B occupancy vs S-1 or S-2

[nealderidder]

Consider a single story building with 20,000 SF of B occupancy and 10,000 of an S occupancy (this is all hypothetical). If the S occupancy were classified as an S-1 and stored rolls of paper, no fire separation would be required between the B and S.

If the S occupancy were classified as an S-2 (lower hazard than S-1) and stored cans of beans, a one hour separation would be required between the B and S.

Why would I need to protect the B from the Beans but not from the paper? Or is it the other way around and I need to protect the Beans from the hazards in the B occupancy? On the surface it doesn't seem logical to add a separation requirement when I go to less hazardous storage. I'm guessing I'm missing something obvious?

 

[Yankee Chronicler]

You are not missing anything, you just haven't accepted it.

A long time ago, an instructor at a class I attended describe low-hazard storage as storing iron ingots in steel pails filled with water. His point was that most storage occupancies will be moderate hazard. Per the table for occupancy separations, moderate hazard storage is viewed by the code as being equal in fire hazard to business occupancies.

Since low-hazard storage is, by definition as well as by code, a lower hazard than moderate-hazard, then low-hazard storage must necessarily be less hazardous than a business occupancy. So you guess it -- the separation isn't to protect the B occupancy from the S-2 occupancy, it's to protect the S-2 from the B.

 

[nealderidder]

You are not missing anything, you just haven't accepted it.

A long time ago, an instructor at a class I attended describe low-hazard storage as storing iron ingots in steel pails filled with water. His point was that most storage occupancies will be moderate hazard. Per the table for occupancy separations, moderate hazard storage is viewed by the code as being equal in fire hazard to business occupancies.

Since low-hazard storage is, by definition as well as by code, a lower hazard than moderate-hazard, then low-hazard storage must necessarily be less hazardous than a business occupancy. So you guess it -- the separation isn't to protect the B occupancy from the S-2 occupancy, it's to protect the S-2 from the B.

Makes sense really. I just have it in my head that storage is more hazardous than business... I'm sure the Fire Dept. would be happy if we only stored iron in pails of water : ) There is a long list of low-hazard items listed in 311.3 other than that but I get your point. Thanks for the reply.

 

[steveray]

The cans of beans may explode if on fire....H3.....lol

 

[ScottEricT]

Thank you Yankee for shedding light on S-1, S-2, B hazard relationship.

Per IBC 508.3, any reason this could not be approached as 'Nonseparated Occupancies?' Assuming single story for the building, Type VB (sprinklered), Table 506.2 allows 36,000 sqft for the 'B' floor area, and 54,000 sqft for the S-2 floor area. 36,000 sqft is the more restrictive.

In the scenario, B + S-2 floor area = 20,000 sqft + 10,000 sqft = 30,000 sqft < 36,000 sqft, therefore OK.

Any issues with this approach?

 

[steveray]

Thank you Yankee for shedding light on S-1, S-2, B hazard relationship.

Per IBC 508.3, any reason this could not be approached as 'Nonseparated Occupancies?' Assuming single story for the building, Type VB (sprinklered), Table 506.2 allows 36,000 sqft for the 'B' floor area, and 54,000 sqft for the S-2 floor area. 36,000 sqft is the more restrictive.

In the scenario, B + S-2 floor area = 20,000 sqft + 10,000 sqft = 30,000 sqft < 36,000 sqft, therefore OK.

Any issues with this approach?

No....but IF a commodity change goes to S1 you would be sprinklering the building.....

 

[ScottEricT]

Sorry, I don't follow the logic. With the B+S-2, non-separated, it would need to be Type VB Sprinklered already.
Is there another piece to the puzzle I'm missing?
I suppose other construction types would allow the B+S-2 to be non-sprinklered, but B+S-1 to be sprinklered.

 

[Mr. Inspector]

They need to be separated because the B area has a higher occupancy and if they all ate the beans it could be a fire hazard because of all the methane.

 

[steveray]

Sorry, I don't follow the logic. With the B+S-2, non-separated, it would need to be Type VB Sprinklered already.
Is there another piece to the puzzle I'm missing?
I suppose other construction types would allow the B+S-2 to be non-sprinklered, but B+S-1 to be sprinklered.

Sorry, I did not look at the H&A table...and missed your parenthetical.....More of a general note that a commodity shift in an S2 can have huge consequences....

 

[Yankee Chronicler]

Sorry, I did not look at the H&A table...and missed your parenthetical.....More of a general note that a commodity shift in an S2 can have huge consequences....

Back to the comment we received in that class years ago about S-2 basically meaning the storage of iron ingots in steel pails filled with water. The instructor's point was that S-2 is LOW-hazard storage, intended for storing items that inherently offer both little risk of catching fire, AND offer a comparatively low combustible fuel load.

 

[steveray]

Back to the comment we received in that class years ago about S-2 basically meaning the storage of iron ingots in steel pails filled with water. The instructor's point was that S-2 is LOW-hazard storage, intended for storing items that inherently offer both little risk of catching fire, AND offer a comparatively low combustible fuel load.

Correct...it is rarely S2.....