Introduction to the basic principles of fume hoods

Cabinet exhaust hood, commonly known as fume hood, is similar
to a closed hood.

Small parts paint cabinets, chemical test room fume hoods are typical structures
of cabinet exhaust hoods.

Large chamber fume hood, one side open, the operator works in the cabinet, mainly used for large parts of painting, powder bagging and so on
.

The working port of the fume hood has a great influence on the airflow distribution in the cabinet, and the airflow distribution directly affects the working effect
of the cabinet-type exhaust hood.

Local exhaust hoods are an important part
of the local exhaust system.

Its efficiency has a very important impact on
the technical and economic performance of the entire exhaust system.

Well-designed local exhaust hoods can obtain better control effects with a small air volume and ensure that the concentration of harmful substances in the working area meets the provisions of
national health standards.

The exhaust hood is divided according to the degree of sealing, and there are closed exhaust hoods, semi-closed exhaust hoods and open exhaust hoods
.

Semi-closed exhaust hood refers to an exhaust hood that is often unable to partially close the contaminant generating equipment or due to operational needs, and must be opened with a larger working hole
.

Fume hoods are one type of this type of semi-closed exhaust hood
.

Fume hoods generally come in three forms, the difference being that the exhaust outlets are positioned differently and are suitable for contaminants
of different densities.

Pollutant density hours with upper exhaust air; Use the lower exhaust air when the density is large; When the density is uncertain, the upper and lower exhaust air can be selected at the same time, and the upper exhaust outlet can be adjusted
.

The door of the fume hood can be adjusted up and down, and under the condition of operation permit, the smaller the opening degree of the cabinet door, the better, so that it has a better effect
under the same exhaust air volume.

The ability of the fume hood to control pollutants mainly depends on the wind speed at the opening, and the wind speed at the opening is generally recommended to be 0.
3 to 1.
5 m/s
.