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The Digital Fume Hoods VAV kit

An explanation into laboratory fume hood design and operation

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Definition

According to the European standard EN 14175-1:2003, a laboratory fume hood is a “protective device to be ventilated by an induced flow of air through an adjustable working opening, with an enclosure designed to limit the spread of airborne contaminants to operators and other personnel outside the device, offering a degree of mechanical protection, and providing for the controlled release of airborne contaminants.”

 

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Key elements of a fume hood

A fume hood must pull an adequate volume of air through the open sash.

The speed of this air, as it passes through the sash, is called face velocity

This is just one of the parameters considered by regulations to establish if a fume hood is meeting the safety criteria.

Baffles are located at the back of a fume hood. Their purpose is to direct the exhaust air in a uniform manner. At the top of the hood, a damper (or vent) adjusts the quantity of air to be exhausted.

It has been mathematically verified that the correct operation of the fume hood is related to the creation of a “stable vortex” in the hood’s upper chamber.

Critical operating factors for laboratory safety

A fume hood operation is affected by any environmental disturbance:

  • Personnel walking by
  • Room pressure changes
  • Sash movements
  • Fume hood loading
  • Air filters jamming
  • Other operating fume hoods located in the same room
  • Incorrect equipment position

A fume hood control system must maintain a stable vortex, whatever the position of the sash, operators, and equipment, while minimizing air extraction.

Measuring fume hood efficiency

How do you measure fume hood efficiency in preventing inhalation of chemicals by laboratory operators? Is it true that a fume hood face velocity is a measure of its efficiency?

 

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