indoor dust/fume hood (which fan to use?)

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i'm moving my headlight operations into the basement for winter, and will need to do some dremeling/drilling of plastic, rattle can spray painting, epoxy mixing etc. I would like a way to exhaust fumes and dust via a fume hood. Luckily there is a basement window right next to my workspace, so I plan to build a dummy window with a flange for ducting and exhaust straight outside.my first question is, what kind of fan would you guys use for this? I would like something relatively quiet, 110v, and adjustable. Adjustability can be achieved with a fan speed controller, so that part is figured out.my biggest hurdle is determining what CFM I really need. My box will have a volume of 20 cf (2.5 x 2.5 x 3 rounded up), and an opening of 6 sqft. What type of exchange rate is needed to keep stuff from exiting the box?here's to hoping that there are some guys with hvac experience who can help me tackle thisi dont want to buy a 250 cfm squirrel cage fan and have it try to suck my brain out my ears
Reply:so after doing more research it appears a face velocity of 60-100 linear fpm is OSHA standard for chemistry fume hoods... but I won't be working with any fumes heavier than air, which that number takes into consideration. it's dust, aerosol paint cans, and mixing small batches of epoxyIf I aim for a minimum of 50 lfpm at the face, that should be fine methinks.if I reduce my opening to 1.5' x 3' (4.5 sqft), that means that 4.5*50 = 225 cfm to achieve that face velocitydoes 225 cfm sound reasonable or way too high?
Reply:I just installed a exhaust system in a garage to clear exhaust fumes from cars that are running. I also just redid my Kitchen and had a blower from a Jenn-Air cooktop with a downdraft left over. It had a 6" intake and a 5" exhaust and it ran so quite, you had to be sure to turn it off when done. It worked out great. I have since acquired another one from a Jenn-Air stove with a downdraft for furture projects. Now the only thing I would be concerned with in your case would be the rattle can fumes. As I'm sure this blower does not have an explosive-proof motor. It may or may not be a problem. Just letting you know what worked for me.
Reply:Thanks john! i appreciate the post. definitely some good things to think about.Best wishes,Luke
Reply:I will make this contribution, remote mount the fan as far out of the room for noise reasons. The quieter the system the more you will use it. Remember the air you are taking out has to come from  some were.
Reply:also remember that not only does your fan motor need to be explosion proof but the fan enclosure (so as to not build up a static charge and grenade your fumes) and that fumes like paint can blow up your house from the furnace or hot water heater pilot lights. just something to keep in mind....Miller thunderbolt 250Decastar 135ERecovering tool-o-holic ESAB OAI have been interested or involved in Electrical, Fire Alarm, Auto, Marine, Welding, Electronics ETC to name a just a few. So YES you can own too many tools.
Reply:Also... the rattle cans will more than likely contain propane in the propellant... which is heavier than air... but it sounds like you will be doing very small areas so the likelihood of you building up to explosive concentrations should be small... not sure of the calculations on that one though...The best solution could be a belt/shaft driven squirrel cage blower ... locate the motor outside the volatile fume area and all is good.. then you can also pulley down the fan speed as needed... also setting up the fan speed via pulleys means you can use a fixed speed motor, and there are many options for brushless (sparkless) motors out there.Last edited by pandinus; 11-28-2010 at 10:13 PM.Never argue with an idiot. They drag you down to their level, then beat you with years of experience.
Reply:If your doing small painting with the rattle cans i would spray it outside and then bring it in right away to dry since it will be cold out. I do this sometimes during the cold so i don't have to deal with the fumes or open my garage door and loose all my heat. As long as your quick and bring it in to dry right away it will dry just fine.Ya gotta spend money to make money!
Reply:Originally Posted by welderShaneIf your doing small painting with the rattle cans i would spray it outside and then bring it in right away to dry since it will be cold out. I do this sometimes during the cold so i don't have to deal with the fumes or open my garage door and loose all my heat. As long as your quick and bring it in to dry right away it will dry just fine.
Reply:If you re-purpose some sort of squirrel cage or hvac duct fan or blower, look for one that has three speeds. I have an old squirrel cage out of a gas pack or central hvac system. It has three speeds ranging from "gentle breeze mode" all the way to "vertical takeoff mode." This allows me to changer fan velocity to to roughly correspond to the nastiness of the things that need to be vented.It wasn't skill that lead me to understand the value this feature. It was pure dumb luck. :-)
Reply:i dont' want to make anyone legally responsible, so let's just say I waive my right to sue you if you give me advice that results in my injury are brushless motors technically sparkless? or is there more to it than just thatand yes, I dont anticipate the air mixture to be explosive, but anticipate and know are two different things