Fume Hood - Ducted Fume Hoods

Ducted Fume Hoods

Most fume hoods for industrial purposes are ducted. A large variety of ducted fume hoods exist. 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 atmosphere.

The fume hood is only one piece of the lab ventilation system. As the recirculation of lab air to the rest of the facility is not permitted, air handling units serving the non-laboratory areas are kept segregated from the laboratory units. As a means of improving indoor air quality, some laboratories also utilize single-pass air handling systems, where air that is heated or cooled is used only once prior to discharge. Many laboratories continue to utilize return air systems to the laboratory areas to minimize energy and running costs, while still providing adequate ventilation rates for acceptable working conditions. The fume hoods serve to evacuate hazardous levels of contaminant.

To reduce lab ventilation costs, variable air volume (VAV) systems are employed, which reduce the volume of the air exhausted as the fume hood sash is closed. This product is often enhanced by an automatic sash closing device, which will close the fume hood sash when the user leaves the fume hood face. The result is that the hoods are operating at the minimum exhaust volume whenever no one is actually working in front of them.

Since the typical fume hood in US climates uses 3.5-times as much energy as a home, the reduction or minimization of exhaust volume is particularly beneficial in reducing facility energy costs as well as minimizing the impact on the facility infrastructure and the environment. Particular attention must be paid to the discharge location, so as not to risk public safety, or to pull the exhaust air back into the building supply air system.