Smoke Detector and Sprinkler Activation Times with Gas Burner Fires using BRANZFIRE

Abstract

*† Lilley & Associates, 7221 Idlewild Acres, Stillwater, Oklahoma 74074 BRANZFIRE is an efficient zone type computer fire modeling software used to simulate fires in multi room structures. Its name is an abbreviation for Building Research Association of New Zealand FIRE model. This modeling software can calculate various important variables involved in a fire scenario like the upper layer and lower layer temperatures, optical smoke density, smoke detector, heat detector and sprinkler activation times. It has got a wide variety of predefined fires and many other fires in their fire database (University of Canterbury, New Zealand online database). BRANZFIRE under predicts the activation times of smoke detectors but over predicts the activation times of sprinklers, as stated in the validation provided by the computer code developers. It is applied here to the calculation of smoke detector and sprinkler response time calculation with a variety of standard gas burner fires. A single room, closed door, wall fire scenario is used to run various simulations using BRANZFIRE computer fire modeling software. Smoke detectors and sprinklers are located on the ceiling every 0.5 meters away from directly above the fire. Three different smoke detector sensitivities are considered in all cases, to exemplify the effect of sensitivity on the activation times. Sprinkler sensitivity was held constant at standard settings of activation temperature, C-factor and response time index RTI. Activation times of smoke detectors and sprinkler operation are calculated for a varity of standard gas burner fires and compared with corresponding times from standard t 2 -fires with varying heat release rates: the ultra-fast, fast, medium and slow fires. Results obtained from BRANZFIRE simulation indicate that the constrained heat release rate falls below the specified heat release rate in most of the cases, because of lack of availability of oxygen as the smoke descends in the closed room. Smoke detector activation times depend upon the rapidity of fire development, detector sensitivity, and proximity of the detector to the location of the fire. When detectors are closer to the fire, detector sensitivity plays a less important role.