# Shop ventilation



## KevinD (Aug 11, 2014)

This may be so simple I'm overlooking something, but what do you all do to clear the air in your shop?  My lathe/mill room is 11'X19' and when I get to cutting on either machine things can get pretty smoky in there.  Typically I'll set up a fan to blow air out of the shop and another to blow in fresh air.  But with this last winter being so cold that was a bit of a non-starter for getting stuff done.

I use the cutting oil with sulfur and I'm sure that doesn't help much.   I have bought a bathroom vent fan but haven't installed it as it seems the vent fan in the house isn't all that effective.  Just a weak negative pressure judging by the fog on the mirror after a shower.  And then I don't want to install a vent fan over each machine, to blow into the bigger shop.  What am I missing here?

I have hooked up a sump pump hose to my welding hood that runs outside air from a shaded pole blower over my face for welding projects.  That helps a lot.  Just can't figure an equivalent for the machines.

Kevin


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## racardon (Aug 16, 2014)

For general shop ventilation, you want to change the air every 3 to 5 minutes. Commercial restrooms run in the 3 minute range.
So assuming you and an 8 ft ceiling, 11 x 19 x 8 = 1672 cu.ft. For a 3 minute air change: 1672/3 = 557 cu.ft./min or cfm. For a 5 minute air change you are looking at 334 cfm.

A typical bathroom fan is rated at about 80 cfm. You can probably get 100 cfm ones at Lowes and Home Depot as well. So you are looking at 4 to 5 bathroom fans to do the job. Placing the fans directly over the machines will help control the fumes a lot. You can duct each of them to the outside separately or do a header. If you header them, you'll need about a 10 in diameter duct for the 3 minute air change and an 8 in diameter duct for the 5 minute air change.

You can buy bigger exhaust fans through places like McMaster-Carr.

The tougher problem is heating the air to replace all that exhaust. The equation for heating energy is Q = 1.08 x CFM x (Ti - To). I'm assuming Ohio is pretty near sea level, so the 1.08 factor does not need adjusted. Ti is your room temperature in degrees F (say 70). To is the outside temperature in degrees F (say 10). You'll have to look at the local weather to decide how cold of air you need to handle. Q will be in btu/hr.

So 1.08 x 557 x (70 - 10) = 36115 btu/hr which is about 10.5 kW. And 1.08 x 334 x (70 - 10) = 21669 btu/hr which is about 6.4 kW.

By the way, part of your bathroom problem with fogged mirrors is not the fan size, but how tight the room is. If you crack the door open just a 1/2 inch, you'll notice the fog will clear much faster. We used to always cut the bottoms of the bathroom doors to leave 1" clear between door and floor so the fan could get enough make up air.

Hope that helps,
Roger


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## JimDawson (Aug 16, 2014)

Roger, great write up, Thank you.


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## jpfabricator (Aug 16, 2014)

Could the bathroom vent fan be more efective if hooked to a flexable dryer duct tube. The end could be fastend to the backside of the saddle and evacuate at the source.

Jake Parker


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## JimDawson (Aug 16, 2014)

HF sells a axial vent fan and hoses.  I don't know about the quality, but I have looked at it and it looks OK on the shelf.  Item #97762  It should do a pretty good job of removing the smoke.


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## xalky (Aug 16, 2014)

I have one of these thru the roof and then I piped it down thru the ceiling. http://www.homedepot.com/p/Master-F...Shingle-Match-Weatherwood-PR3XDSMWW/100072633

I have it setup on a light switch. It clears the air in my 2 car garage in under a minute.


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## racardon (Aug 16, 2014)

Actually, catching the smoke at the source would be much better than the general exhaust approach I outlined. I'm not sure a bathroom exhaust fan would work well. One would have to jury rig a dryer hose connection with a nice transition to the fan. You can pick up small in-line fans. I found some by Suncourt (Centrax) and NuTone. links are below. I think 100 cfm would be plenty. I would guess they run less than $100 each.

The HF fan would work as well, but it is quite a bit over-sized (1590 cfm high speed, 1380 cfm low speed).

http://www.suncourt.com/Centrax.html

http://www.nutone.com/products/filter/remote-in-line-fans-bfd444a9-4e88-4e82-ba15-010b1c53a354

http://www.harborfreight.com/8-inch-portable-ventilator-97762.html

Roger


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## KevinD (Aug 18, 2014)

Those are some great ideas.  Thanks for the detailed explanation racardon, of course the desired effect is to minimize heat/cooling loss while optimizing the atmosphere.  Just opening the door and setting up a couple of fans can be like working outside, whether it's summer or winter.

I think the dryer vent hose of jpfabricator has some merit and with one-size-fits-all-duct tape could be easily hillbilly engineered to be placed near the offending process.  Does anyone have experience with carbon filtering?  I've seen those for general home application but can't imagine they would take care of the proliferation of fumes coming off a cutter.  And when Ohio went smoke free a few years back I likely missed the chance of getting one of those commercial smoke eaters for cheap.

on edit, a later revelation: I remember seeing the welding fume collector in a friends welding shop some years ago.  I suppose that would be the cats-ass as far as saving on the heating/cooling bill and portability.  Though the cabinet was fairly large, as I recall.  Maybe 4' tall and a yard deep.  Kind of klunky but I imagine a smaller more shop friendly box could be figured out... another addition to the roundtoit list.


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## racardon (Aug 19, 2014)

A welding fume extractor would be a good way to go. The commercial ones are probably pretty pricey, though. I did a search for "diy welding fume exhaust". The following link has a pretty good idea.

http://www.millerwelds.com/resource...p?30612-Homemade-Fume-Extractor-For-About-100

I'm thinking one bathroom exhaust fan mounted close to the saddle on your lathe might do the trick.

I think activated charcoal or carbon filters would take out most of the smoke from your metal cutting. I don't think a bathroom exhaust fan is going to handle the pressure drop through filters though.

Several years ago, I picked up a blower out of a house furnace. I got mine out of the metal pile at our local dump back when you could scavenge. Anyway, I've thought about building a 16" plywood cube to put it in with a place for filters on the inlet side. Then I could hook it up to some duct work and use it to exhaust my shop. If I used activated charcoal filters, maybe I could just recirculate the air. Someday, I will put together some sketches, but don't hold your breath.
Roger


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## JohnG (Aug 19, 2014)

In cold climates air to air heat exchangers are used to hold down the heat loss of indoor/outdoor circulation.  The simplest setup is a long tube inside a tube.  The heated exhaust air passes out through the inner tube made of conductive material like aluminum, and cold air is drawn in through the outer tube.  They're becoming common in houses in places like North Dakota or Manitoba.  I don't know how the oil in the exhaust air would affect one. 

Most of my air issues are with mist from spray painting.  Right now I just keep it to a minimum when it's cold, so one of these is lower on my own to do list.


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## KevinD (Aug 20, 2014)

While cruising craigslist for a cheap welding fume extractor (I saw 20 year old one for $1700) I had a flash idea of making my own with some materials I had on hand (there's a long line of those projects).  Then had the thought that I already have a suction fan in the shop in the form of the shop vac.  A couple years ago I found an idea on the web and I modified my shop vac to sit on a 5 gal bucket so the oil and chips fall into the bucket while the filter stays relatively clean above the bucket the intake hose goes into.  I have ordered activated charcoal filters from Amazon to fit in the top portion of the vacuum and will report back on how well it works, or not.  The vac is too loud for prolonged use but will effect a decent, ready made suction and filter to see if the charcoal filters clean the smokey, oily air...


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## Rbeckett (Aug 21, 2014)

I have seen several good quality inline fans while searching for hydroponic supplies.  Most of them are available in a number of diameters up to 12 inches I think and are designed for continuous use.  I can't remember the CFM's but they are used to keep circulating fresh air in room sized growing systems.  They also have the inline carbon filters to reduce airborne pathogens and smells so the should also work for cleaning the air up quite nicely.  So have a look at some different hydro sites and see if they don't have what you are looking for.

Bob


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## KevinD (Aug 21, 2014)

Thanks Bob, will check it out.  The carbon filters from amazon should be here early next week.


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## KevinD (Sep 2, 2014)

Just an update, the carbon filter pads came today.  I'm not sure I'll have the chance to test them out before next week.  

Why does USPS call it tracking when it's not?  Jeesh, their system is really inadequate compared to the competition.


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## chhedausa (Jan 7, 2015)

I am using a Squirrel cage Stove exhaust to vent.  I am not sure on the exact cfm but it is about 3 to 4 times more than a typical bathroom exhaust.  If I would have to guess it is pushing 300 cfm.  It can also be outfitted with a filter instead of venting outside.

The noise is actually less than a bathroom exhaust.


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## SE18 (Jan 11, 2015)

I'm building a propane foundry to do some blacksmithing. A friend of mine has been using his to make knives for years. His setup is in his garage. He opens the garage doors. When I read the instructions on the propane regulator, it specifically says not to operate in any condition with an overhead roof or ceiling even if doors are open etc. Says it must be outside; which is pretty frigid this time of year!

Any incites apprec


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## coolidge (Jan 11, 2015)

I did a bunch of MIG welding recently in my garage shop, I opened the garage doors and used a 'high velocity' fan I purchased at my local Wilco Farm store. I set it on a mobile work table about 30 inches high near the welding table and aimed it out the door. Its an all steel fan and they are not kidding about high velocity at its lowest speed its like an airplane propeller WHAAAAHH. There wasn't even a hint of smoke in the garage it really moves some air. Under $40.

http://www.drillspot.com/products/574668/lakewood_engineering_and_mfg_1134wp_wp_18_hi_velocity_fan


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## SE18 (Jan 11, 2015)

thanks; I get cold thinking about a fan this time of year; another month or so and I'll start the foundry.


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## Terrywerm (Jan 11, 2015)

I am in the process of setting up my basement shop which will be for machining tasks only. All welding, heat treating, and (hopefully) eventual foundry work gets done in the garage with the doors open. Just the same, some sort of ventilation will be required for the basement shop for those pesky projects that get a little smoky when cutting from time to time or when doing some soldering or silver soldering. I initially considered just using a bathroom fan ducted out the side of the house. I don't mind if it takes a couple of minutes to clear the air, but if it takes too long, it would be no good. I also thought about using a small squirrel cage blower with a 2" or 3" hose positioned near the smoke source, using it only when necessary. Any thoughts anyone?


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## mskobier (Jan 12, 2015)

KevinD,
      In my line of work, we work with engineered ventilation systems quite a lot. Here is a very simple solution that may work for your problem. Your friendly neighborhood shop vac. If you place the open suction end of the 2" hose within approximately 2" of where the smoke is being generated, that will put the smoke in the capture zone of the shop vacs suction, and the gross majority will be sucked into the hose. The majority of the smoke is particulate, and the normal vacuum filter will remove most of it from the air. I would use one of the pleated paper filters with the foam sleeve over that. It is not nearly as efficient as a HEPA filter, but it will do a very good job of capturing the majority of the smoke particles. A better system would be an inline HEPA filter to a separate suction (blower), but for limited use, the vacuum will work fine. Yes, I know the shop vac is not the best solution, but I would bet money that you already have one, and could fab up some sort of mounting for the hose suction. You can also make a flattened funnel looking device to attach to the vacs suction to enlarge the capture zone. In normal HEPA ventilated systems, we design for an approximate 100-125 LFM of flow across the work opening to ensure adequate capture of airborne particulate. 

There are a number of companies who specialize in the design of ventilation systems. Do a web search on HEPA ventilation, and you should be able to find enough information to fabricate your owns system that is quite effective. 

Mitch


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## SE18 (Jan 13, 2015)

Thanks, my shop vac is the huge type and uses a lot of electricity and generates a lot of noise. It's capable of sucking in a small cat or puppy and maybe a small child. I think for the little bit of work I do, rather than install a vent system, I'll move my work outside in the driveway. To facilitate this, I'll look into adding wheels onto things that generate pollution like a furnace. The ideal solution, which the wife wouldn't like, would be to embed rails in the garage and driveway and wheel stuff out on flanged wheels. Steel shops, i notice, tend to do that with their heavy loads.


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## GA Gyro (Feb 6, 2015)

If you shop around some, you can find bathroom exhaust fans that vent into 4" dryer vent tube... and are rated in the 100-150-200 CFM range. 

Seems to me if one put one of those above each machine... and used it as they needed... they would move enough smoke away.  

Since my shop is in the basement of my home... I am gonna have to figure out something to keep the smell out of the house.  
One of the things is to not use soluble oil...


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## I#IronIII (Feb 8, 2015)

My situation.  I do both woodworking and metal work in a new 1500 sg/ft , 8" walls, well insulated shop with wood stove.  Winters here can be darn chilly, below zero and summers can be over 90 for more days than I like.  I don't like dust on my projects or machines and I'm sure most of the occasional welding / wood stove smoke or knife dust isn't good to breath.  And being retired I basically live in my shop.  I found a book on dust collection at the local Woodcraft store (can't remember the name, somebody borrowed it) that studied the dif options for collecting
that dust and cleaning the air we breath.  Bottom line, a box fan with a furnace filter taped to it was darn near as effective as the  $$$$ air cleaners.  I picked up a in-line air plenum booster fan, 1/10 hp, 1200 rpm, 7" double squirrel fan unit used for 20$, built a 18 X 25 plywood box to mount it.  I used two 16 x 25 furnace filters, one was full size the other I cut in half.  This covers one side and both ends of the box, it exhausts out the 4th side. The effectiveness of the filters gets better as they get a little dirty.  It is hung from a truss in the center of the shop, and is powered thru a router speed control box.  It runs 7 x 24 and keeps the dust / smoke / fumes out.  I've used this for over 8 yrs in my last two shops and love it.  I change the filters about once a month.  I can adjust the speed based on what is needed.  And I'm not wasting the heat or cooling.  This unit takes care of the stuff we breath and I use a roll around canister type shop vac at each machine to collect the heavier stuff.  Might be just another option.
Jack


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## Baithog (Feb 8, 2015)

My friend made his living making boxes. Sounds simple until you find out that his boxes are home theaters, libraries, and such for multi-million dollar homes. He has the box fan/furnace filter in his little shop. It'll clear the air well enough to varnish. IIRC he started using it back when he was doing the wood in yacht cabins. It doesn't do much for the smell of burning cutting oil. I solved that problem recently by going to a mist system. It sure beats breathing what is surely carcinogous smoke. If the little bit of mist bothers one, then one of our sponsors sells a fog free one. No more blue chips. No more smoke. No more petroleum smells leaking into the house. Cutters seem to last longer, too.

Ventilation is still a good thing, but you don't need a gale force blow of arctic air of a screaming sucker for hobby/small machining... just my simple minded opinion.


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## KevinD (Feb 13, 2015)

Ok, it's been a while since I checked in, roundtoits and all that.  But I found a solution to my problem, it's a bit of overkill, but it works just fine.  I was at a blacksmithing conference last fall and a friend had a Torrit fume sucker in the tailgate section.  I tried to buy it off of him but because I'd done him some favors when his ornamental iron shop was going out of business, he wouldn't tell me the price and eventually gave the unit to me!  

One of the projects that kept me from getting back to the forum was insulating my shop roof.  I'd found a place that was re-roofing and bought 100 of the 3.5" foam boards off of them.  A retired friend was able to cut and hand up pieces to me on the scaffold, but because he's due for knee surgery he wasn't able to help me up on the scaffold.  It was looking grim for a timely completion when I got in touch with a young horseshoeing acquaintance that could use some extra work.  The two of us on the scaffold could do in one day what was taking me 4 days by myself.  What a relief.  Last winter I'd run my wood stove for 3-4 hours and the temperature would go from 15° to 18°.  Looking forward to the new thermal resistance  ;o)

I like the idea of a fogless mist system, I'll check that one out.  Thanks.


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## KevinD (Feb 13, 2015)

Ok, it's been a while since I checked in, roundtoits and all that.  But I found a solution to my problem, it's a bit of overkill, but it works just fine.  I was at a blacksmithing conference last fall and a friend had a Torrit fume sucker in the tailgate section.  I tried to buy it off of him but because I'd done him some favors when his ornamental iron shop was going out of business, he wouldn't tell me the price and eventually gave the unit to me!  

One of the projects that kept me from getting back to the forum was insulating my shop roof.  I'd found a place that was re-roofing and bought 100 of the 3.5" foam boards off of them.  A retired friend was able to cut and hand up pieces to me on the scaffold, but because he's due for knee surgery he wasn't able to help me up on the scaffold.  It was looking grim for a timely completion when I got in touch with a young horseshoeing acquaintance that could use some extra work.  The two of us on the scaffold could do in one day what was taking me 4 days by myself.  What a relief.  Last winter I'd run my wood stove for 3-4 hours and the temperature would go from 15° to 18°.  Looking forward to the new thermal resistance  ;o)

I like the idea of a fogless mist system, I'll check that one out.  Thanks.


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## roygpa (Feb 13, 2015)

When I built a couple of 3D printers, my wife complained about the ABS fumes. Since the printers use 12 volts DC I bought a boat bilge blower that also runs on 12 Volts. I hooked it to speed pot that I bought on ebay and it works great. I use dryer vent hose. Built a temporary exhaust vent to fit the window to vents though so that I don't lose too much heat from the room. 

Roy


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## w9jbc (Feb 13, 2015)

I guess I never gave it much thought myself. I spent way too many hrs around screw machines to get too concerned about it. where bar machines are there is bound to be smoke & noise!


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