MS in Fire Protection Engineering
College of Engineering
Frederick Mowrer and Christopher Pascual
A prescriptive analysis of the project building was conducted using the 2016 California Building & Fire Code along with current codes and standards pertaining to specific elements. Encompassed in this analysis is a review of the project building’s structural fire protection, water-based suppression systems, fire detection and alarm systems, smoke control and occupant egress.
Void of construction documentation, the analysis of the structural fire protection of the building was determined by evaluating the current design and use. The restricting factor that determine the construction type was the assembly use on the 6th floor. Other than Type I construction, assembly use is limited to no greater than the 5th floor when the sprinkler increase is applied to the height. Therefore, Type IB was selected as the construction classification. Type IB was selected over Type IA because it is a more appropriate designation for the current design and use of the building. Type IA has less restriction compared to Type IB in terms of building height and use, but it is an unnecessary increase in construction cost for the project building’s design and use.
Since I was not provided with any sprinkler information, a simple layout had to be assumed based on observations. During inspection of the project building, a single four-inch riser was found in the northeast stair enclosure which was assumed to serve all portions of the building. Using the small room method, three areas were selected as the focus of the hydraulic calculations conducted to determine the most remote sprinkler demand. The areas that were evaluated were the most remote office (Light Hazard) and building support spaces (Ordinary Group 1 Hazard) located on the 6th floor and the main lobby located on the 1st floor. The hydraulic calculations were conducted using an assumed sprinkler piping layout that led back to the single riser. The analysis yielded a total demand (including hose stream allowance) of: 241.7 gpm at 71 psi for the office space, 331.7 gpm at 50.4 psi for the building support space and 215.6 gpm at 31.4 psi for the main lobby. The evaluation showed that the assumed city water supply met the demand from the most remote area within the building.
With limited building access, the alarm and detection device information was limited to what was observed within the project building. During inspections, it was determined that the building was fitting throughout with a Siemens emergency voice alarm communication (EVAC) system and Siemens multi-criteria heat and smoke detectors. I was provided one time access to the fire command center where I discovered a Siemens Cerberus Pyrotronics Fire Alarm Control Panel. After the fire alarm and detection device inspections, it was determined that the spacing and placement of these devices complied with the requirements of NFPA 72.
When the building was first constructed an active smoke control system was required by the City of El Segundo municipal code. However, during my time in the fire command center, I noticed that the new smoke control panel had only controls for the HVAC system and the fire dampers. Therefore, I concluded that during the recent renovation, the fire protection engineer developed an alternate method of design to decommission the active smoke control system and substitute it with a passive system. I also discovered that all the office doors were 20- minute rated ‘S’ labeled doors which would mean the corridors are designed as 1-hour rated corridors. While not required, it is assumed that the corridors were upgraded as a substitute for decommissioning the active smoke control system.
The performance-based analysis was performed using computer modeling software such as Fire Dynamic Simulator (FDS), Pyrosim and Pathfinder. A set of tenability criteria were developed so to evaluate the performance of the project building during a selected fire scenario. The fire scenario selected for this analysis was a cotton covered chair that is ignited by a spark coming from a nearby outlet that shorts from a coffee spill. The criterion limits were 4 meters of visibility 6 feet above the floor, exposure to 100 ˚C for no more than 10 minutes and exposure to carbon monoxide (CO) concentration of 1,500 ppm for no more than 10 minutes. The design fire stemming from the fire scenario was a 479 kW ultra-fast t-squared fire the developed from a burning polyurethane foam chair. FDS was used to model the design fire and Pathfinder was used to model the occupants on each floor. The results from the two simulations were used in parallel to evaluate the project buildings ability to maintain tenable conditions during the fire scenario. The results of the simulation showed that the project building maintained tenable conditions within the space where the fire scenario was located in regards to exposure to heat and toxic gases, but failed to maintain a visibility of 4 meters.
Since the space where the fire scenario was located is small and enclosed, the smoke accumulated at an accelerated rate which quickly reduced visibility to zero. However, it is important to note that the criterion for visibility was set for a height of 6 feet. This means while visibility does drop below the limit set by the criterion, occupants can crouch or crawl towards exits if they are unable to see while standing up. It is recommended that some form of active smoke control system be employed within this area to reduce the drastic drop in visibility. Either a direct evacuation of smoke within the area via ducts or some form of fans that activate and blow the smoke out the window panels on the exterior walls should be employed to help maintain tenable conditions. Additionally, reorganizing the layout of the space where the furniture is not placed near the outlet can help minimize, and potentially eliminate, this fire scenario.