Fume Hood Classes - An important consideration is the equipment type and its use

Ordering information for fume hoods-

Once the class of hood is determined there are a few more criteria to be determined before selecting your fume hood. The hood with all the traits you need should be selected. This could be either a large walk-in type unit to the common Control Air type bench hood to a special purpose unit. This determination is based on your lab or classroom needs.

When looking through the different types of hoods if one particular model does not fully compliment what you are trying to achieve we have an engineering group that will develop a system that works for you. This is really what Labcase has set out to do, develop systems for customers on an individual basis weather it is one hood or 100.

Once you have figured out the type and the specific needs you wish to achieve you must now select an operating type. The selections include Bypass, Low Air Flow constant volume, Add Air, and Restricted Bypass.

CONSTANT VOLUME EXHAUST SYSTEMS:

BYPASS - This is the air that is allowed to flow through the fume hood with the sash lowered to keep face velocities within an acceptable level. As the sash is lowered the face velocities rise allowing less air to move through the hood. The bypass helps maintain a clean environment within the hood keeping fumes, smoke, and particles moving into the exhaust. An airfoil of some kind or louvered front panel is typically used to achieve this.

To conserve energy and maintain a constant volume system see the Low Flow style hood in the Fume Hood section. You can greatly reduce the amount of air being pulled from your lab and still maintain a safe working environment. This is our most efficient hood offered

ADD AIR FUME HOODS WITH CONSTANT VOLUME EXHAUST - After consulting with an HVAC expert there maybe a determination that your lab cannot sufficiently supply the fume hood with enough air. In this case an Add Air system is recommended. The air is typically brought in from the outside or another part of the building. This air is dumped in front of the hoods face from above so as the sash opens the added air is taken. This results in higher hood efficiencies and reduced costs to temper your laboratories air. There are some drawbacks to this exhaust system, fore instance controlling the air and its moisture content so as not to interfere with experiments. The Add Air hoods must be balanced once installed.

RESTRICTED BYPASS - Constant volume operation with restricted bypass can be achieved with the help of proper exhaust duct sizing and face opening reducing devices. Use of an airfoil such as with the Labcase Airflow hood or sashes like horizontal and combination can also help. These sash designs can help reduce exhaust volumes as much as 50%. The reduced exhaust volume helps the bypass air volume to be reduced and in doing so still achieve constant volume.

VARIABLE AIR VOLUME (VAV) EXHAUST SYSTEMS:

It is recommended that all VAV systems use restricted bypass fume hoods to maintain the safety and energy savings within the lab. The intent behind the VAV system is to vary the exhaust volume in response to sash position. So as the sash opens up in order to maintain the same face velocity the exhaust volume increases as the sash closes a minimum of air is exhausted. All exhausted air is pulled from the lab/room the system operates in. All sash configurations can be used with this system. This system has its benefits with reduced energy costs but on the down side it is more sophisticated to operate and maintain compared to constant volume.

CONSIDERATIONS FOR FUME HOOD INSTALLATION:

Here are a few things to consider before and after the fume hood is installed. If it is possible when designing a new lab or including a fume hood to an existing one avoid locating the hood next to doors, windows, vents, or main walk ways. The reasoning is to reduce the amount of uncontrolled air near the hood and reduce foot traffic in front of the hood wich also causes disturbances in the air. Once the fume hood has been installed take the time to look over all the connections from the exhaust duct, fixture connections, and wiring. If there are problems consult with contractor to fix the problems related to the install. Once the hood has been looked over it must then be balanced when it is tied into an exhaust system. Bring in a qualified HVAC expert to balance your hood especially if you will be operating more than one unit on your exhaust system. Verify that the hoods face velocity is where it should be while testing the hood. A smoke test is a good way to see how well the system is functioning the hood should remove the smoke quickly and proficiently. Once the items above have been completed you should have years of service from your new fume hood.