200 feet/min. "

Based on the information submitted in our fire modeling report, this design provides an equivalent level of fire and life safety to having a mechanical smoke control system.

RECONSIDERATION TEXT:
The alternate is required because we propose heat and smoke vents along the length of the top of the atrium in lieu of a smoke control system in accordance with Section 909. We have provided a smoke modeling report to present a code equivalent design. Exhibit 4, the Performance Based Design Fire Modeling Report, has been revised to include responses to concerns in the original appeal, including the following; fuseable links that open the heat and smoke vents at 212 degrees to ensure sprinkler activation, information about the opening force of the heat and smoke vents, and increased sprinkler design to meet Ordinary Hazard, Group 1 requirements rather than the code allowed Low Hazard classification. Based on the information submitted in our fire modeling report, the heat and smoke vents along the length of the top of the atrium provide equivalent life safety to a code required smoke control system in accordance with Section 909.

2014 OSSC 404.7 Standby Power

Equipment required to provide smoke control shall be connected to a standby power system in accordance with Section 909.11.

ORIGINAL TEXT:
The smoke control skylights proposed have two triggers to activate. The first is a low voltage connection from a flow sensor in the sprinkler system, which will open the skylights in the event of water flow. The second is a fail safe fuseable link, which will open the skylights when the temperature reached 165 degrees. This is the same temperature as the fire sprinkler activation. The fuseable link requires no power to activate.

Due to the passive fuseable link, which does not require power to activate, the smoke ventilation will still be completely functional in the event of a power outage.

RECONSIDERATION TEXT:
We are proposing heat and smoke vents that will conform to NFPA 72 and NFPA 204 in lieu of a smoke control system in accordance with OSSC Section 909. Because we are not providing that system, and the heat and smoke vents are activated via water flow or a fuseable link, no standby power is required for the heat and smoke vents to function.

ORIGINAL TEXT:
Due to the passive fuseable link, which does not require power to activate, the smoke ventilation will still be completely functional in the event of a power outage. The CFD modeling report and analysis provided by the fire protection engineer confirms that natural passive ventilation is sufficient based on the proposed design. Therefore, no equipment is required to be connected to standby power.

RECONSIDERATION TEXT:
We are proposing heat and smoke vents that will conform to NFPA 72 and NFPA 204 in lieu of a smoke control system in accordance with OSSC Section 909. Because we are not providing that system, and the heat and smoke vents are activated via water flow or a fuseable link, no standby power is required for the heat and smoke vents to function.