Increasing the hazard of an occupancy arbitrarily - allowed or not?

[fpst]

Let's say you have a typical light hazard occupancy which requires quick response sprinklers, and lets say for whatever reason I don't want to use quick response sprinklers, or can't because of other project considerations.

Is it possible to just arbitrarily increase the hazard to ordinary 1, revise the density accordingly, etc?

 

[ZDR1985]

If you don't want to use water sprinkler system then what do you want?

However, if you consider water sprinkler system and changed your hazard classification from light to ordinary 1 for whatever reason,

1. Water required will be higher (0.15 GPM/sqft instead of 0.10 GPM/sqft)
2. Coverage per sprinkler will be less (130 sqft/sprinkler instead of 225 sqft/sprinkler)

So basically, there's additional cost for piping, fittings, sprinklers, and pump capacity.

But whatever your reason is, we won't understand unless you tell us.

 

[fpst]

I still want a water sprinkler system
I'm aware that it is more costly - however, certain construction features would not be possible if you could not do this. For example, light hazard beneath drop-out ceiling tiles. NFPA 13 says you can't install quick response sprinklers above drop-out ceiling tiles. It also says quick response sprinklers must be installed in light hazard occupancies.

A designer may tell an architect "it can't be done" but the truth may be that the designer simply didn't consider the option of increasing the light hazard occupancy to ordinary 1 to make it work. Yes, it's more costly, as many architectural features end up being, but it's possible. This would not be true if you can't arbitrarily increase the hazard like this. Hence the question.

 

[MatthewJWillis]

No.

I take a lesson from Lincoln when asked this very question.

"If you call a dog's tail a leg, then how many legs does the dog now have?"
The answer is 4. Simply calling it a leg does not make it one.

The QR is there for a reason. Getting the water out fast is far more important than getting a lot more out at a later time.
And remember, the sprinkler system is just one part of the fire protection picture.
Bottom line is it will be far more expensive up front, and possibly exponentially so if you have to defend after a fire as to why you did not meet code minimum...

R/
Matt

 

[MatthewJWillis]

I kind of guessed this was where you were heading.
I have a question about that myself.
WHY isn't QR allowed above? The ceiling will bank the heat and take the first hit. Since QR is so effective, why do we not want them above?


R/
Matt

 

[ZDR1985]

If it is the option then YES it can be done, I don't know any code that prohibits doing it.

Actually this is done in some restaurants where the dining area is light hazard and kitchen is ordinary hazard. Also, in a building where most part is ordinary hazard and little part is light hazard. So it is better going for higher hazard in case of worst case scenarios.

 

[fpst]

Your first reply is not what I would have expected. I was under the impression that, for example, if you have a room protected as ordinary 1, and later convert it to light hazard, you were okay - no sprinkler retrofit was required, since at the time of installation the hydraulics for the ordinary 1 system should have worked in that room, therefore being more than enough for light hazard uses.

But what you're saying seems to be that light hazard materials require faster water discharge?

 

[MatthewJWillis]

Correct. And if it does change to office, then that is a re-design occupancy change.

Light hazard fires have less to burn. Therefore there are lower rates of heat release. This is where the R.T.I. of 55( I think) or less is important.
Ordinary occupancies put off more heat. Read the base definitions in chapter 3 again using this thought process.

R/
Matt

 

[TravisMack]

I think you can obviously raise the density, but you still have to meet the requirements of the original hazard. There is nothing that prohibits one from designing a light hazard area to 0.15 / 1500. However, there are things that prohibit one from using SR sprinklers in a light hazard area.

What's in a name? An office by any other name is still just an office. Yeah, that was my bad attempt at paraphrasing Shakespeare to make a point.

I believe I know the question that brought this up. In that situation, the builder wanted to use drop out tiles to save putting pendent sprinklers in the ceiling since the shell space was already protected. However, as in most cases, when non-experienced individuals try their hand at fire protection work, they often miss many of the nuances of our industry.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[stookeyfpe]

Don't forget that in certain jurisdictions, the model fire code may have a specific requirement that supersedes a particular requirement in a NFPA standard. For example, the 2003, 2006, 2009 & 2012 IFC in Section 903.3.2 requires QR in all Light Hazard occupancies and in smoke compartments within Institutional occupancies where patients are incapable of self preservation. You should consider reviewing your particular case with the approving authority.