This instructable focuses on fitting a filter to a ventilator fan. To create a negative pressure in the work area you will need to put up a cloth or plastic sheet to block the doorway to the room, and will need to keep the windows closed. I use a strip door like P/N 8447A11 from McMaster.com (it's a little pricy, but I've used it on enough rooms that it has more than paid for itself). I've also made is a habit of using a sticky mat just outside the room (McMaster.com P/N: 6896T61 or similar) to help keep me from tracking out dust.
Step 1: Tools & Materials
• 8” 1,225 CFM Exhaust Fan, with 25' hose & connector
• Standard Pleated Panel Air Filters, 1" Thick, 12" X 12" (McMaster.com P/N: 2209K89 or similar)
• 8” round to 10” square duct adapter (You can get these at Lowes or Home Depot)
• ~16” X 8” 24Ga galvanized steel sheet metal scrap
￼￼￼￼• (20) 1/2” (13mm) pan head sheet metal screws
• (4) 2” drywall screws
• 4/4” X 14” X 6” softwood scrap
• (2) 10-32 X 2” pan head screws.
• (~2) 1/8" pop rivets.
• Caulking, like silicone, if needed.
• Saw (table saw works best, but you can do this with a hand saw or circular saw if you're careful).
• 1/8 drill bit, with countersinking shank or a 3/8 drill bit too.
• No. 2 Philips Bit for you drill or a N0. 2 Philips Screw Driver
• Marking punch
• Tape Measure
• Adjustable square
• Pop Rivet Gun
• 18" or longer quick clamps
• 3/4" hole saw (optional)
• Chisel or Utility Knife
• Screw Cutter or Hacksaw and File
Step 2: Modifying the 8” Round to 10” Square Adapter
Step 3: Disassembly of the Blower
Step 4: Installing the Round-Square Adapter
• Drill a hole at the 8” round lap joint and install a pop-rivet to lock the shape of the round.
• Install the intake screen just above the 8” round bead, and tighten the clips (this part can be a little bit of a pain, but be patient).
Step 5: Making the Filter Frame, Step 1
• Cut four pieces of wood for the frame, 1” X 3/4”; 2 that are 2” longer than two opposing edges of the square opening, and 2 that match the remaining edges of the opening.
Step 6: Making the Filter Frame, Step 2
Step 7: Making the Filter Frame, Step 3
Step 8: Attaching the Frame to the 10" Square
• Pre-assemble two corners of the frame.
• Clamp the frame to keep it in shape during handling (you don’t want to use the screws, as repeated tightening into end grain will strip them out quickly).
• Slip the frame in place on the 10” opening.
• Begin screwing the frame together, adjusting as needed to get a nice flat front face and square outer edge.
Make sure there aren’t any significant gaps. If there are, seal them with some sort of caulking. You should end up with the frame slightly larger than the filter.
Step 9: Fabricating the Filter Retainment
• Clamp the sheet metal down, overhanging a stout bench top you don’t mind hammering on. Use an adjustable square to get the overhang uniform.
• Hammer the bend flat along the long edge. Repeat to get a rolled over edge (so it isn't s sharp edge).
• Fabricate a corner as shown.
• Pre-drill and pop-rivet the corners.
• If the back of the rivet is longer than 3/16” (~4mm), snip off at that height with diagonal cutters.
• Hammer the rivets flat enough to not interfere with the filter when installed.
Step 10: Attaching the Filter Retainment
• Make sure the gap between the filter and frame is closed all the way around. Any visible gap will allow dust to simply be pumped out of the room and into the rest of the house in great volumes.
Step 11: Adjusting the Blower Feet Height
• Sawing out some feet extensions, 3/4” thick.
• Clean up the burs on the extensions.
• Remove the inlet end feet.
• Replace the existing rubber feet mounting screws with (2) 10-32 X 2”. Using a screw cutter to shorten the mounting screws so ~1/8” to 1/4” protrudes from top of the nuts when everything is reinstalled. All the rest of the hardware is reused.
Step 12: Final Touches
When transporting the ventilator, I compress the duct fully, reach in and grab the cord, pull it out the end of the duct and tie it to the blower handle. Works great.