Where is fresh air supposed to come from

You need intake and output for proper ventilation

I hate saying this so causally but You need a better fan…. Not too long ago someone’s advice to me was you need to make more money.. I thought how fucking contrite of this asshole but after awhile I realized he was right and it was the best advice I have ever been given.. so you need a better set up all together. An in-line duct fan that moves no less than 50 cfm would probably do but 150 would be better

Widen the intake, and make sure the fan has enough CFM to draw that volume of air through it.

We have one floor vent in the room that is not sealed, so fresh air comes from there. The return vent is sealed to keep the smoke out of the house system.

I mean, it's a pretty decent utility fan. It moves enough air to inflate that garbage bag pretty well.

You need a much bigger fan and a much bigger intake. You're not getting good results because you're pushing a fan of unknown cfm with a 2" intake, expecting it to effectively clear a room efficiently.

How big is the room? How many cubic feet are you trying to clear, and what would be efficient enough? An 8'x10'x8' room is 640 cu ft. A 50cfm fan would take nearly 13 minutes to clear the room, where a 150cfm fan would do it in a little over 4 minutes.

You need lots of outside air to come in, and lots of room air to go out.

Consider that kitchen hoods are typically mounted within 30-36” above the cooking surface. They already have the advantage that hot air rises toward them, and run from hundreds of CFM to 1200 CFM or higher. A 6” duct is recommended for a 600 CFM fan. At 1200 CFM and above, 10” is minimum. And of course you need sufficient makeup air. Without that you’ve just created a negatively pressurized room full of still air.

You mentioned a duct supplying the room with makeup air. But again if you don’t have air entering the house you’re just negatively pressurizing the house without creating air flow.

And where does the floor vent get its air? Unless the answer is “outside”, you probably aren’t bringing enough replacement air into the home to allow for much air to leave.

What's your budget for improvements? I'm thinking you could replace this whole set up for about $100 or less. Get a bathroom box fan 50-100 cfm and some more flexible ducting, run the ducting and fan close to the work surface/farther end of the room from the window, and then create another hole in your window setup to allow air in (same size ad your output hole)

I get the impression from your comment though that you're maybe looking to spend 0$? I think it's worth the small investment to save your health.

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Well, I can't really allow air back in through the window as I do work in winter as well.

You can try without doing an intake port, as you said you have a vent open from what I'm assuming is the heating system. Either way I think a bathroom box fan is an easy solution here, you can tinker with the rest.

As others said the big thing is getting a larger volume of air moving. A quick Google shows an electric air pump moves about 20 CFM where a cheap bathroom fan does around 50 or more. So triple, ish.

Someone else in the comments already did the math for how long it takes to clear a room with different CFMs but I think it's pretty clear an electric air pump is just not gonna cut it.

This assumes air is able to flow in from outside of the house. Otherwise some air will be drawn out at first, and then the fan will just be maintaining a slight vacuum in the home.

Those will happily hook up to a dust collection system and can also hook up to a shop vac. Some fans simply haven’t got the power to push against a pressure differential such as a breeze blowing the wrong way. Shop vac is noisy but will definitely do the job. I know you don’t want to leave a shop vac outside (nature abhors a vacuum) but the basic theme here is you need to really move a decent amount of air with a purpose built suction system of some kind. A more powerful fan would be a good place to start.

I built an exhaust table to be able to airbrush with toxic paints. Mounted two 400 cfm fans under the table and vented through the wall. I went with Tjernlund fans after I saw a demo on you tube. https://www.amazon.com/gp/product/B005XNNYMU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 The fans are currently $90 each on Amazon. They are 6” inline duct fans, vented independently out the wall. More bang for your buck w an 8” 460 cfm at $85 or a 10” 870 cfm for $156. Like people said you’ll need a fresh air intake too.

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Gee thanks.