![]() R = Rate, standard cubic feet per minute of air per person N = CO 2-generation rate, standard cubic feet per minute of CO 2 per personĬi = Inside CO 2 concentration, standard cubic feet per minute of CO 2 per cubic feet per minute of air Vo = Outdoor-airflow rate, standard cubic feet per minute of air Indoor CO 2 level is used to estimate outdoor-airflow rate per person based on a steady-state relationship ( Figure 1), which can be applied to single-zone systems.Ĭo = Outdoor-air CO 2 concentration, standard cubic feet per minute of CO 2 per cubic feet per minute of air DCV should not be considered for low-occupant-density spaces because the uncertainty of most DCV techniques is too great and the potential benefit too meager for practical application. Most standards and rating systems (American Society of Heating, Refrigerating and Air-Conditioning Engineers Title 24, Part 6, of the California Code of Regulations Leadership in Energy and Environmental Design ) consider high occupant density to be 25 or more people per 1,000 sq ft. Generally, DCV should be considered only for high-occupant-density spaces with potential for significant changes in population density. This article will clarify the relationship between CO 2 level and ventilation rate and offer suggestions for improving traditional single-setpoint CO 2 DCV through the addition of a direct outdoor-airflow-measuring device. Unfortunately, many designers do not have a clear understanding of the relationship between CO 2 and ventilation and the requirements for proper ventilation control. ![]() ![]() According to one method of DCV, ventilation rate is adjusted based on carbon-dioxide (CO 2) level. For some spaces, demand-controlled ventilation (DCV) based on changes in occupancy may be desirable. Reducing the amount of outdoor air entering a space when an HVAC system is mechanically cooling or heating and an air-side economizer is inactive has distinct advantages. ![]()
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