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Ventilation Rate

Minimum outdoor airflow of a space by the ventilation rate procedure of ASHRAE Standard 62.1: the breathing-zone rate is the people component Rp times the occupants plus the area component Ra times the floor area, with Rp and Ra from the standard's table for the occupancy category; dividing by the zone air-distribution effectiveness of the supply arrangement gives the outdoor air the system must deliver to the zone. The tool lists the category rates, reports the breathing-zone and zone outdoor airflows, the rate per person and per unit area, and the outdoor-air fraction of a given supply airflow.

  • Rp and Ra for the common occupancy categories of ASHRAE 62.1 Table 6-1, or entered

  • Breathing-zone outdoor airflow Vbz = Rp Pz + Ra Az

  • Zone outdoor airflow Voz = Vbz / Ez with the air-distribution effectiveness

  • Outdoor-air fraction of the supply airflow; per-person and per-area rates

Ventilation Rate

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ASHRAE 62.1 Ventilation Rate Procedure | Method page
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Ventilation Rate

ASHRAE 62.1 Ventilation Rate Procedure

Standard 62.1 sets the minimum outdoor air a space needs for acceptable indoor air quality as two parts: a people component that dilutes the contaminants occupants produce, Rp per person, and an area component for what the building and its furnishings emit, Ra per unit of floor area. The breathing-zone outdoor airflow is Vbz = Rp Pz + Ra Az. The rates come from the standard's Table 6-1 by occupancy category; the rows offered here are the common ones, and any category can be entered.

Not all the air delivered to a zone reaches the breathing zone. The zone air-distribution effectiveness Ez of Table 6-2 credits or penalizes the supply arrangement: 1.0 for cool air from the ceiling, 0.8 for warm air from the ceiling that short-circuits to a ceiling return, 1.2 for displacement ventilation from the floor. The zone outdoor airflow the system must deliver is Voz = Vbz / Ez.

For a single-zone system that is the outdoor-air intake. A multiple-zone recirculating system serves zones with different outdoor-air fractions Zp = Voz / Vpz, and the system intake follows from the critical zone by the standard's Appendix A; the tool reports Zp for the entered supply airflow as the input to that step. Local codes may adopt an earlier edition of the standard or different rates.



References

American Society of Heating, Refrigerating and Air-Conditioning Engineers (2022). ANSI/ASHRAE Standard 62.1-2022: Ventilation and Acceptable Indoor Air Quality. ASHRAE, Peachtree Corners, GA.

American Society of Heating, Refrigerating and Air-Conditioning Engineers (2021). ASHRAE Handbook: Fundamentals. ASHRAE, Peachtree Corners, GA.

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