Smoke detectors and heat activated sprinklers are two devices used in fire safety engineering to aid in the evacuation of people and to prevent the spread of fires. Sprinklers and detectors are both considered detection devices by CFAST model and are handled using the same input keywords. Detection is based upon heat transfer to the detector. Fire suppression by a user-specified water spray begins once the associated detection device is activated. We start with the one compartment scenario used earlier (TwoCompartmentsStep1). Add the line
DETECT,1,1,301.15,1.5,1.5,4.9,100,0,7E-05
to enable a smoke detector. Note the temperature setting of 301 K. This is 8 C above the ambient of 293 set in the ambient section. If the ambient is changed in the GUI, then this value needs to be changed as well. It is not done automatically. This is the base case.
Then to enable a sprinkler, add
DETECT,2,1,344.15,1.5,1.5,4.9,100,1,7E-05.
The format is the same for both detection systems; however, the spray density of 7x10-5 does not apply to a smoke detector. In this case, the trigger temperature is 344 K which is 71 C and characteristic of standard sprinklers. This value is not relative to the ambient.
Three scenarios illustrate the output from the model:
#1) A sprinkler with an activation temperature of 71 C, an RTI of 100, and spray of 7x10-5 m/s.
#2) A sprinkler with T=71 C, RTI=75, and spray=7x10-5.
#3) A sprinkler with T=71 C, RTI=50, and spray=7x10-5.
4) A smoke detector
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The smoke detector responds the fastest. Case #1 is the slowest with an RTI of 100, Cases #2 and #3 activating sooner with RTIs of 75 and 50 respectively.
