Required fire flow

[Inspector 102]

If calculating the required fire flow for the following fire, which formula would be used?

Single story storage building is 75 x 100 feet with exposure on 2 sides. the building is 75% involved.

75x100=7500/3=2500 x 75% = 1875 + 25% for each exposure (x2) = 1250 = required fire flow of 3125 GPM, or

75x100=7500/3=2500 x 75% = 1875 + 25% of 1875 for each exposure (x2) = 937.5 gpm = 1875 + 938 = 2813 GPM

This was a sample question on a test which raised all kinds of arguement. Although only 300 GPM difference, when it comes to test questions, you know how picky they can be.

I calculate LxW/3 = NFF @ 100% / 25% x %involvement + 25% for each exposure which is the first formula. They say that is wrong based on Fire Officer Strategy and Tactics handbook. I am not sure whether I learned this from Vincent Dunn or Brunocenni, but I am sure this is the way I alway calculated. Any comments on which method is correct?

 

[Builder Bob]

75x100=7500/3=2500 x 75% = 1875 + 25% of 1875 for each exposure (x2) = 937.5 gpm = 1875 + 938 = 2813 GPM

Would be the correct way to use this fire flow method.

1875 + (1875 *25%) +(1875*25%)

While I don't necessarily agree with this method, That is the way it was always taught to me..... (Back when Fred and Barney were the first hook and ladder driver and officer)

 

[Inspector 102]

Thanks BB, That is the way the state determines also. I am not sure where I came up with the other method. Either will work on the fire ground. Took the state exam last night for Fire Officer Strategy and Tactics. That question did not even appear on my test. Normally around here, more fire means more water. That is all we need to know.

 

[sdpaddler50]

View attachment 1479You guys are speaking in greek to me. The Civil Engr usually does fire flows for on site hydrants, so its not something i have dealt much with. Cal Fire Code, Table BB105.1 is attached. I assume this is similar to the IFC. What reference, tables did you use to calculate? just curious. Thanks.

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[Builder Bob]

sppaddler50 - The fire flow discussion is about fire ground strategy and tactics, The fire service has about 4 or five different ways to determine fire flows...... IOWA, NFA, ISO, IFC, etc. etc. etc.

The fire flow questions are usually used to determine if a fire officer has the ability to perform math functions and determine if he/she has the adequate resources on hand to put the required fire flow on said scenario.

The fire flow determination from the IFC is geared towards seeing if the infrastructure (existing or designed) will support the type of construction proposed. (different application)

I hope this helps clarify the question that you had...

 

[sdpaddler50]

Thanks for clarifying Bob.