The main functions of laboratory fume hood.

The most importent functions for laboratory fume hood is discharging the waste air. In chemical laboratory, there will be many different kinds of substance including harmful gas, odor, moisture, flammable, explosive and corrosive substance during chemical operations. To protect the operators and prevent the pollutant during tests from expanding in laboratories. Fume hoods have to be used nearby the pollutant source.
The most importent purpose is to exhaust the harmful gas during experiment and protect the health of operators. It means that it’s necessary to have extreme safety and operability. So the following functions are required for lab fume hoods:

Laboratory Fume Hood Exhausting Function

It should be equipped with the functions that the harmful gas emerging in fume hoods can be thinned and discharged into outside of room by means of absorbing gas from working chamber. It’s best way to prevent harmful chemicals from hurting laboratory staffs. So sometime we call laboratory fume cupboard as safety fume hood.

Function Without Reversing for Lab Fume Hood

It should be with functions to prevent harmful air from flowing in reverse into room from inside of fume hoods. To ensure this function, it’s the best way to connect one fume hood with a ventilation fan with a single exhaust pipe. In case it’s not workable to use a single duct, parallel connection is only suitable for pipes in same room and in same floor. It’s better to install the ventilation fan at the end of pipe(or floor ceiling).

Fume Hood Supplement Function

There should be corridor for fume hood to absorb air from outside or replacement device when the waste air is discharged. It’s for exhausting waste air sucessfully. We call that corridor as airfoil, which can absorbing air from laboratory into working chamber of lab fume cupboard. It’s necessary condition to ensure normal exhaust working of fume hood with blower.

Function of Controlling Face Velocity

To prevent harmful gas from escaping inside of fume hood, it needs somewhat face velocity. The elements which decide the face velocity of fume hood when inletting air is the relation between heat produced for test items and times of changing air. Among them it’s the most important for test items and property of harmful substance. It’s stipulated in general that the innoxious pollutant is 0.25~0.38 m/s. The harmful pollutant with poison and danger is 0.4~0.5m/s. It’s 0.5~0.6m/s for pollutant with strong poison or with small amount of radioactivity. It’s 0.5m/s for gaseous material which it’s 1m/s for shot-like particle. To ensure such face velocity, the fan needs to have necessary static pressure. Also we need to pay attention to noise problem when we confirm wind speed. The limited value is 70dBA for background noise grade in laboratory. Increasing cross section area of pipe will reduce face velocity and lower noise. The power of pipe and exhaust fan needs to selected carefully considering of pipe cost and construction problem.

Lab Fume Hood Function of Heat and Acid Resistance

Sometimes it needs to place electricity stove in fume hood and there’s extreme strong corrosive harmful gas emerging during some tests. As a result, worktop of fume hood, baffle, water and gas fitting have to be equipped with with temperature and chemical resistance performance.

In general, it’s helpful to know above mentioned necessary functions. Then you know how many factors are critical for a qualified laboratory fume cupboard. When you choose laboratory fume hoods, you could get right model because you can check if existing fume hoods can meet those basic functions.