![]() ![]() This article does not examine the prescriptive formulas accounting for multiple-zone systems, zone air-distribution effectiveness, or zone primary outdoor airflow fractions. Note that this article focuses on the calculation of uncorrected outdoor airflow values as generally defined in ASHRAE 62.1-2016 Section 6.2.5.3. ![]() In simple terms, find the maximum occupants in each space, find the areas of each space, calculate the breathing-zone outdoor airflows, and then add them up. For a dedicated outdoor-air single-zone system, summing up the ventilation requirements for each zone results in the total possible uncorrected outdoor-air intake value. The breathing-zone outdoor airflow (Vbz) is calculated by summing the people ventilation requirements and the area ventilation requirements for the space (ASHRAE 62.1-2016 Section 6.2.2.1). Refer to the ASHRAE 62.1-2016 Table 6.2.2.1, Minimum Ventilation Rates in Breathing Zone for the specific per-person airflow rates (R p) and per-square-foot airflow rates (R a) based upon the use of the space. ![]() Those requirements that are due to the zone area/square footage of the spaces (Az) are calculated at a different rate, the "area rate" (R a), in cubic feet per minute per square foot. Outdoor-air requirement rates of airflow ("R") due to occupants ("p" for population or people) are calculated at one rate, the "per person rate" (R p) in cubic feet per minute per person based upon the design-zone population (P z). That’s on top of air contamination that comes from paint, carpet, upholstery, and other fixtures that emit minute particles and vapors, all of which are already figured into the mathematic formulas found in ASHRAE 62.1-2016, the standard that regulates outdoor air. People that occupy a room will contaminate indoor air by exhaling carbon dioxide, sweating, coughing, etc. ![]()
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