Jonathan Beard
27 January 2000

Image of a fumehood at Lawrence Berkeley National Laboratory

A typical American fume hood, Bell said, is about 6 feet wide, 2 to 3 feet high, and contains a fan that sucks air in, so it can be vented out the top, at 100 feet per minute. The LBNL design cuts down on this high-speed air flow by using a push-pull approach. "Small fans are located at the top and bottom of the hood's face, pushing some air into the hood, and some into the user's face," said Bell. "This creates an 'air divider' zone, separating the user from the interior. Since there is a barrier preventing inside air from escaping into the room, the exhaust fan can be run at a much lower velocity." Bell said the hoods, which will be tested in a facility in Bozeman, Montana, "...will reduce the flow to 30% of a conventional hood. And the building's environmental conditioning system can be downsized, saving construction and operating costs."

Bell said that the LBNL team has applied for patents on the new design, "which involves a rearrangement of the interior of the hood, as well as the supply fans in the front sash." He said that the new design should offer improved safety, in part because the very high airflows of present designs can, if a user stands right in front of the hood, cause blow-back similar to what one observes in holding up one's hand to shield a candle from the wind.

"We hope to incorporate additional energy-saving features in future hoods," Bell said. "Electronic sensors that could sense that no one was using a hood could be combined with the low-flow features to reduce airflow, saving even more money. One of the reasons today's fume hoods are so wasteful is that they are run at full force all day long."