Couple of venting questions:
What type of vent are you using? Is it one for painting/fumes? I ask because most bathroom/kitchen vents contain brush motors. This can be extremely dangerous as the brushes cause friction (small sparks) which could ignite certain paint fumes. You really want to use a brushless motor fan.
Second, what CFM rating is the fan? A weak "pull" will not fully vent to the end of your run
Speaking of your run, how far is it? for your cubic footage, you need to have minimum 60 CFM vent motor. This will pull the fumes up to 50 ft. Also know that any 90 degree angles add 5 feet to your total run length.
Lastly, what type of vent hose are you using? Just regular plastic/foil vent is still a bit porous, and will let fumes out. You want rigid venting to really contain anything. Also, your venting should attach to the fan INSIDE your box. Obviously, you want to make sure your box is also as air tight as possible. Duct tape or aluminum tape helps seal any connections too.
This may seem like overkill for a temporary project, but hey, you asked