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403.3.1.1.2.3.4 Outdoor air intake flow rate.
The outdoor air intake flow rate (V
ot
) shall be determined in accordance with Equation 4-8.
V
ot
= V
ou
/ E
v | (Equation 4-8) |
403.3.1.2 Short-term conditions.
If it is known that peak occupancy will be of short duration and/or ventilation will be varied or interrupted for a short period of time, the design may be based on the average conditions over a time period T determined by Equation 4-9.
T = 3V / Vbz | (Equation 4-9) (US) |
T = 50V / Vbz | (Equation 4-9) (SI) |
where:
T | = | averaging time period, minutes |
V | = | the volume of the zone of which averaging is being applied, cubic feet |
Vbz | = | the breathing zone outdoor airflow calculated using equation 4-1 and design valve of the zone population Pz, cfm |
Acceptable design adjustments based on this optional provision include the following:
1. Zone with fluctuating occupancy: the zone population (Pz) may be averaged over time T.
2. Zone with intermittent interruption of supply air: the average outdoor airflow supplied to breathing zone over time T shall be no less than the breathing zone outdoor airflow (Vbz) calculated using Equation 4-1.
3. A system with intermittent closure of outdoor air intake: the average outdoor air intake over time T shall be no less than the minimum outdoor air intake (V
ot
) calculated using Equation 4-3, 4-4 or 4-8 as appropriate.
403.3.1.3 Exhaust ventilation.
Exhaust airflow rate shall be provided in accordance with the requirements of Table 403.3.1.1. Exhaust makeup air shall be permitted to be any combination of outdoor air, recirculated air and transfer air, except as limited in accordance with Section 403.2.
403.3.1.4 System operation.
The minimum flow rate of outdoor air that the ventilation system must be capable of supplying during its operation shall be permitted to be based on the rate per person indicated in Table 403.3.1.1 and the actual number of occupants present.
403.3.1.5 Variable air volume system control.
Variable air volume air distribution systems, other than those designed to supply only 100-percent outdoor air, shall be provided with controls to regulate the flow of outdoor air. Such control system shall be designed to maintain the flow rate of outdoor air at a rate of not less than that required by Section 403.3.1.1 over the entire range of supply air operating rates.
403.3.1.6 Balancing.
The ventilation air distribution system shall be provided with means to adjust the system to achieve not less than the minimum ventilation airflow rate as required by Sections 403.3.1.1 and 403.3.1.2. Ventilation systems shall be balanced by an approved method. Such balancing shall verify that the ventilation system is capable of supplying and exhausting the airflow rates required by Sections 403.3.1.1 and 403.3.1.2.
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