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Fume hoods were introduced about 100 years ago to safeguard personnel working with hazardous materials. While many changes and improvements have been made, the basic concept and design of fume hoods remains the same. Air is drawn from the workplace, around the worker and into the front of the hood, and is then exhausted out of the laboratory.
Air flow in fume hood demonstrated by dry ice fog. A fume hood is typically a large piece of equipment enclosing six sides of a work area (including a movable sash window or door), the bottom of which is most commonly located at a standing work height (at least 28 to 34 inches (71 to 86 cm) above the floor).
A standard measurement, hood static pressure, provides information on airflow changes that affect hood performance. For hoods designed to prevent exposures to hazardous airborne contaminants, the American Conference of Governmental Industrial Hygienists recommends the installation of a fixed hood static pressure gauge. [8]
Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour.
Emissions or release parameters such as source location and height, type of source (i.e., fire, pool or vent stack) and exit velocity, exit temperature and mass flow rate or release rate. Terrain elevations at the source location and at the receptor location(s), such as nearby homes, schools, businesses and hospitals.
The infiltration rate is the volumetric flow rate of outside air into a building, typically in cubic feet per minute (CFM) or liters per second (LPS). The air exchange rate, (I), is the number of interior volume air changes that occur per hour, and has units of 1/h. The air exchange rate is also known as air changes per hour (ACH).
The draft (draught in British English) flow rate induced by the stack effect can be calculated with the equation presented below. [12] [13] The equation applies only to buildings where air is both inside and outside the buildings. For buildings with one or two floors, h is the height of the building and A is the flow area
Standard cubic centimeters per minute (SCCM) is a unit used to quantify the flow rate of a fluid. 1 SCCM is identical to 1 cm³ STP /min. Another expression of it would be Nml/min. Another expression of it would be Nml/min.
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