If both sources are present and both (for example) produce perceivable odors, then the ventilation rate required for adequate dilution is the sum of the rates needed to handle each source separately. Sources originating from the building and its furnishings: response in cfm/sf.Sources originating from occupants and their activities: response in cfm/person. This is because ASHRAE considers two types of contaminant sources, either of which may be present in an indoor environment: offices, museums, supermarkets, and so on). Next, let’s define the ventilation rate. ASHRAE Standard 62.1 specifies ventilation rates based on cubic feet per minute (cfm) per person and per square foot of floor area – and both are related to the occupancy type (e.g. Ventilation Rate (Combined Outdoor Air Rate) The breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. For this reason, we should consider the minimum ventilation rate within the “breathing zone.”ĪSHRAE defines the breathing zone as follows: Ventilation air only benefits occupants if it reaches them. The standard specifies minimum ventilation rates and other measures for both new and existing buildings that are intended to foster a level of indoor air quality that is acceptable to occupants and mitigates adverse health effects. When it comes to defining minimum ventilation rates in buildings (except for low-rise residential), the premiere reference is ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality. Yet, a basic question that commonly emerges is simply: How much ventilation should I provide in a building? ANSI/ASHRAE Standard 62.1 Ventilation rates in our buildings can be a complicated subject and there is no shortage on ways to assess how air is brought into an indoor environment. Originally published on Novemby BNP Media through the Building Enclosure Blog.
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