I'm setting up a small packaging operation for edible products for pets. There are certain government standards we have to hit to be able to do this.

The actual packaging takes place in a 420 sq ft room with 12 ft ceilings. It's all well sealed with a single door for entry and exit, that is itself pretty well sealed when closed.

In order to pass inspection we need to be able to demonstrate that the room is pressurized. There isn't a specific differential we need to maintain, we just need to be able to pass a smoke test at the door. The air needs to be filtered as well. It doesn't even have to be HEPA, just filtered. Pretty much I just need to be able to blow filtered air through the wall from the main area into this packaging room and get it nicely pressurized.

I spoke with one engineer who said "You don't need me for that, just get whatever you want and install it". He was pretty curt. I've been looking around and all I can find are inline duct fans for grow-ops (that sound like jet engines) and little bathroom fans.

What's my best bet for solving this problem? I know there isn't much to worry about in terms of installation, I'm just trying to avoid buying and installing something only to discover it's completely inadequate.


  • find a squirrel cage fan like what is used in central heating – jsotola Aug 17 '19 at 0:38
  • Do you also need air conditioning? – Harper - Reinstate Monica Aug 17 '19 at 3:06
  • A fan for those kids bouncy castle? – Solar Mike Aug 17 '19 at 5:05

It depends if you're looking for a "proper" solution or any workable solution, and your tolerance to noise.

It looks like filtering is one of your requirements, so you'll probably want to use a squirrel cage type fan, which is capable of developing the requisite pressure to push air past a filter.

Common sources of these fans: -Air purifiers (also filters the air for you), 100-600CFM depending on what you get, often cheap on Craigslist or Facebook Marketplace. Might be too small. ~25-200W. Also try "air scrubbers", available with higher CFMs like furnace blowers.

-Furnace blowers or old furnaces (cut the furnace part off, leave it, or just build a box) and filter, 2000-6000CFM. ~300-1000W. Usually has a few speeds. Also try "air makeup unit". Not toooo loud.

-Bathroom fans. Broan LoSone (pretty big)(300cfm) ~250W, Costco has some real quiet ones ~100cfm last I checked ~50W.

-Air mover blowers for drying floors or whatnot (need to rig a filter onto this), pretty cheap at Home Depot ~100-300w.

-Range hood fans - get a "chimmney style" one which will likely be squirrel cage and replace the grease catch filters with a furnace filter. Often cheap on Craigslist etc. ~200-400W.

-Hack a filter into a portable air conditioner or salvage the fan(take the "condenser" fan)

-Search Craigslist for words like "fan" or "blower" and find something that looks like it takes at least a few hundred watts

Crappy options: -Box fans with furnace filters on them -Induced draft blowers, small squirrel cage blowers, pressure blowers etc etc are a little too small for the room I think

Expensive options: -Proper air handler with filter -in line duct fans (unusually expensive for some reason)

Before you commit to installing something, try an experiment first: Tape up and seal the fan with filter rigged on to one of the doors with plastic or something, and make sure the plastic bulges out significantly.

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How about a bathroom fan, installed in a different room, that vents into this room. The room can be VERY small, and can house filters.

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    Since they don’t specify the filter media a bathroom fan and section of filter media cut to size should work, I purchase filter media in rolls and cut to size for fans on my motor control centers all the time + – Ed Beal Aug 18 '19 at 2:52

Look harder?

One example: A blower intended for inflating greenhouse plastic (blown between two plastic film layers to inflate them) on the small, but probably quite adequate, end. From a regular greenhouse supplier, presumably. Those are good at making static pressure, (usually of squirrel-cage design, not an axial fan, which don't do as well moving air against pressure) designed to run continuously, and fairly low power draw and noise level.

Another example: On the "cheap but prone to fail" side, a home kitchen range hood fan. Preferably (both kinds are made) a squirrel cage design. Or the "expensive but prone to last" version would be a commercial range hood fan, but I'm thinking that would be overkill.

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