How Does A Fume Hood Operate?
Fume hoods are designed to protect personnel from toxic or volatile chemical gases, vapors and fumes. In both ducted and ductless fume hoods, room air enters the hood through the sash either vertically or horizontally, depending on the design. The sash also acts as a barrier between the worker and the inside of the fume hood and provides limited protection.
As the airflow works through the middle of the fume hood, it pushes the harmful gases, vapors and fumes toward the exhaust area. This area is managed by slots and baffles, which act as exit doors for the fume hood before reaching either the connected ductwork (ducted fume hood) or the fume hood filters (ductless fume hood). In many fume hoods, the slots and baffles are adjusted to allow for even airflow. If the baffles are closed (or blocked), the exhaust path will also be blocked. But when used properly, baffles eliminate dead spots or reverse air flows which would result in a loss of containment. In ducted fume hoods, an exhaust fan pulls airborne contaminants through facility ductwork. Air is then filtered or treated before being exhausted into the outside environment.
How Does a Ductless Fume Hood Operate?
Ductless fume hoods use activated carbon filters inside the unit to capture vapors before recirculating the clean air directly into the laboratory. Ductless fume hoods offer the same protection as ducted models. Ductless fume hoods are equipped with numerous technological advances to enhance safety and function. Low airflow alarms ensure the proper containment of fumes inside the hood, filter saturation alarms help maintain near-to-zero chemical emissions in recirculated air, and backup safety filters protect against filter malfunction.
The biggest differences between ducted fume hoods and ductless fume hoods are that the latter are more convenient and less expensive to install, and are highly energy efficient. Facilities with multiple fume hoods see substantial energy consumption savings from the use of ductless fume hoods when compared to ducted fume hoods.
Air Science manufactures a complete series of high-efficiency ductless fume hoods designed to protect the user, the process and the environment from hazardous vapors and fumes.