Laboratory Fume Hoods with Active Auxiliary Air Supply Different Active Principles Make the Difference

Juergen Liebsch, Forschung und Entwicklung

A literature research on the history of development of laboratory fume hoods shows that exactly 50 years ago in the United States a patent was filed by JOSEPH BAYERN (1964) under the title FUME HOOD WITH AUXILIARY AIR SUPPLY. The patent should protect BAYERN's idea of blowing air actively into the inner space of the fume hood, instead of exclusively through the sash or bypass openings.

This early documented issue was followed by numerous approaches and attempts to the subject active auxiliary air supply until today. Not all of them were suitable for a successful transfer into practice.

The motivation of blowing auxiliary air directly into the fume hoods inner space can be quite different: One example is the reduction of the requirements to the laboratory air condition. The auxiliary air supply which goes directly into the fume hood, does not have to fulfill the requirements of the room air climate (temperature, humidity). This effect may lower energy cost and reduce the risk of air drafts due to the influence to the air exchange rate in the laboratory room.

Another approach is trying to influence the direction or the whole pattern at all of the airflow through the inner space of the fume hood. This may lead to a better containment behavior or faster dilution of dangerous substances.

Or following another physical principle: wall jets should reduce turbulences and backflows at the leading edges of the worktop and sidewalls of the fume hood.

As a further example the usage of blowing air actively into the fume hood for creating an air curtain which should improve the containment abilities of the fume hood with the front sash at the open position.

The presentation will give an overview about the developmental history of the different active auxiliary air supply systems in laboratory fume hoods, their different (theoretical) physical active principles and last but not least an quantitative comparison of the today available state-of-the-art systems.

Learning Objectives

  • Explanation of the motivation of blowing auxiliary air directly into the fume hoods
  • Giving the background of the developmental history from the first idea to the state of the art
  • Explanation of the different physical impact principles of the different methods

Biographies:

Juergen Liebsch, a former member of the executive board of Waldner was mainly responsible for all the company's R & D activities. Meanwhile he operates his own firm—Research and Development in the laboratory field focused on the fluid dynamics of fume hoods. More than 20 patents are issued in his name. He is a member of different working groups at DIN—the German committee for standardizing laboratory furniture and fume hoods, and of CEN—the European committee for standardizing laboratory fume hoods.

 

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