Security Sales & Integration February 2023 - 19

EXECUTIVE DECISIONS
Security Science by Jeff rey Zwirn
jeff zwirn@alarmexpert.com
How Safe Egress Times Impact
Proper Life-Safety Design
▶ FIRE PROTECTION ENGINEERS know
Alarm and
security
professionals
should
recognize the
concepts of
ASET and RSET
as part of the
life-safety fi re
alarm system
services it
provides.
that the goal in fi re-safe building design is to
evacuate or relocate occupants to a place of safety
before they are subjected to untenable conditions
produced by the fi re (e.g., heat, smoke, toxic
gases). Th e time it takes to evacuate an occupant
to a place of safety is known as the Required Safe
Egress Time (RSET) - this includes pre-evacuation
(or pre-movement) time as well as evacuation
(or movement) time.
Th e pre-evacuation period in a fi re is the timeframe
between the ignition and the occupant's
decision to take action. During the pre-evacuation
period, cues related to the fi re are present. To
act, the occupant must receive the cue, which is a
combination of sensing it, paying attention to it,
and comprehending it.
An occupant may receive fi re cues from the fi re
Jeff rey Zwirn, CPP, CFPS,
CFE, FACFEI, CHS-IV, SET,
CCI, FASI&T, MBAT, is a
forensic alarm expert &
President of IDS Research
& Development.
securitysales.com
environment (e.g., smell of smoke), the building
(e.g., activation of an audible/visual alarm),
or other people in the building (e.g., yelling that
there is a fi re). After receiving a cue, the occupant
then processes the information to determine if a
threat is present and decides to take action or resume
their normal activity (no threat).
Any delay in the presence, receipt or processing
of cues can substantially expand this pre-evacuation
period. Safe building design ensures that
the Available Safe Egress Time (ASET) exceeds
RSET. ASET is the time between the ignition of
the fi re and an endpoint that hinders the ability of
an occupant to safely escape (e.g. reduced visibility,
heat, toxic gases) to successfully get out before
being exposed to smoke, heat and toxic gases.
Exposure to toxic products of combustion occurs
when there is a fi re and the available time to
safely escape is less than the time needed. Th e time
at which conditions become untenable (ASET) is
the time at which the amount of smoke or heat,
as calculated by a fi re model or similar tool, fi rst
exceeds pre-established tenability criteria. Sample
criteria for determining ASET might be:
1. Temperature conditions
2. Visibility conditions
3. Carbon monoxide concentrations
Alarm and security pros should recognize
the concepts of ASET and RSET as part of the
life-safety fi re alarm system services it provides.
It could make the diff erence between occupants
being escaping a fi re before the premises becomes
untenable or not being able to escape/survive.
Stick to Strict Technical Standards
From an alarm science perspective, we need to
focus on foreseeable vulnerabilities the subscriber
should be educated on as to the diff erences
between the minimum vs. exceeding minimum
NFPA 72 Standards. Th at means why having the
proper quantity of smoke detectors exceeding the
minimum requirements of NFPA 72 throughout
the occupancy is an important consideration over
low-cost one-size-fi ts-all approach (and that usually
goes for electronic security as well, such as
installing three door contacts, a motion detector
and/or one smoke detector in the " best " location).
Equally important is for the alarm contractor
to never deviate from strict compliance to the
minimum/mandatory audibility requirements of
NFPA 72. Authoritative, written proof that calibrated
sound level testing was verifi ed in accordance
with NFPA 72 in the protected premises
should be integral to all fi re alarm systems.
Regarding other technical aspects of life-safety
systems, if any of the occupants in a commercial
occupancy cannot self-rescue, the property manager/owner
needs to know and the AHJ has to be
involved in the next step of the life-safety paradigm
- fi re alarm systems cannot perform their
intended objectives if anyone cannot self-rescue.
Finally, the property manager/owner should
survey the building occupants annually to help
with persons who cannot self-rescue and advise
all persons living at the property that if they are
handicapped (or become handicapped in the future)
they need to advise the property manager/
owner in writing so an action plan for each of
the persons who cannot self-rescue is put in place
by the AHJ. Consequently, emergency personnel
are put on notice and can prepare to evacuate
these persons before a fi re. Occupants moving
into an apartment for the fi rst time should also
receive this notice.
FEBRUARY 2023 Security Sales & Integration
19
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Security Sales & Integration February 2023

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