A fresh air intake from outside of the room (could be from the attic or through the wall to outside) will draw air into the machine so you are not sucking the HVAC out of the room (sealing your machine is a good step in this process as well). My old machine had a collar specifically for air intake, but my new machine does not. I built a plenum on my new machine.
Next is good quality ducting. I use 6" flexible ducting connected to metal take offs on the machine to prevent melting.
Your extraction impeller would ideally be outside of the room. I have mine build in to the exterior wall. You want the line within the room to always be under suction. Also having the fan outside greatly reduces the noise.
As for the impeller, if you can find this style of a used SPIN MASTER bounce house blower, it is a MONSTER and will work better than most anything you will find. However, even the cheaper impeller based extractors move a lot of air under decent static pressure.
If you go the route of fresh air intake and venting outside, I highly recommend having blast gates on the ducting. Otherwise, if you leave the machine lid closed in an air conditioned room on a hot humid day, you will build up condensation in the machine.
Question: How are you cutting acrylic with Diode Lasers (as shown in your profile)? Edit: Nevermind… the title of the post… (time to update your profile and machine #3)
One more item to note: My fume extraction is 100% automated. When a job starts, my controller signals to open both blast gates (as illustrated in a previous link above) and start the extractor on a delay relay.