Shop ventilation

[alexy]

I have a basement shop that takes up about 1/3 of my basement. Whenever I finish a project, I find that the sweet aroma of turpentine or linseed oil permeates the house. SWMBO agrees, substituting "awful smell" for "sweet aroma". I'd like to put in a small exhaust fan to the outside. The intent is not to exhaust the shop thoroughly -- I'm not spraying or using real dangerous chemicals -- but just to create enough pressure differential to make sure that all the leaks between my shop and living space result in air moving into, not out of, the shop.

My question is how to size the exhaust fan. My shop area is about

600ft^2x8ft ceilings, with no windows, one 30" door, and lots of holes around pipes, ductwork, etc. going into the rest of the house. I already have a 4" and a 6" duct running through the basement to the outside, from the drier and stove exhaust. I'm thinking maybe to Y into one of these before an inline fan. Might need some kind of flap valve to keep drier lint or cooking smells out of the shop.

Any ideas from this creative group? Source of fans?

[Bob S.]

Alexy,

First of all, it probably isn't a real good idea to Y into any existing vents that are venting gas fired appliances. Lot's of things like back-flow pressures allowing gas fumes back into the house, snuffing out pilot lights (if you have them), not to mention a few code violations too.

One of the most economical solutions I can think of that doesn't present dangers like above is a simple, through-the-wall, powered vent as found at the borg's for venting bathrooms/washrooms, utility areas. You didn't mention where you live but they have models that can be used for any climate and have appropriate sized motors, fans and louver opening mechanisms that are sized to fit the CFM requirements for your work space.

By exhausting the air, you also need to have incoming air to replace what's being forced outside. This air exchange may be costly if you are venting warm, heated air with cold outside air in the winter or vise-versa in the summer if you use AC.

If the vapors are simply "smelly" and non-toxic that you want to deodorize, then turn on a small floor fan, place an open container with a 50/50 mixture of "ODO-BAN" (Sam's Club) and water in front of it. That stuff smells okay and it deodorizes - not just masking odors like some can sprays do. Even a mixture of vanilla or citrus juices in water will usually do well to make it smell better. Then there are the electronic cleaner solutions, electrostatic air cleaners with carbon filters etc.

No matter which solution you try, plugging the holes to the upstairs areas is a must and as you'll discover, not a small task once you really start looking for all the places fumes can escape up through.

Good luck and I'm sure others will have some good ideas.

Bob S.

[Edwin Pawlowski]

Step one is to leave the existing vents alone. I can just imagine turpentine fumes getting into the dryer. No code would allow that, but hazards aside, your wife would go bonkers if the load of undies took on a linseed oil smell.

Do you want to duct outside trough a vent? I'd look at the wall mounted exhaust that is typical to a kitchen. The little ones for a bathroom don't do enough to warrant the installation time IMO.

Depending on where the windows are, a 10" box fan sitting in the window may pull enough from your shop area to keep the odors from infiltrating the house. Ed

[Morgans]

Go by a heating cooling shop. Ask if you can get the squirrel cage blower out of the next furnace they replace. Anything other than a centrifugal blower will not create the pressure differential you are looking for.

[Phil Crow]

oughtta do the trick.

Seriously, bigger is better. I would imagine you could put a rheostat on any fan to decrease air flow if it's _too_ much.

-Phil Crow

[RESPITE95]

I have a large fan in a window that opens and closes as the fan is turned on or off. I use a lathe in front of the fan. I also have a much smaller screened opening that can be closed located in a solid core door on the other side of the room. I keep the small opening open all spring, summer and fall, close it in the winter. The big window fan will pull out dust, fumes and your shirt if you are not careful. Works well for me. GCS

[admin]

Basis sizing fans for bathrooms, one needs a bit over 1CFM/sq.ft. Theoretically, this'll change the air about 8 times/hr, assuming 8' ceilings.

For your shop, it works out to about 650cfm.

The *BAD*NEWS* -- 650 CFM through a 6" duct requires an air velocity of nearly FORTY MILES PER HOUR.

reducing things to 5 air changes/hr, gives 400 CFM, and a velocity of about

24 mph in 6" pipe. still on the high side.

Go to 8" duct, and you're down to 13mph. this sounds more rational.

[Erik Ahrens]

I realized something in your description of the basement - It appears you have only one entrance/exit. Is there any way you can get a window in that's big enough to crawl through in an emergency? I really don't want to read about how nice a guy you were in the news.

Erik

[alexy]

Thanks for the concern, but the daylight side of the basement got to be family room and lawn mower, edger, etc. storage, while my office and the shop got the underground side. Guess if I didn't have access to the door, I would be busting out drywall into an adjacent room. Never really thought about that, until you brought it up.

[alexy]

Boy, you've got that right!

Sounds like what I need to look into. Thanks.

[alexy]

Okay. I hadn't thought about the humid air vent from the gas drier also being burner exhaust. The stove exhaust is just for cooking odors, not a vent of combustion gasses (unless something catches fire on the stove).

Thanks. I'll look into that.

Atlanta

Yeah. I will try to stop up as many leaks as possible, thus lowering the amount of air I have to move to keep smells from escaping, and also to minimize heat and a/c loss.

I'll have to look for this. thanks for the pointer.

I'd forgotten about that. The fire dept recommended vanilla when I had a smoke problem 25 years ago. Amazing how well it works for that, but never thought of it in this application.

[Larry Jaques]

On 27 Oct 2003 16:32:07 -0800, [e-mail] (Phil Crow) brought forth from the murky depths:

Hey, that even warms the air as it ventilates, doesn't it? Great for the coming winter, eh?

[Geoff M]

Ahh, at last a post I can answer. For 650 CFM, you will need ~12" duct to get an acceptable flow rate, matched to a good 300mm axial fan. You could go smaller if you use a good centrifugal fan, but 10" would probalby be close to the limit Geoff