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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 ...
Air is drawn from the workplace, around the worker and into the front of the hood, and is then exhausted out of the laboratory. Most laboratory hoods are described as constant air volume (CAV) hoods because they draw air constantly at all times. Rising energy costs have made these hoods exceptionally expensive to operate.
In most designs, conditioned (i.e. heated or cooled) air is drawn from the lab space into the fume hood and then dispersed via ducts into the outside atmosphere. [5] To reduce lab ventilation energy costs, variable air volume (VAV) systems are employed, which reduce the volume of the air exhausted as the fume hood sash is closed.
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.
Schematic of a network of rooms where air (shown in blue) flows in one direction from the corridor into the negative pressure room (green). Exhaust air is safely removed from the area through a ventilation system. Negative pressure is generated and maintained in a room by a ventilation system that continually attempts to move air out of the ...
HVAC (heating, ventilation, and air conditioning) is a major sub discipline of mechanical engineering. The goal of HVAC design is to balance indoor environmental comfort with other factors such as installation cost, ease of maintenance, and energy efficiency. The discipline of HVAC includes a large number of specialized terms and acronyms, many ...
A laminar flow cabinet blows unfiltered exhaust air towards the worker and is not safe for work with pathogenic agents, [2]: 13 [3] while a fume hood maintains negative pressure with constant exhaust to protect the user, but does not protect the work materials from contamination by the surrounding environment.
Local exhaust ventilation (LEV) is the application of an exhaust system at or near the source of contamination. If properly designed, it will be much more efficient at removing contaminants than dilution ventilation, requiring lower exhaust volumes, less make-up air, and, in many cases, lower costs.