Issue: DS 2015-075. The Petitioner Ms. Sheila Oliver is requesting clarification concerning the placement of smoke duct detectors for the air conditioning and exhaust systems.
Questions:
Background:
Situation: During a preliminary design and review meeting with the design engineers for a (6) six story mixed use facility, the Engineering firm requested clarifications for their Mechanical design based on the new 2014 Code which they will be submitting under. In order to direct them properly, I am seeking clarification in regards to the placement of smoke duct detectors for the air conditioning and exhaust systems. As the building is less than 75 feet in height, there will be no smoke control systems as per Chapter 9-section 909, of the Florida Building Code- 5th Edition (2014). Therefore, these detectors are strictly required based on the cfm capacity of the air conditioning and exhaust systems only.
Summary: Based on Manufacturer’s Technical Field Bulletin as well NFPA 72 – Annex A (Explanatory Material) A.17.7.5.5.2, the primary function for the duct mounted smoke detection was and is to serve the purpose of shutting down the HVAC system or to initiate smoke management. Smoke detectors are installed in the supply air, downstream from the filters, to serve the purpose of providing an alarm indication of the occurrence of a fire in the HVAC unit (filters, belts, heat exchangers, etc.). These detectors usually serve the purpose of protecting building occupants from the smoke produced by an HVAC unit fire or smoke ingress via the fresh air intake for the unit. They cannot be expected to serve the purpose of providing detection for the return side of the system.
Florida Statutes:
553.73 Florida Building Code.—
(1)(a) The commission shall adopt, by rule pursuant to
ss. 120.536(1) and 120.54, the Florida Building Code which shall
contain or incorporate by reference all laws and rules which pertain to and
govern the design, construction, erection, alteration, modification, repair,
and demolition of public and private buildings, structures, and facilities and
enforcement of such laws and rules, except as otherwise provided in this
section.
……
(d) Conflicting requirements between the Florida
Building Code and the Florida Fire Prevention Code and Life Safety Code of the
state established pursuant to ss. 633.206 and 633.208 shall be resolved by agreement between the commission and
the State Fire Marshal in favor of the requirement that offers the greatest
degree of lifesafety or alternatives that would provide an equivalent degree of
lifesafety and an equivalent method of construction. If the commission and
State Fire Marshal are unable to agree on a resolution, the question shall be
referred to a mediator, mutually agreeable to both parties, to resolve the
conflict in favor of the provision that offers the greatest lifesafety, or
alternatives that would provide an equivalent degree of lifesafety and an
equivalent method of construction.
Note: term “conflict” as it applies to the Code. It
was previously established by the Joint TAC that for the purpose of the study,
that a conflict was defined as “a construction specification such as a
dimension in one code that would prevent compliance with another code”.
2010 Florida
Building Code, Mechanical
606.2 Where required.
Smoke detectors shall be installed where indicated in Sections 606.2.1 through 606.2.3 and NFPA 90A.
Exception: Smoke detectors shall not be required where air distribution systems are incapable of spreading smoke beyond the enclosing walls, floors and ceilings of the room or space in which the smoke is generated.
606.2.1 Supply air systems.
Smoke detectors shall be installed in supply air systems
with a design capacity greater than 2,000 cfm (0.9 m3/s) in the supply air
duct.
Exception: Smoke detectors are not required in the supply air system where the space served by the air distribution system is protected by a system of area smoke detectors in accordance with the Florida Fire Prevention Code. The area smoke detector system shall comply with Section 606.4.
606.2.2 Common supply, return air and supply air systems.
Where multiple air-handling systems share common supply or return air ducts or plenums with a combined design capacity greater than 2,000 cfm (0.9 m3/s), the return air and supply air system shall be provided with smoke detectors in accordance with Section 606.2.1.
5th
Edition (2014) Florida Building Code, Mechanical
SECTION
606 SMOKE DETECTION SYSTEMS CONTROL
606.2.1 Return
air systems. Smoke
detectors shall be installed in return air systems with a design
capacity greater than 2,000 cfm (0.9 m3/s), in the return air duct or plenum
upstream of any filters, exhaust air connections, outdoor air connections,
or decontamination equipment
and appliances.
Exception: Smoke detectors
are not required in the return air system where all portions of the building served
by the air distribution system are protected by area smoke detectors connected
to a fire alarm system in accordance with the Florida Fire Prevention Code. The area smoke detection system shall comply
with Section 606.4.
[F] 606.3
Installation. Smoke
detectors required by this section shall be installed in accordance with
NFPA 72. The required smoke detectors shall be installed to monitor the entire
airflow conveyed by the system including return air and exhaust or relief air.
Access shall be provided to smoke detectors for inspection and maintenance.
5th Edition (2014) FBC, Building
CHAPTER 1 SCOPE
AND ADMINISTRATION
[A] 102.4
Referenced codes and standards. The codes and standards referenced in
this code shall be considered part of the requirements of this code to the
prescribed extent of each
such reference
and as further regulated in Sections 102.4.1 and 102.4.2.
[A] 102.4.1
Conflicts. Where
conflicts occur between provisions of this code and referenced codes and
standards, the provisions of this code shall apply.
FFPC 101:9.2
Heating, Ventilating, and Air-Conditioning
9.2.1 Air-Conditioning,
Heating, Ventilating Ductwork, and Related Equipment.
Air-conditioning,
heating, ventilating ductwork, and related equipment shall be in accordance with
NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating
Systems, or NFPA 90B, Standard for the Installation of Warm Air
Heating and Air-Conditioning Systems, as applicable, unless such
installations are approved existing installations, which shall be permitted to
be continued in service.
NFPA 90A, Standard for the Installation of Air-Conditioning
and Ventilating Systems 2012 Edition
6.4.2.1 Smoke detectors
listed for use in air distribution systems shall be located as follows:
(1)
Downstream
of the air filters and ahead of any branch connections in air supply systems having a capacity greater than 944 L/sec (2000 ft3/min)
(2)
At
each story prior to the connection to a common return and prior to any
recirculation or fresh air inlet connection in air return systems having a
capacity greater than 7080 L/sec (15,000 ft3/min) and serving more
than one story
6.4.2.2 Return system
smoke detectors shall not be required where the entire space served by the air
distribution system is protected by a system of area smoke detectors.
6.4.2.3 Smoke detectors
shall not be required for fan units whose sole function is to remove air from
the inside of the building to the outside of the building.
6.4.4 Installation.
6.4.4.1 Smoke detectors
shall be installed, tested, and maintained in accordance with NFPA 72, National Fire Alarm and Signaling Code.
NFPA 72, National Fire Alarm and Signaling
Code, 2010 Edition
17.7.4 Heating,
Ventilating, and Air-Conditioning (HVAC).
17.7.4.2.2* Detectors placed
in environmental air ducts or plenums shall not be used as a substitute for
open area detectors. Where detectors are used for the control of smoke spread,
the requirements of 17.7.5 shall apply. Where open area protection is required,
17.7.3 shall apply.
17.7.5* Smoke
Detectors for Control of Smoke Spread.
17.7.5.1*
Classifications. Smoke detectors installed and used to prevent smoke spread by initiating
control of fans, dampers, doors, and other equipment shall be classified in the
following manner:
(1)
Area detectors that are installed in the
related smoke compartments
(2)
Detectors that are installed in the air duct
systems
(3)
Video image smoke detection that is installed
in related smoke compartments
17.7.5.2.1 Detectors that are
installed in the air duct system in accordance with 17.7.5.1(2) shall not be
used as a substitute for open area protection.
17.7.5.3.1 To prevent the recirculation
of dangerous quantities of smoke, a detector approved for air duct use shall be
installed on the supply side of air-handling systems as required by NFPA 90A, Standard
for the Installation of Air-Conditioning and Ventilating Systems, and
17.7.5.4.2.1.
17.7.5.4
Application.
17.7.5.4.2.1
Supply Air System. Where the detection of smoke in the supply air
system is required by other NFPA standards, a detector(s) listed for the air
velocity present and that is located in the supply air duct downstream of both
the fan and the filters shall be installed.
17.7.5.4.2.2*
Return Air System. Unless otherwise modified by 17.7.5.4.2.2(A) or
17.7.5.4.2.2(B), if the detection of smoke in the return air system is required
by other NFPA standards, a detector(s) listed for the air velocity present
shall be located where the air leaves each smoke compartment, or in the duct
system before the air enters the return air system common to more than one
smoke compartment.
(A) Additional
smoke detectors shall not be required to be installed in ducts where the air
duct system passes through other smoke compartments not served by the duct.
(B)
Where total coverage smoke detection is
installed in all areas of the smoke compartment served by the return air
system, installation of air duct detectors in the return air system shall not
be required, provided that their function is accomplished by the design of the
area detection system.
Note: See
attached commentary from the 2012 IMC.
Analysis:
Question #1: Section 606.1 is requiring the smoke detectors to be placed in the return air of an a/c unit over 2000 cfm and/or in the exhaust duct of a fan system. Section 606.3 is requiring me to utilize NFPA 72 for installation which requires it in the supply side. Therefore, does 606.1 supercede 606.3?
Answer: Yes, with regard to placement of smoke detectors and as per Section 102.4.1 of the 5th Edition (2014) FBC, Building, Section 606.1 supercedes the provisions of section 606.3 of the 5th Edition (2014) FBC, Mechanical.
Question #2: If the answer is yes, then since the Florida Fire Prevention Code also calls for it to be installed in the supply air (NFPA 72 and NFPA 90A) whose code takes jurisdiction, fire or mechanical?
Answer:
Option #1: As per the definition of the term “conflict” “see note above”, the project in question must meet both codes.
Option #2: As per the 5th Edition (2014) Florida Fire Prevention Code, NFPA 72 and NFPA 90A, placement of smoke detectors in the supply air system provide for a greater degree of life safety than placement of the smoke detectors in the return air system as required by section 606.1 of the 5th Edition (2014) FBC, Mechanical. Therefore, placement of the smoke detectors in the supply air system takes precedence.
Option #3: As per the 5th Edition (2014) Florida Building Code, Mechanical, placement of smoke detectors in the return air system provide for a greater degree of life safety than placement of the smoke detectors in the supply air system as required by the 5th Edition (2014) Florida Fire Prevention Code. Therefore, placement of the smoke detectors in the return air system takes precedence.
Option #4: Placement of smoke detectors in either the return or the supply air system will provide an equal degree of life safety. (See Section 553.73 (1)(d), Florida Statues)
Question #3: Since the original intent of the installation of these smoke duct detectors was to protect the building occupants if the fire and or smoke was to occur in the unit, is this no longer the purpose?
Answer: Not possible. Addressing “intent” is outside the scope of the Dec. request.
Question #4: By installing the smoke duct detectors in the exhaust duct of a fan system, is it now the intent to stop the products of combustion from exiting to the outside?
Answer: Not possible. Addressing “intent” is outside the scope of the Dec. request.
Question #5: By not installing the smoke detectors in a supply fan system, is it the intent to keep these fans operating, even if the fan is bringing in smoke from an adjacent area or from the fan itself?
Answer: Not possible. Addressing “intent” is outside the scope of the Dec. request.