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Small closets in office buildings

Small closets in office buildings

Small closets in office buildings

Greetings everyone. I'm new at the fire protection design world so I have a few basic questions still unanswered, so please bear with me. I have a small medical office (950 sq. ft.)with a few small storage areas. The biggest one measures 17 sq. ft. I also have a janitor closet and a hazardous waste (non-flammable) closet which measure a measly 5 sq. ft. each.

According to NFPA 13, medical offices are considered light hazard. However, storage areas are considered OH-1.

So, my question is how should I proceed with the hydraulic calculation? Should I use the 0.15 gpm/sq.ft. density over the entire area; or just for the closets and use 0.10 gpm/sq.ft. for everything else? The closets are not divided by slab to slab walls, the dividing walls only reach up to the acoustic ceiling.

Thanks in advance!

RE: Small closets in office buildings

The presence of a janitor's closet in an office building does not make the entire building a OH1 calc.  Just be sure to flow the heads at the proper density for the room where the head is located: 0.10 for light hazard and 0.15 for OH1.  You can be extra conservative and include 250 gpm for the hose if you want.

Travis Mack
MFP Design, LLC

RE: Small closets in office buildings

If you do the math, I think you will find the sprinklers in the janitors closets are far in excess of the 0.15 density when operating at the minimum 7 psi. This is usually the case when storage closets are considered from my experience.

You could probably also ignore it altogether since you won't be taking a remote area reduction for ceiling height and qr sprinklers given the entire building is less than the standard remote area. 13 allows the omission of calculated sprinklers in closets under certain conditions.

RE: Small closets in office buildings

Just a thought,

the general storage rules in NFPA 13 state that OH1 can protect Clkass I and Class II Commodities.  It says nothing about Class III or Class IV or Group A Plastics.  These fall under OH2.

May seem to be picking nits, but I find it difficult to believe that these closets, no matter how big or small, will have absolutley no Class III or Class IV or Group A Plastics at all.  

These should be OH2 in my opinion.

Fire Sprinklers Save Lives.
Can You Live Without Them?

RE: Small closets in office buildings

Really firepe?

Glad you're not my AHJ.  You don't have to go into storage rules for a closet.  With your logic every occupancy would have to be protected to OH2.

R M Arsenault Engineering Inc.

RE: Small closets in office buildings

I recommend reading all of the NFPA 13 section on calculations, and get the handbook version of 13 if possible. If you can, purchase this book:

     " 'Layout, Detail and Calculation of Fire Sprinkler Systems' (2nd Edition) - This newly revised hardcover textbook has been updated to reference the 2007 and 2010 editions of NFPA 13 with more examples and student exercises and new chapters on contract issues and stocklisting. This text remains the most complete book ever written for the fire sprinkler engineering technician. "

I have no affiliation with NFSA, but it is a well written book.  If you are teaching yourself you really need to read, read, read and have good reference materials.. It is well worth the money unless you are in a developing country where $195 is a week or two of pay.

Re: the OH2 for storage rooms.

I am an AHJ/plan reviewer and require OH2 for storage rooms that will be mainly storing paper files, cardboard, etc.  (example: medical records).

I cite the miscellaneous storage language from 13; paper and cardboard are class III commodities.  A room dedicated to their storage is misc storage. The miscellaneous storage of Cl.III commodities is OH2, plain as day..

I went to a sprinkler design class once where this came up, and we discussed this issue at length. These were highly experienced folks.  Half the class agreed with OH2, the other said they design to OH1 essentially because that is 'how they always do it'.

Btw that is the one thing you should never ever say to an AHJ;  Don't say, "I've done 35 buildings across the county this way and they were all accepted."  It seems logical to say to make a point, but it is like nails on a chalkboard and makes our stomach turn.. Any AHJ will tell you that, at least the ones I have met since getting this gig.  Always cite the section from the standard and how the design meets the wording.  Leave feelings out of it, use written terminology.


Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.  

RE: Small closets in office buildings

Thanks everyone for your comments.

Pipesnpumps I will check out the book you're recommending. So basically, according to what you are explaining, there will be three classifications here, light hazard for the office area, class I commodity for the hazardous waste closet, and a class III commodity for the records storage. Since the HMD sprinkler is located in an office, the hydraulic calculation should consider the 0.10 gpm/sq.ft. all the way to the closets and then just add the corresponding gpm per density (0.15/0.20) for the commodities classified as OH-1 & OH-2?

RE: Small closets in office buildings

pipesnpumps, I don't mean to be a thorn in you side but just for clarity regarding your comment(s):

"...storage rooms that will be mainly storing paper files, cardboard, etc.....A room dedicated to their storage is misc storage. The miscellaneous storage of Cl.III commodities is OH2, plain as day.."

What you are describing is actually OH1. Ordinary hazard (Group 1) occupancies shall be defined as occupancies or portions of occupancies where combustiblity is low, quantity of combustibles is moderate, STOCKPILES OF COMBUSTIBLES DO NOT EXCEED 8 FT, and fires with moderate rates of heat release are expected.

A.5.3 For purposes of thes defintions, Class I, Class II, Class III and Class IV commodities would be considered to have moderate rates of heat release....

So unless your office supply storage room has paper and cardboard storage exceeding 8ft in height, then the room is stockpipe ancilliary to the primary occupancy, is considered OH1 and need not be protected to miscellaneous storage criteria.

If a library stack area can be light hazard then most certianly a paper storage closet could be OH1 at worst.

R M Arsenault Engineering Inc.

RE: Small closets in office buildings

Yes I agree that some shelving incidental to a LH is allowed to be protected by LH...   The rub is when does it become misc storage?   the line is NOT clear, but if the storage room is of any significant size I submit that meets the definition of misc storage, read below:

NFPA 13 - 2010:
"* Miscellaneous Storage. Storage that does not exceed 12 ft (3.66 m) in height and is incidental to another occupancy use group.

Such storage shall not constitute more than 10 percent of the building area or 4000 ft2 (372 m2) of the sprinklered area, whichever is greater. Such storage shall not exceed 1000 ft2 (93m2) in one pile or area, and each such pile or area shall be separated from other storage areas by at least 25 ft (7.62 m)."

Note that A. states "these requirements apply for all storage of 12 ft or less in height..  

Bottom line, the IBC occupancy has no bearing on the NFPA terminology for storage.

As for libraries, they are on solid usually metal shelves, they are normally packed tight, and neat, and is not the same type of fire hazard.  It is a question of risk.   More risk in a cluttered back storage room full of old files and who knows what, means higher density, according to how /I/ read the above passages.     As i tell people you will need to add one or two heads.   I dont see any reason to fight it, particularly in a sizeable storage room.

Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.  

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