I purchased this fan to create negative pressure in a room that I am grinding the concrete floor. The 12 inch fan is adequate and makes a noticeable difference, compared to no fan. Be sure to have make up air available to facilitate airflow. I opened the attic hatch in this room. The 30 ft tube is great. Remember that the flex tube is made for exhausting the fan unit. Not for suction or intake. I saw reviews where people were trying to suck air through the tube. The fan unit was placed in the room I was working in , the tube was routed outside the house through the garage. The grass outside at the end of the tube was coated in concrete dust. I can't see the smaller versions working as well as this model does. I would buy again.
Paul 
Joe 
