A vibrating screen is made in two versions, single blower and double blower. The standard model is the single blower type. The two look much the same from the front, and the difference sits at the back of the machine.
The double blower version carries an additional blower on the back side of the screen. Its job is rear suction, and with two fans running the machine pulls back the light impurities that would otherwise be blown out. Those impurities are collected rather than scattered, which makes the unit more environmentally friendly in use.
On the standard model there is no rear suction, only the blowing fan. Light impurities are blown out of the material but cannot be collected. They end up on the ground behind the machine, where they have to be swept up later.
The choice therefore comes down to where the screen works and how strict the site is about dust. Where the screen runs indoors or in a workshop, the double blower keeps the floor and the air cleaner. Where the machine works outdoors and dust is not an issue, the standard single blower covers the job.
