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Air changes per hour is a measurement intended to communicate the air change effectiveness of a space’s ventilation system. Discussion around the ASHRAE standard 62, Ventilation for Acceptable Indoor Air Quality led to the development of a more direct method of measuring air change effectiveness with the use of a tracer gas. [1]
A normal minute volume while resting is about 5–8 liters per minute in humans. [1] Minute volume generally decreases when at rest, and increases with exercise. For example, during light activities minute volume may be around 12 litres. Riding a bicycle increases minute ventilation by a factor of 2 to 4 depending on the level of exercise involved.
The efficiency is a function of the total losses in the fan system, including aerodynamic losses in the fan, friction losses in the drive (e.g. belt), losses in the electric motor, and variable speed drive power electronics. For more insight into how to maximise energy efficiency and minimize noise in fan systems, see ref.1
Ventilation on the downdraught system, by impulsion, or the 'plenum' principle, applied to schoolrooms (1899) Natural ventilation is the ventilation of a building with outside air without using fans or other mechanical systems. It can be via operable windows, louvers, or trickle vents when spaces are small and the architecture permits.
For residential buildings, which mostly rely on infiltration for meeting their ventilation needs, a common ventilation rate measure is the air change rate (or air changes per hour): the hourly ventilation rate divided by the volume of the space (I or ACH; units of 1/h). During the winter, ACH may range from 0.50 to 0.41 in a tightly air-sealed ...
A ridge vent is a type of vent installed at the peak of a sloped roof which allows warm, humid air to escape a building's attic. Ridge vents are most common on shingled residential buildings. Ridge vents are also used in industrial warehouses to help release the hot air and help circulate comfortable air inside the building .
Demand controlled ventilation (DCV) is a feedback control method to maintain indoor air quality that automatically adjusts the ventilation rate provided to a space in response to changes in conditions such as occupant number or indoor pollutant concentration. The most common indoor pollutants monitored in DCV systems are carbon dioxide and ...
The majority of guidance available for design of heat and smoke building vents installed in buildings is restricted to nonsprinklered, single-story buildings. [4] This is partly a historical consequence of the installation of heat and smoke vents following the August 1953 General Motors, Livonia, MI major fire in a nonsprinklered manufacturing facility which effectively stopped the production ...