// CODE SNIPPET

# 701.4 Indoor Combustion Air

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The required volume of
indoor air shall be determined in accordance with the method
in Section 701.4.1 or Section 701.4.2, except that where the
air infiltration rate is known to be less than 0.40 ACH (air
change per hour), the method in Section 701.4.2 shall be used.
The total required volume shall be the sum of the required
volume calculated for appliances located within the space.
Rooms communicating directly with the space in which the
appliances are installed through openings not furnished with
doors, and through combustion air openings sized and located
in accordance with Section 701.5, are considered a part of the
required volume. [NFPA 54:9.3.2]

The required volume shall
be not less than 50 cubic feet per 1000 British thermal
units per hour (Btu/h) (4.83 m

^{3}/kW). [NFPA 54:9.3.2.1]Where
the air infiltration rate of a structure is known, the minimum
required volume shall be determined as follows
[NFPA 54:9.3.2.2]:

- For appliances other than fan-assisted, calculate using the following Equation 701.4.2(1). [NFPA 54:9.3.2.2(1)]
- For fan-assisted appliances, calculate using the following Equation 701.4.2(2). [NFPA 54: 9.3.2.2(2)]
- For purposes of these calculations, an infiltration rate greater than 0.60 ACH shall not be used in the equations in Section 701.4.2(1) and Section 701.4.2(2). [NFPA 54:9. 3.2.2(3)]

Required Volume

_{other}≥ (21 ft^{3}/*ACH*) x (*I*/1000 Btu/h)_{other}**[Equation 701.4.2(1)]**
Required Volume

_{fan}≥ (15 ft^{3}/*ACH*) x (*I*/1000 Btu/h)_{fan}**[Equation 701.4.2(2)]**Where: | ||

I _{other} |
= | All appliances other than fan-assisted input (Btu/h) |

I _{fan} |
= | Fan-assisted appliance input (Btu/h) |

ACH | = | Air change per hour (percent of volume of space exchanged per hour, expressed as a decimal) |

For SI units: 1 cubic foot = 0.0283 m^{3}, 1000 British thermal units per
hour = 0.293 kW |

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