Can you post a few pix and a sketch of your setup... Include distances if you can.

A few pitfalls...

1. Fan output on these units is rated for the fan alone - no inlet/exhaust ducting and no filter bag... If you have a copy of the fan curve - you can see how it drops off at various inches of water column (back pressure). Typical commercial and industrial fans are rated at 1/2" Water column back pressure. Often HF fans are pretty horrible - they drop off really fast as the system gets any restriction - like say the ducting and bag and safety grating over the fan inlet and exit to prevent fingers... Yes - this stuff comes from the factory.... But they don't include it in the ratings...

2. Ducting. Flex duct is horrible for back pressure/friction losses. A 10 ft run of flex can cut your CFM in half... And that doesn't count the losses from the filter bag...

3. Are you trying to vent the whole space or pick up the fumes from your machine? These things work WAY better pulling the fumes directly off the machine as close to the point of generation as possible. It takes a huge amount of ventilation if you are trying to vent "The Room"....

4. Outside air source? Whatever blows out has to be replaced with something. This has already been mentioned - but it's critical to have a source for fresh air to come into the area. And it's critical that this source is far away from the discharge so it isn't sucked right back in.... For example - open a window on the opposite wall?