Fire Protection Options for Air-Supported Dome?

10/10/2022

I am an architect working on a project where we're construction an air-supported structure (dome) for a school district to use as their physical education gymnasium.

The fire marshal here wants the dome fire suppressed.

I told him we cannot hang water piping from the dome.

What are the options to provide fire suppression inside of a air supported structure that is 180 x 135 feet?

Are there alternatives, like water cannons along the perimeter? If so, what kind of costs might that suggest?

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25 Comments

Ray Hardy link

10/10/2022 08:06:35 am

Fill it with Nitrogen?

Franck

10/10/2022 08:46:49 am

That could be problematic for the students ;)
Not to speak about the prohibitive cost of such a system in such a volume.

matt

10/10/2022 08:19:15 am

Can the structure be deflated/turned off? What happens if the air is turned off?

Ralph Giro

10/10/2022 08:25:56 am

There is usually a metal framing system to help hold the fabric in place. I would start by consulting with the supplier of the fabric dome material to get their suggestions. This is not uncommon.

Doug link

10/10/2022 08:33:34 am

Questions:

Will the suppression system use heat detection? What happens when the heat is high enough to set off the suppression system?

If the heat has degraded the nylon roof, will the roof collapse on the crowds of people inside, trapping them?

Would flame detection be better than heat detection?

Glenn Berger

10/10/2022 08:39:28 am

You will need to work with the AHJ on this one. Provide fire suppression in the dome will not happen. But, fire protection would be required in the supporting areas.

Todd Wyatt

10/10/2022 08:46:43 am

You state that the “fire marshal here wants the dome fire suppressed.” An authority having jurisdiction (AHJ) are required to enforce and interpret the adopted Codes, they are not permitted to require Projects to be protected with an automatic sprinkler system (ASPS) because they “want” it unless the Code requires it.

The first step would be determining the Occupancy Classification (OC) for the “air-supported structure (dome) for a school district to use as their physical education gymnasium.” If this air-supported dome structure is for a school for K-12, it could be classified as Group R Educational. Per its assembly use, it could be classified as Group A-3 Assembly (gymnasiums w/o spectator seating) and/or Group A-4 Assembly (viewing of indoor sporting events with spectator seating).

Per 2021 IBC Chapter 9 Fire Protection and Life Safety Systems, Section 903 Automatic Sprinkler Systems identifies when buildings/structures require an ASPS based on their OC.

903.2.1.3 Group A-3
An automatic sprinkler system shall be provided throughout stories containing Group A-3 occupancies and throughout all stories from the Group A-3 occupancy to and including the levels of exit discharge serving that occupancy where one of the following conditions exists:
1. The fire area exceeds 12,000 square feet (1115 m2).
2. The fire area has an occupant load of 300 or more.
3. The fire area is located on a floor other than a level of exit discharge serving such occupancies.

903.2.1.4 Group A-4
An automatic sprinkler system shall be provided throughout stories containing Group A-4 occupancies and throughout all stories from the Group A-4 occupancy to and including the levels of exit discharge serving that occupancy where one of the following conditions exists:
1. The fire area exceeds 12,000 square feet (1115 m2).
2. The fire area has an occupant load of 300 or more.
3. The fire area is located on a floor other than a level of exit discharge serving such occupancies.

903.2.3 Group E
An automatic sprinkler system shall be provided for Group E occupancies as follows:
1. Throughout all Group E fire areas greater than 12,000 square feet (1115 m2) in area.
2. The Group E fire area is located on a floor other than a level of exit discharge serving such occupancies.
Exception: In buildings where every classroom has not fewer than one exterior exit door at ground level, an automatic sprinkler system is not required in any area below the lowest level of exit discharge serving that area.
The Group E fire area has an occupant load of 300 or more.

In all (3) OC, 12,000 SF and an Occupant Load >300 are required parameters for an A-3, A-4, or E to be protected with an ASPS. If your “air-supported structure (dome) for a school district to use as their physical education gymnasium” does not meet either of these requirements, an ASPS is not required regardless of the AHJ’s “preference.”

Please review Section 3102 Membrane Structures for other non-ASPS requirements.

Todd E Wyatt

10/10/2022 08:51:13 am

180 feet x 135 feet = 24,300 SF > 12,000 SF

ASPS would be required for A-3 and A-4 but perhaps not for E.

Franck

10/10/2022 08:52:47 am

As Glenn indicated, it would be more than problematic to provide a water-based fire protection system inside, for several reasons:
- the main one is that there is normally no structure to support the weight of piping, or even to attach the pipes
- the second one might be related to the fabric itself that may not sustain heat and would either burn or open above the location of sprinklers, thus not being able to operate the thermal sensitive element.

Gas protection system is not an option for such a large volume.

But it could be advisable to provide at least some kind of fire detection system (beam detection) as you can normally find a way to locate them inside the structure. This is not a fire suppression system, but at least you will have an alarm that will enable to call the fire department and evacuate the structure.

Greg

10/10/2022 09:22:05 am

One of the ways to explain to the Fire Marshal why sprinklers are complicated in this scenario is the tent material, the suppression angles and the height. Sprinklers are designed to operate within the jet plume of a fire, but the angle presented by the walls of dome create a more likely scenario where the fire will challenge the dome's fabric material ahead of sprinkler activations. This, in combination with the angles needed to suppress with traditional sprinklers make their presence in approximately 2/3rds of the tent impractical. For the 'ceiling' area, the remaining 1/3 is typically too high for the anticipated combustible load to anticipate the jet plume will come near enough to activate the sprinklers. They are likely published studies with similar rational, funded for evaluation of government use of such structures. There is manufacturer who has a water cannon pictured as part of their advertisement, in Arizona https://arizonbuildingsystems.com/wp-content/uploads/2016/09/Fire-Protection-Systems-in-Air-Structures.pdf This was a study of sprung structures, government funded. https://www.osti.gov/biblio/801337 Air supported structure challenges the conclusion reached in the sprung study, but it's the information within the report that is important in this conversation.

For no-water solutions; (1) occupancy use agreement. (2) air-smoke sampling system

Sprinkler any attached or exposing hard structure.

Alex

10/10/2022 11:29:40 am

Hi,

I am extremely curious regarding the architectural/structural design of this dome. I'm sure that is where the AHJ is stuck as well.

I was at a local SFPE event last week where presenters discussed virtual reality within construction. This may be a good project to experiment with the new technology. If I were the AHJ, I wouldn't only be concerned with fire suppression but notification, the dome collapsing, if the dome is on backup power, fire rating of the dome, etc.

Thanks,
Alex

Jesse

10/10/2022 12:12:47 pm

This one has me stumped. I've been a part of many of these types of projects and I don't recall AS protection being a part of ay them.

Connor

10/10/2022 12:39:57 pm

Another consideration is the flexibility and movement of the fabric dome structure. If it were somehow possible to hang the pipe in the first place, the flex of the dome could deform the piping or even cause it to come apart. I would imagine the hazard presented by 3" pipe and fittings falling on a soccer field would warrant consideration.

Dan Wilder

10/10/2022 01:08:09 pm

We've completed one of these is the past with a mix of fixed and manually elevated water powered oscillating monitor nozzle towers, typically in 6 locations (corners and center edges) with a manual override. We did provide sprinkler protection in the connecting egress tunnels (they had a metal scaffold like framework).

It was a lot of water....

Shahpoor Khosravi

10/10/2022 03:34:35 pm

In case you cannot convince the AHJ that the sprinkler is not needed, my suggestion would be to provide monitors with beam detection systems so you would not need to hang pipes from the structure.

Brian Cockburn

10/11/2022 09:47:20 am

Even if it's possible to hang sprinkler pipe from the dome; what happens when the dome is deflated for maintenance, or there's a power outage, or the blowers fail?

David Williams link

10/11/2022 10:00:52 am

The Convention center in Pittsburg uses a "soft" roof. Their solution was to use beam detectors and an automated spray nozzle monitor type system like you would use around petroleum tanks or ships. (I think I was in there 15-20 years ago).

I looked at doing this for a large tennis facility dome, but the project was shelved due to energy code and emergency power required for dome inflation.

Brett

10/12/2022 06:54:18 am

As an AHJ, I will say, this AHJ doesn't know what they're talking about. Early detection and evacuation I can fully support. Fire suppression, no. Ask him to provide code references and actual example projects where fire suppression was provided in a similar structure.

Bill

10/12/2022 08:46:10 am

2018 IBC Section 3102.4 Allowable floor areas. The area of a membrane structure shall not exceed the limitations specified in Section 506.
I'm not finding an exception to providing sprinkler protection for a membrane structure anywhere in the IBC. Not saying there may not be acceptable alternatives in some jurisdictions, but to imply an AHJ doesn't know what they're talking about doesn't seem like the best approach either. I believe the code fully supports that position.
It also appears the group has provided projects that were able to meet the intent of the requirement.

Brett

10/12/2022 09:11:23 am

Bill, I apologize if my comment was harsh. However, in my 20+ years in this field, there are many people (AHJs, Architects, and Engineers) who require things from a position of misunderstanding or ignorance. A more measured response from an AHJ facing such resistance should be to reassess their position. Additionally, I was quick to respond and was merely considering an air supported membrane structure or tent. I did not consider a structure which has membrane portions as sometimes used as architectural elements. In those instances, fire suppression systems are commonly used throughout the structure. However, I've never seen an air supported structure nor a tent style membrane structure with a fire suppression system throughout.
NFPA 101 chapter 11 (using the 2018 edition) covers special structures including permanent membrane and temporary membrane structures as well as tents. Within that chapter there are no requirements for suppression systems. The only suppression related requirement is for portable fire extinguishers. Instead, the code takes the approach of doing everything possible to prevent a fire from occurring including requiring separation within 10 feet of the inside and outside of the structure for membrane structures and 10 feet from outside of a tent structure.
If a fire were to occur in the area within the structure, yes, fire suppression would be nice to have to allow for occupant egress. However, there are so many problems with trying to install a reliable, cost effective system that the project would likely be scraped. However, early detection would provide a much more cost effective solution to providing timely egress of occupants in an emergency. And yes, NFPA codes do consider cost as a factor for an AHJ to consider.

Bill

10/12/2022 09:26:12 am

Brett, although I don't disagree with the benefit of early detection, I'm not sure how you can disregard a requirement from an AHJ perspective. Chapter 11 of the 101 addresses the special structures, such as the one in question, and 11.1.8 specifically requires sprinklers based on the occupancy chapters that would apply.

Bill

10/12/2022 09:36:28 am

Sorry. It should have been 11.1.1

Tom W

10/12/2022 12:03:42 pm

We just finished one up for the Football Hall of Fame in Canton, OH. The use group was listed as an A-3 and under the Ohio Building Code, we are allowed to exclude sprinklers where "Areas used exclusively as participant sports areas where the main floor area is located at the same level as the level of exit discharge of the main entrance and exit." There were 3 auxiliary buildings within the dome itself that we had to install sprinklers in but not the actual dome. I do know they had to have low pressure alarms for the dome in the event of an air loss that would notify the fire dept, as well as smoke detectors and pull stations. The FD did want us to add a few hose valves on the outside of the auxiliary buildings in the dome, but that wasn't a big deal.

10/13/2022 08:48:02 am

There are some relevant special provisions in NFPA 1(2018 Ed.):

NFPA 1:13.3.2.7.2 Any building containing one or more assembly occupancies where the aggregate occupant load of the assembly occupancies exceeds 300 shall be protected by an approved, supervised automatic sprinkler system in accordance with NFPA 13 as follows[...]

NFPA 1:13.3.2.7.3 The requirements of 13.3.2.7.2 shall not apply to the following:
(3)* Locations in stadia and arenas as follows:
(a) Over the floor areas used for contest, performance, or entertainment, provided that the roof construction is more than 50 ft (15 m) above the floor level, and use is restricted to low fire hazard uses
(b) Over the seating areas, provided that use is restricted to low fire hazard uses
(c) Over open-air concourses where an approved engineering
analysis substantiates the ineffectiveness of the sprinkler protection due to building height and combustible loading

Terry

12/13/2022 08:16:58 pm

My company is currently providing fire suppression solutions for the Mercedes’ Benz and Alamo Dome Stadium. We’re currently working on a system for a soccer stadium in Hong Kong. Water cannons are being used along with sprinkler systems for the MB & AD stadiums. The stadiums are used for other activities such as Monster truck events where fuel is stored in the middle of the fields. The water cannons were added as additional fire protection for these stadiums. I’ve also been approached for a basketball facility such as you describes with seating capacity for 3,000 occupants. The structure cannot support a fire suppression system; however, water cannons can be an option when interconnected into automated fire alarm system.

Fire Protection Options for Air-Supported Dome?

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