A Review of Building Evacuation Models - NIST Virtual Library

• Occupants stop investigating if they are in a room where S>0.05. They will stop
investigating before entering a room where S>0.1
• If the occupant is in a room where S>0.1, he/she will respond more quickly and believe the
fire is more serious.
• Penalties and demerits are assigned to a route where S>0.4
The occupants are assigned certain characteristics for a simulation and those are age, sex, normal
walking speed, whether or not the occupants have special needs, whether or not the person is
sleeping, room location, and difficulty of waking up.
There are two types of occupants within the model, those fully capable when awake and those
who are in need of assistance to evacuate the building. Decision rules apply only to the first
group, and the latter group only follows those decisions and movements made by their rescuers.
Capable occupants become aware of the fire through cues, such as the sound of a smoke
detector, odor of smoke, visible smoke, and visible flame. The model follows a basic equation
for if and when an occupant will begin responding to a cue, and suggests the work of Nober 65 is
the formulation of this equation. Equation A.4 is the cue equation, which assumes that the
occupant’s response is a function of the sum of impacts from sensory cues:
T = 70 – 4(C-20) and C = (A-N) + X 1 + X 2 + X 3 + X 4
(A.4)
where T is the delay time before beginning the first action, C is the sum of sensory impacts on
the occupant, A is the sound intensity of the smoke detector as heard by the occupant, N is the
background noise, X 1 is the impact of an occupant seeing flame, X 2 is the impact of the occupant
smelling smoke, X 3 is the impact of an occupant seeing smoke, and X 4 =0 if occupant is sleeping
and 15 if the occupant is awake. X 1 and X 3 = 0 if the occupant is asleep.
EXITT normally assigns investigation as the first action of the occupant. Exceptions to this
include if an occupant has completed investigation, if there is bad smoke in the room, if the
occupant has been alerted by another who has seen bad smoke, or if the occupant is an adult
female with an infant that needs help. The occupants have other alternative actions in the case
that the exceptions apply (in this specific order) which are help an occupant in the same room,
help an occupant in a different room, investigate, and egress. Occupants over age 10 act in the
same way as an adult would.
Any delay time, decision time, and time to perform actions depend on the occupant
characteristics, fire environment, and the impact of the fire cues onto the occupants.
An addition to the model includes the option for users to override the decision rules and study
the effect of alternative decisions.
Occupant movement: As mentioned earlier, a normal walking speed is assigned to each
occupant by the user, and throughout the simulation, speeds are altered in the following way:
• 30 % faster than normal if the occupant considers the fire to be serious
A-46