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Stair Pressurization Estimator
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Disclaimer: This calculator is for estimating purposes only and
is not for final design calculations. This does not take the place of a
rational analysis and does not incorporate all factors that could impact
stair pressurization. Consult a licensed fire protection engineer.
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Description
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Value
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Unit
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Building Inputs
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Number of Stories
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Stories
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Average Floor Height
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Feet
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Average Building Perimeter per
Floor
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Feet
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Number of Stairways
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Stairs
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Stair Length
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Feet
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Stair Width
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Feet
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Total Length of Stair Wall
Bordering Inside
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Feet
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Total Length of Stair Wall
Bordering Outside
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Feet
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Number of Doors Between Stair
and Building
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Doors
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Number of Doors Between Stair and Outside
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Doors
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Model Inputs
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Max Pressure Difference
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0.35
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in. H20
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Min Pressure Difference
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in. H20
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Construction
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-
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Outdoor Design Temp - Summer
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F
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Outdoor Design Temp - Winter
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F
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Summary
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Required Flow Rate - Summer
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CFM
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Required Flow Rate - Winter
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CFM
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Assumptions:
All equations, calculations from Handbook of Smoke Control Engineering, 2nd
Edition, Klote
All stairs are uniform in dimension
All stair doors closed
Building/stair temperature is 70F
Atmospheric pressure is 14.7 psi
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Parameter
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Abbreviation
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Value
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Unit
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Area Between Stair and
Building
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ASB
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SF
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Area Between Building and
Outside
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ABO
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SF
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Area Between Stair and Outside
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ASOu
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SF
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Area Between Stair and Roof
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ASOr
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SF
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Winter
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Outdoor Air Density
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ρo
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lb./ft3
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Temperature Factor
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FT
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in. H2O/ft
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Flow Area Factor
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FR
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-
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Pressure Difference between
Stair and Building, top
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PSBt
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in. H2O
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Pressure Difference between
Stair and Building, bottom
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PSBb
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in. H2O
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Pressure Difference between
Stair and Building, average
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PSBav
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in. H2O
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Pressure Difference between
Stair and Outside, bottom
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PSOb
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in. H2O
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Pressure Difference between
Stair and Outside, top
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PSOt
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in. H2O
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Pressure Difference between
Stair and Outside, average
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PSOav
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in. H2O
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Mass Flow Rate between Stair
and Building
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mSB
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lb/s
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Mass Flow Rate between Stair
and Outside, wall leaks
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mSOu
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lb/s
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Mass Flow Rate between Stair
and Outside, door
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mSOd
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lb/s
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Mass Flow Rate between Stair
and Outside, roof
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mSOr
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lb/s
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Total Mass Flow Rate
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m
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lb/s
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Total Volumetric Flow Rate
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V
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CFM
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Summer
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Outdoor Air Density
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ρo
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lb./ft3
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Temperature Factor
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FT
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in. H2O/ft
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Flow Area Factor
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FR
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-
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Pressure Difference between
Stair and Building, top
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PSBt
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in. H2O
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Pressure Difference between
Stair and Building, bottom
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PSBb
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in. H2O
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Pressure Difference between
Stair and Building, average
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PSBav
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in. H2O
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Pressure Difference between
Stair and Outside, bottom
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PSOb
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in. H2O
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Pressure Difference between
Stair and Outside, top
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PSOt
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in. H2O
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Pressure Difference between
Stair and Outside, average
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PSOav
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in. H2O
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Mass Flow Rate between Stair
and Building
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mSB
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lb/s
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Mass Flow Rate between Stair
and Outside, wall leaks
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mSOu
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lb/s
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Mass Flow Rate between Stair
and Outside, door
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mSOd
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lb/s
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Mass Flow Rate between Stair
and Outside, roof
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mSOr
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lb/s
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Total Mass Flow Rate
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m
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lb/s
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Total Volumetric Flow Rate
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V
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CFM
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