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- To calculate people outdoor airflow rate in breathing zone update#
Occupancy sensors, which detect the presence or number of people in a zone.ĬO 2 sensors, which monitor the amount of CO 2 produced by occupants and diluted by outdoor air. Occupancy schedules, by which a building-automation system (BAS) predicts population based on time of day. Ventilation demand can be assessed one of three ways: This control strategy-DCV-responds to the actual need, or "demand," for ventilation by regulating the rate at which an HVAC system brings outdoor air into a building. Standard 62.1 allows the resetting of intake airflow in response to changes in zone population. The standard lists three types of dynamic reset: In Section 6.2.7, "Dynamic Reset," Standard 62.1 permits an HVAC system to "reset the design outdoor-air intake flow (Vot) and/or space or zone airflow as operating conditions change." Although the standard does not provide details for implementation, any system-control approach that responds to varying conditions must be capable of providing at least the required minimum breathing-zone outdoor airflow whenever the zones served by a system are occupied. This article reviews Standard 62.1's requirements for dynamic reset and outlines several methods of implementing DCV using CO 2 sensors. The good news is that DCV remains do-able and practical, especially for spaces such as gymnasiums and meeting rooms, where people and their activities are the main sources of contaminants. But implementing DCV based on indoor levels of carbon dioxide (CO 2) is not as straightforward under the 2007 version of ANSI (American National Standards Institute)/ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) Standard 62.1, Ventilation for Acceptable Indoor Air Quality, as it was under previous versions.
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5) edition of Engineers Newsletter, "CO 2-Based Demand-Controlled Ventilation With ASHRAE Standard 62.1-2004." Published periodically by Trane's Applications Engineering group, Engineers Newsletter is intended to aid engineering professionals in the design and application of HVAC systems by providing "reliable, objective, and technologically current information in a non-commercial format." Engineers News-letter is archived at Demand-controlled ventilation (DCV) can reduce the cost of operating an HVAC system.
To calculate people outdoor airflow rate in breathing zone update#
However, when this flow is combined with local source control the exposure may paradoxically increase, depending on the airflow interaction at the breathing zone and the source location.Editor's note: Following is an update of the November 2005 (Volume 34, No. Airflow imposed against the face can substantially reduce the exposure regardless of the pollution source location. Local pollution source control by exhaust ventilation integrated into the seat reduced the exposure. Breathing did not influence the exposure to gaseous pollutants emitted from the lower part of the body, in this case, the groin. The exposure in the case of exhalation through the nose was higher than when exhalation took place through the mouth. It was found that the flow of exhalation substantially affected the exposure to dermally-emitted bio-effluents released close to the breathing flow, e.g. Bio-effluents released at the armpits and groin were simulated with two tracer gases.
To calculate people outdoor airflow rate in breathing zone full size#
A breathing thermal manikin was used to simulate a seated person in a full size climate chamber. The influence of the complex interaction of three airflows - breathing flow, convective flow around the human body and ventilation flow directed against the face - on the exposure to dermally-emitted effluents from a person's own body was examined together with the effects of source location and control.