NFPA Journal - May/June 2017 - 38

In Compliance
possible to meet the fire protection
goals, the designer can then use the
spacing requirements of NFPA 72.
Non-smooth ceilings-beams, joists, or
other obstructions-present a challenge
for the spacing of smoke detectors, and
it's worth highlighting two of the most
common issues that affect spot-type
smoke detector spacing for non-smooth
ceilings. Section 17.7.3.2.4.2 provides
spacing guidance based on beam depth
as a percentage of ceiling height. The
more difficult application occurs when
the beams form a "waffle type" ceiling
configuration. In such applications,
depending on the ceiling height, detectors will either reside in the beam pocket
or on the bottom of the beams.
A research report prepared for the
technical committee by the Fire Protection Research Foundation found that
"the geometry and reservoir effect is
a significant factor that contributes to
the development of velocity, temperature, and smoke obscuration conditions
at smoke detectors located on the
ceiling in beam pocket areas or at the
bottom of beams as smoke collected in
the reservoir volume spills into adjacent pockets." The report found that the
waffle- or pan-type ceiling created by
beams or solid joists, while retarding
the initial flow of smoke, can result in
increased optical density, temperature
rise, and gas velocities comparable to
unconfined smooth ceilings. For those
types of ceilings, the report advised,
"an alternative smoke detector grid
arrangement (such as a shifted grid),
with detectors located to take advantage of the channeling effect due to the
reservoirs created by the beam pockets,
will improve detector response and
might allow greater spacing."
The model building codes and NFPA
101®, Life Safety Code®, often require
corridor smoke detection. When beams
occur in these spaces, the code offers
additional guidance. Corridor spacing is
based on the width of the corridor not
exceeding 15 feet, with assumed ceiling
heights of 10-12 feet. When the beams
(or solid joists) exist perpendicular to
the corridor length, smooth ceiling spacing shall be permitted, and the location
of spot-type smoke detectors on ceilings,

38 | NFPA JOURNAL * M A Y / J U N E 2 0 1 7

sidewalls, or the bottom of beams or
solid joists shall be permitted. So, in
fact, corridor spacing of spot-type smoke
detectors can prove relatively easy given
the prescribed conditions.
The important takeaway from this
discussion is that although following the
code for the device installation requirements is important, it becomes equally,
if not more important, to meet the fire
protection goals of the owner and to
fully understand how smoke will be
transported to the detector for efficient
detection to occur. I encourage readers
to study this entire section of the code
and the related Annex A material for
spot-type smoke detector placement in
beamed ceiling configurations.
Wayne D. Moore is vice president at Jensen
Hughes. NFPA members and AHJs can use the
Technical Questions tab to post queries on NFPA 72
at nfpa.org/72.

NFPA 101

Life safety in new and
existing structures

NFPA 101 and change-ofoccupancy issues
By Ron Coté

he "Ghost Ship" warehouse fire, which
occurred in December in
Oakland, California, and
killed 36 occupants, was
a tragic large-loss-of-life incident where
a building was used as an occupancy
different than what it was permitted
for. Additionally, the authority having
jurisdiction was not aware of that new,
unpermitted use. Adoption and enforcement of fire and life safety codes, such
as NFPA 101®, Life Safety Code®, can help
to prevent similar tragedies.
NFPA 101 is an occupancy-based
code, meaning that the features, systems, and other protective elements
required by the code vary depending
on occupant needs and capabilities that
are characteristic of each occupancy
type. For example, the health care

T

occupancy provisions employ a protectin-place strategy whereby the required
features work together to keep the nonfire portions of a building tenable for
use as areas of refuge while the fire is
being controlled.
Contrast the required health care
occupancy protection scheme with that
applicable to an assembly occupancy,
such as a restaurant with seating for
more than 300. The restaurant occupants are expected to egress the building
upon fire or similar emergency. The
requirements that work together to
provide sufficient egress time include a
means for providing voice emergency
messages via the building fire alarm
system; automatic fire sprinklers to keep
the fire from spreading to points outside
the area of fire origin; and fire-resistive
building construction to help ensure
that the building does not collapse
before all building occupants have
escaped. Other required features work
to complete the package providing the
needed level of life safety. For example,
the main entrance/exit of the restaurant
is required to provide a minimum of
one-half of the required egress capacity
because occupants, under fire emergency conditions, will try to return to
the entrance with which they are familiar, potentially overtaxing this egress
route compared to other routes that may
be underutilized.
NFPA 101 addresses change of
occupancy in Chapter 43, Building
Rehabilitation. Change of occupancy is
one of the rehabilitation work categories for which specialized requirements
apply. (The other rehabilitation work
categories are repair, renovation, modification, reconstruction, change of use,
and addition.) With change of occupancy, the code user notes the hazard
category of the existing occupancy and
the hazard category of the new occupancy, as defined and classified in the
building rehabilitation chapter.
If the new occupancy is of a greater
hazard category than the existing occupancy-for example, if a warehouse is
changed to a nursing home-then the
new occupancy must meet all of the
applicable requirements, in this case
for a new health care occupancy.
http://www.nfpa.org/72
Table of Contents for the Digital Edition of NFPA Journal - May/June 2017
