Based on ASHRAE’s efforts to make the IAQP more prescriptive, now it is possible to select outdoor airflow and air cleaner volume for a passing design via a table (like the VRP). ASHRAE enables this through Standard 62.1 contaminant limits, contaminant generation rates, and an air cleaner validation process. Therefore, the only variable is selecting outdoor air pollution levels. Applying worst-case annual average outdoor air concentrations from North American cities into ASHRAE’s calculator, a table can be built to match the ease of the VRP.
IAQP parameters for each occupancy category in the Minimum Ventilation Rates Table were iteratively proven and documented in the updated table. Designers need to calculate two values to complete an IAQP design: minimum ventilation (Vbz) and air cleaner capacity (Vc). The process to calculate is straight forward and defined in the steps below.
Standard 62.1 §6.2.1.1. Outdoor Airflow - IAQP:
The rate of outdoor airflow in the occupied space shall be not less than the following:
Vbz ≥QP x PZ
where: QP = flow rate of outdoor air required per person from the Clean Air Ventilation Table. PZ = zone population, the number of people in the ventilation zone.
Compliant air cleaner minimum airflow shall be determined with the following:
Vc ≥CR x AZ
where: CR = airflow flow rate of a compliant air cleaner AZ = zone floor area, net occupied floor area of the ventilation zone
The design requires outdoor airflow ≥ Vbz and ≥ Vc as calculated. Follow 62.1 or zone and/or system ventilation efficiency corrections in selecting total outdoor airflow.
Compliant Air Cleaning Rating
The air cleaner must have filtration efficiency exceeding the following per 62.1-2022 Addenda N & AA or 62.1-2025 §6.3.4:
Documentation of the IAQP on submitted plans may require using the smartIAQ IAQP Calculator.
Example 1
IAQP design for a classroom (age 9 plus), with a 900ft2 classroom, default occupancy (35/1,000ft2). In this case Pz = (35/1,000) * 900 = 32 people.
From the table: QP = 5 CFM, CR = 0.10
Vbz ≥ QP x PZ, Vbz ≥ 5 CFM * 32 Vbz ≥ 160 CFM
Vc ≥ QP x PZ, Vc ≥ 0.10 * 900 Vc ≥ 90 CFM
A 900 ft2 classroom with a ventilation rate of 160 CFM and 90 CFM of air cleaning (with the cleaning performance listed above) will pass the IAQP.
Example 2
IAQP design for a place of religious worship, with a 4,000ft2 space, default occupancy (120/1,000ft2). In this case Pz = (120/1,000) * 4,000= 480 people.
From the table: QP = 4 CFM, CR = 0.20
Vbz ≥ QP x PZ, Vbz ≥ 4 CFM * 480 Vbz ≥ 1,920 CFM
Vc ≥ QP x PZ, Vc ≥ 0.20 * 4,000 Vc ≥ 800 CFM
A 4,000 ft2 place of religious worship with a ventilation rate of 1,920 CFM and 800 CFM of air cleaning (with the cleaning performance listed above) will pass the IAQP.
