Types of Exhaust Systems and Fume Hoods

Auxiliary Air

• Auxiliary air exhaust systems work by bringing in supplemental air for the hood exhaust so that the percentage of modified air removed from the room is limited. However, this method uses technology that is outdated and does not work well in climate-changing areas, because the hot or cold air being brought in can make for uncomfortable working conditions.

Constant Air Volume

• At the front of most fume hoods is a movable sash that is part of a counterbalance mechanism. In a constant air volume (CAV) exhaust system, air is pulled in through a bypass that widens as the sash opening gets smaller. This allows the air flow going through the hood to remain constant, regardless of the fan speed or where the sash is positioned.

Variable Air Volume

• In a variable air volume (VAV) exhaust system, the hood works in conjunction with the positioning of the sash to let the heating, ventilating and air conditioning (HVAC) system know the degree to which the sash is open. This information then lets the system know whether it should increase or decrease the volume of air to be exhausted.

Acid Digestion Hood

• When dealing with high concentrations of acids, special corrosion-resistant fume hoods are required. Acid digestion hoods are made out of polypropylene and polycarbonate, and often have ducts that are coated in Teflon. This makes them much more resistant to the corrosive effects of hazardous materials like hydrofluoric acid.

Low Flow / High Performance Hood

• Because traditional fume hoods can use almost three times as much energy as the average American home, fume hood manufacturers have come up with more energy efficient fume hoods that are designed to reduce HVAC operating costs. Some of the improvements made for low flow / high performance fume hoods include a more aerodynamic design for the sash, and a flush foil entry that provides maximum airflow to the work surface level and eliminates backflow.

Radioisotope Hood

• Radioisotope fume hoods are made from reinforced stainless steel that can handle the weight of the lead bricks used to study radioactive materials.

Scrubber Hood

• By absorbing fumes through a chamber filled with water-soaked plastic pieces and a neutralizing agent, scrubber hoods are able to clean toxic fumes before they are dispersed in a conventional manner.

Waterwash Hoods

• Waterwash fume hoods function just like a basic fume hood, except they have a special built-in cleaning system that washes out the interior of the unit and prevents the accumulation of dangerous chemical residue.