1. All-steel fume hoods are divided into three categories according to the exhaust: upper exhaust type, lower exhaust type and upper and lower simultaneous exhaust type.

        1. It is required to use an upper exhaust fume hood for thermal process treatment.

       2. In order to ensure uniform wind speed in the work area, the fume hood used for the cold process should adopt the bottom exhaust type.

        3. For processes where the heat generation is unstable, air outlets can be provided on the upper and lower sides to adjust the ratio of the upper and lower exhaust volumes according to the changes in the heat generation in the cabinet to obtain a uniform wind speed.

        2.All steel fume hoodClassified according to the air inlet mode: variable air volume type and full exhaust type.

        1. Full exhaust type equipment is a widely used type. The indoor air is circulated in the cabinet and then discharged to the outside, which is called full exhaust type.

       2. Variable air volume equipment includes ordinary fixed air volume system and standard type. The standard type has low cost and variable air volume cost is high. It is suitable for occasions requiring high precision.