View Full Version : NFPA 90A - Ducted Pentration in Fire Wall

January 2nd, 2013, 14:13
The problem I have is with the following line in NFPA 90A:

5.3.1 Fire-Rated Walls and Partitions.* Approved fire dampers shall be provided where air ducts penetrate or terminate at openings in walls or partitions required to have a fire resistance rating of 2 hours or more.

Basically I have an air handling unit serving a corridor with a duct. The corridor has less than a 2-hour wall. My original interpration (I'm an AHJ for the Navy) was that a duct could penetrate and cross through the corridor and serve a room on the other side of the corridor. Reading this line makes me think that a penetration is allowed into the corridor. What if the air handling unit burns up? The duct smoke detector, if required at 2000 CFMs or greater would signal a supervisory or fire alarm signal and smoke would fill the corridor. I could be mixing up a mechanical term.

January 2nd, 2013, 14:51
what building / mechanical code are you under???

Normally, if a rated corridor wall is penetrated it is required a damper, with exceptions, per the IBC

plus your building is more then likely sprinkled!!!!!!!!

cannot find the penetration rules for corriodors, readily

January 2nd, 2013, 15:34
Seems to me you got it right, despite the 'what if' part - Corridor less than 2 hour rated? No dampers required.

January 2nd, 2013, 16:32
does nfpa 90A apply:::

1.3 Application.This standard shall apply to all systems for the movement of environmental air in structures that serve the following:

Spaces over 708 m3 (25,000 ft3) in volume

Buildings of Types III, IV, and V construction over three stories in height, regardless of volume

Buildings and spaces not covered by other applicable NFPA standards

Occupants or processes not covered by other applicable NFPA standards

January 2nd, 2013, 16:58
Are you under the IBC? Fire wall? Fire barrier? Fire partition? It may just need to be smoke tight if it does not have any openings in the corridor.....

716.5.2 Fire barriers.

Duct and air transfer openings of fire barriers shall be protected with approved fire dampers installed in accordance with their listing.

Exception: Fire dampers are not required at penetrations of fire barriers where any of the following apply:
1. Penetrations are tested in accordance with ASTM E 119 as part of the fire-resistance-rated assembly.
2. Ducts are used as part of an approved smoke control system in accordance with Section 909.
3. Such walls are penetrated by ducted HVAC systems, have a required fire-resistance rating of 1 hour or less, are in areas of other than Group H and are in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2. For the purposes of this exception, a ducted HVAC system shall be a duct system for conveying supply, return or exhaust air as part of the structure’s HVAC system. Such a duct system shall be constructed of sheet steel not less than 26 gage thickness and shall be continuous from the air-handling appliance or equipment to the air outlet and inlet terminals.

716.5.4 Fire partitions.

Duct penetrations in fire partitions shall be protected with approved fire dampers installed in accordance with their listing.

Exceptions: In occupancies other than Group H, fire dampers are not required where any of the following apply:
1. The partitions are tenant separation and corridor walls in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 and the duct is protected as a through penetration in accordance with Section 712.
2. The duct system is constructed of approved materials in accordance with the International Mechanical Code and the duct penetrating the wall meets all of the following minimum requirements:
2.1. The duct shall not exceed 100 square inches (0.06 m2).
2.2. The duct shall be constructed of steel a minimum of 0.0217 inch (0.55 mm) in thickness.
2.3. The duct shall not have openings that communicate the corridor with adjacent spaces or rooms.
2.4. The duct shall be installed above a ceiling.
2.5. The duct shall not terminate at a wall register in the fire-resistance-rated wall.
2.6. A minimum 12-inch-long (0.30 m) by 0.060-inch-thick (1.52 mm) steel sleeve shall be centered in each duct opening. The sleeve shall be secured to both sides of the wall and all four sides of the sleeve with minimum 1-inch by 1-inch by 0.060-inch (0.038 m by 0.038 m by 1.52 mm) steel retaining angles. The retaining angles shall be secured to the sleeve and the wall with No. 10 (M5) screws. The annular space between the steel sleeve and wall opening shall be filled with rock (mineral) wool batting on all sides.
716.5.4.1 Corridors.

A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air transfer opening penetrates a corridor enclosure required to have smoke and draft control doors in accordance with Section 715.3.3.

1. Smoke dampers are not required where the building is equipped throughout with an approved smoke control system in accordance with Section 909, and smoke dampers are not necessary for the operation and control of the system.
2. Smoke dampers are not required in corridor penetrations where the duct is constructed of steel not less than 0.019-inch (0.48 mm) in thickness and there are no openings serving the corridor.

January 2nd, 2013, 17:55
Thanks for the sanity check. The building is sprinklered. A few people asked what code the Navy uses and the answer is a combination of the IBC and NFPA 101. Basically we use NFPA 101 for egress and the IBC for mostly everything else. This obviously falls into a gray area but we do use NFPA 90A as well. Here is the criteria we adopt incase anyone cares, see page 3:


Your question on applicability is interesting and out of the 15 FPEs we have here nobody has ever brought that up. I may do more research on it. We generally just follow it on every project regardless.

The 2012 International Mechanical Code does seem to echo the same things that you quote above. It looks like a 26 gage duct or greater is considered "equivalent" to a 1-hour wall for duct work.

It looks like a should allow it, although it seems strange to me.

January 2nd, 2013, 18:00
Under the IBC, the one hour rated corridor goes away in a sprinklered building......and the smoke damper goes with ex. 2....

January 2nd, 2013, 20:09
"""""out of the 15 FPEs"""" ok which of the fifteen do we send the consultation bill to???????????

I did not look at the scope of the other 90's to see what they say.

But should start with the base code, prior to jumping to nfpa. Looks like the construction of the corridor and any penetration question, should come from IBC first.


Use UFC 3-600-01 in lieu of IBC Chapter 10.

Use IBC Chapter 7 and UFC 3-600-01. If any conflict occurs between IBC Chapter 7 and UFC 3-600-01, the requirements of UFC 3-600-01 take precedence.

for you all::


ok I see where they get to nfpa:::::

2-4.2 Penetrations.
The protection of ducts at point of passage through firewalls must be in
accordance with NFPA 90A, Installation of Air-Conditioning and Ventilating
UFC 3-600-01
26 September 2006
Change 1, 14 July 2009
Systems, and/or NFPA 90B, Installation of Warm Air Heating and Air-
Conditioning Systems. All other penetrations, such as piping, conduit, and
wiring, through firewalls must be protected with a material or system of the same
hourly rating that is listed by UL, FM, or a NRTL.

2-11.1 Design Requirements
Air handling, heating, ventilation, and exhaust systems must comply with the
requirements of NFPA 90A, except as modified by this UFC.
2-11.2 Corridors.
Egress corridors must not be used as a portion of a supply, return, or exhaust air
system serving adjoining areas. Air transfer opening(s) must not be permitted in
walls or in doors separating egress corridors from adjoining areas.
Exception: Toilet rooms, bathrooms, shower rooms, sink closets, and similar
auxiliary spaces may have air transfer openings, unless prohibited by NFPA 101,
such as in residential occupancies.

January 2nd, 2013, 20:11
nfpa 90B

1.3 Application.This standard shall apply to all systems for the movement of environmental air in structures that serve the following:

One- or two-family dwellings

Spaces not exceeding 708 m3 (25,000 ft3) in volume in any occupancy

Buildings of combustible construction over three stories in height shall be in accordance with NFPA 90A.

January 2nd, 2013, 20:13
I was taught to read the scope from the begining!! has saved me and pi--ed off a few times, when could not find anything to enforce.

January 7th, 2013, 15:35
Yeah 15 guys can still miss things from time to time. You can send the bill to the Navy! The question was also just a general - for my knowledge moving forward. Even though we have 15 guys I figured I would start using the forum to help get a different perspective from time to time. We all sit a few hundred feet apart. I'm the 3rd or 4th most senior and #1 and 2 were out of the office. Thanks again!

January 7th, 2013, 16:18
Yes it is a good idea to get a different prospective