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harry robinette

Small smithy ventilation

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My smithy is only 8' x 12'. Have 3 burner gas and a 18" rivet forge the rivet forge well have a 12" chimney. The smithy is made from 2 x 4s and T-111 outside,inside is cement board ceiling with corrugated steel on walls. Floor is gravel,the smithy is off the ground about 3" all the way around except at the doors and 10 cement pillars. The smithy is also completely insulated with R-13.

How would I go about ventilating and how much air will I need.

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All the ventilation you can get, and then some.

You are designed to breathe air, that stuff with no smell, no taste, and that you can not see. In a small area with only one opening pollutants can build up quickly, whether from the forge, grinding, torch work, plasma, etc.

Move the gas forge to the door or outside.

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The insulation  seems to indicate a possible "tight" situation.  RUN get a Carbon Monoxide meter/Alarm.  Ventilate till there is not CO issues with the propane forge going full out!  You may want to investigate infrared heating that will keep you warm even with high air flow.

 BTW a "3 burner propane forge" is NOT a specific size I've see a 3 burner unit as large as your smithy in an industrial setting.  For my 2 burner propane forge 10" diameter shell 14 inches long I generally run it in a 20'x30' shop with 10' walls and two 10'x10' roll up doors open and with open gables.  CO exposure is cumulative to a point.

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I'm very sorry I don't have a huge shop mine is only 8' x 12' rollup doors and 20' ceilings I don't have. It seams that you only can help pro's and the little guy gets answers that they have no way of using. I was told this is wear to go for good info but I can't see any help. I have read like I was told after my first question and found very little to answer my questions now I ask and get told of a bigger shop and all the air I can. I really thought that this forum was here to help the new guys get started I guess I'm wrong again thanks for the help.

Stop making accusations and read what was written not  what you imagined

 

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I'm sorry but my answer was for a small hobby shop. Will anyone cry if you accidentally kill yourself?  I've know folks who have come awfully close with propane forges---as in passing out as they try to exit their small shops.  Can you point out in your original post where you listed the wall height and the roll up door size?  HOW WERE WE SUPPOSED TO KNOW IT THEN?

Are you mad at us for not knowing information you didn't supply?  We tend to err on the side of safety here; but it's for good reasons.  Many of us have made the mistakes and paid for them---sometimes with very expensive medical bills and at least for one of my friends; death.  If we had been speaking of professional large shops we probably would have just directed you towards the OSHA regulations.

I can personally say having lived 15 years in Ohio that when working when it's cold  the tendency is often to want to not ventilate properly and "enjoy the forge's unvented propane heater side effects.  Shoot I got a CO headache once at a SOFA meeting when they closed the doors up a bit as there was a blowing rain storm going on outside.

Hope to meet you at Quad-State with both of us alive and kicking!

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Harry: I'd love to help you but I don't know what you're looking for. Good ventilation and a CO monitor is THE answer. Thomas has a modest sized shop and it's not air tight. He brought it up so YOU would know where his experience is coming from currently, NOT to tell you to build or get a bigger shop.

He made some valid observations based on the information you gave us and pointed out some of the issues with it. At that point he pointed out that even in his much larger shop opening opposing roll up doors, the man doors and windows was just adequate.

How much do you know about CO, (Carbon Monoxide)? Are you aware CO binds to hemoglobin 30x as rapidly and strongly as O2? This makes it VERY dangerous and cumulative, it takes days to flush from your system unless you have access to a hyperbaric facility.

You have an evidently very tight shop with a forge that produces a LOT of CO not to mention the other combustion byproducts while consuming oxygen. Without knowing what kind of ventilation you have running all any of us can do is provide a conservative answer. More ventilation is better even if it means wearing heavy clothing in winter or just stopping operations if it's too cold.

I have a 30'x40' red iron shop with 14' eves a 16' roll up door and only one man door. It's unfinished due to my accident in '09 so it's uninsulated and far from air tight. Running 2 burners is enough to make a person feel the CO in about 4 hrs. The meter says it's not a good place to be in for very long.

I tell you that not to say neener neener my shop is bigger, or you should get a larger shop. I tell you so you'll have an idea of what two, properly tuned 3/4" naturally aspirated burners will do to the cross ventilated atmosphere of more than 16,800 cu/ft.

I don't know what you want, I have doubts you know. Complaining that we aren't answering your vague question in the way YOU want isn't a productive attitude. If you'd like a short answer how about this one? Move your forge outside or get an induction forge. How about this one? Install forced ventilation that will exchange the entire volume of air in your shop every 2 minutes. Maybe get a supplied air breathing mask or hood?

Failing adequate precautions for your unspecified situation, have at least enough life insurance to cover your funeral without burdening your friends and relatives.

Frosty The Lucky.

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Unfortunately there are a lot of variables that you haven't defined carefully enough to allow reasonable suggestions.  Glen, Thomas and Frosty were clearly trying to be helpful by indicating where we need additional information and/or how they solved these issue themselves.  If you would prefer to do the code required ventilation study and get a professional engineer onboard (at an average of $120/hr.) I'm sure you could hire a consultant locally.

That being said I'll try to give you some feedback based on assumptions I'm making about your shop (I will be getting a little technical, so bear with me):

  1. You don't run the coal forge and the gas forge simultaneously
  2. You have at least a 3' x 7' door that you can leave open
  3. You are burning propane in your gas forge, not natural gas (like I do)
  4. Your 12" chimney draws well and removes all visible smoke when coal forging

My recommendations would be as follows:

  1. Get a $35 Fire/CO monitor from your local big box hardware store.  There is no substitute for monitoring
  2. For coal forging you're probably fine for ventilation with the door left wide open during forging and the chimney exhausting the fumes, forcing the replacement of air at that point.  You may want to add an exhaust fan (see below) to draw some heat out of the facility as well, but be careful to not overcome the chimney effect and draw your fumes back down the chimney (best to keep the door open most of the time you are forging and start the exhaust fan only after the chimney is drawing well).
  3. Gas forging is another problem, as you likely don't have a hood to capture the heat and drive the exhaust up a chimney.  My recommendation is to install a propeller style exhaust fan at the high point in your building.  A good rule of thumb is to design for a minimum of 10 air changes per hour (10 ACH) for ventilation.  That is 10 full room volumes per hour (i.e. if you have 10' ceiling height in a 8' x 12' shop you need at least 160 CFM of ventilation air, not a whole lot.  For my 20 x 20 shop with a peaked roof above 10', I have a 24" exhaust fan that pushes over 3,000 CFM with a 1/2 HP motor, but I like lots of air exchanges for both safety and cooling).  However you also need combustion air entry added to the mix for consideration.  Typically code states that this air must enter the room at two points, one high and one low.  In this case you can get the high entry via  a roof vent (I use a turbine style in my shop) and the low via the open door.  The national gas code requires that these openings be at least 1 sq inch in size for each 4,000 BTUH of heating capacity of your fuel burning appliances.  If you know the ratings on your burners  you can size this accurately, but likely an open door will do for the lower one and a 12" turbine vent for the upper.

Anything more and I'm sending you a bill ;)

Turbine vent:

roof-turbines-1855-roof-ventilation-turb

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Ok, am I reading it correctly that you have a 3" gap between the wall and the gravel floor? If I read that right, that would handle the low air intake requirement. 

Lets address who answerd you, other than Frosty, they all have day jobs, well paying jobs ($50 an hour or more!) infact the last gentalmn design a ventilation systems for a living. 

We  get many young men who feel that the world owes them something. These gentalmen obviusly think you are worth their time, we have spent an $50 on your question. So, let's loose the attitude and read what has been write  and not what you think was written, not what you think was writen. Most of us who take the time to answer new member questions are your parents, grandparents and great grandparents age. We do not react well to entitled child like tantrums. 

 

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Actually I checked his profile, and while I would also attempt to help the young folks who are trying to build a safe, successful smithy the OP is apparently in his 60's.  I think this is just a matter of miscommunication.

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Then I offer my heart felt apology for my tirade. 

Other the draft around the ankles, a 3" gap sounded like a simple salution to the ventilation issue. 

I also like Steve's roof vent, he has a coupula with a fan. Hiden, clean and attractive. Infact his shop isn't any larger than the one Mr. Robinette is using. Nice coal forge and a monster gasser for heat treating small swords. Then again he is just to meen to die ;-) 

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3" gap can get covered by snow on a regular basis in Ohio in the winter.  I used to forge in the snow at times when I lived there. Preheating the anvil and tools and standing on a piece of plywood to keep the feet warm were the biggest things I learned.

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I've had to get to a drilling rig out near Roll OK in a blizzard  before---they were dropping hay for cattle from the air, (never saw so many pheasants in my life! each bale impact zone was crowded with them.)  Why we even get snow in El Paso! ISTR that at least oncet it actually *covered* *the* *ground*!  but it was gone the next day...We'll take precipitation most anyway we can get it though hail is not real fun...

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On 8/13/2016 at 11:39 AM, harry robinette said:

I'm very sorry I don't have a huge shop mine is only 8' x 12', rollup doors and 20' ceilings I don't have. It seams that you only can help pro's and the little guy gets answers that they have no way of using. I was told this is wear to go for good info but I can't see any help. I have read like I was told after my first question and found very little to answer my questions now I ask and get told of a bigger shop and all the air I can. I really thought that this forum was here to help the new guys get started I guess I'm wrong again thanks for the help.

 

 

On 8/11/2016 at 0:32 PM, Glenn said:

All the ventilation you can get, and then some.

You are designed to breathe air, that stuff with no smell, no taste, and that you can not see. In a small area with only one opening pollutants can build up quickly, whether from the forge, grinding, torch work, plasma, etc.

Move the gas forge to the door or outside.

I made the first post to answer your question. All the ventilation you can get, and then some. and Move the gas forge to the door or outside.

IForgeIron is the place to get good information, but you have to be receptive to the information you are given. The replies came from folks that KNEW what they were talking about.  One of the folks designs ventilation systems for a living. 

8x12 feet is only 3 sheets of plywood large and I suspect that the walls take up part of that space. It is too small (in my opinion) to run a 3 burner gas forge without good ventilation. The bad air will hide in the corners as well as inside the building unless there is a LOT of cross ventilation, which is why I said to move the gas forge to the door or outside.

I suggest that you reread the thread with an open mind, paying attention to the advice given. Take the information to your shop along with a CO detector and test it out. No matter what the numbers are on detector, err on the side of caution, staying out of the hospital, and going home to the family at night. Headaches, dizziness, body aches are all indications your already in trouble and is your body's way of telling your brain you did something stupid. We all have taken short cuts, and chances, and it is site policy to warn ANY member if we see that they are doing something that may cause them harm. We can not keep you safe, THAT you YOUR personal responsibility. 

Get mad if you want but I do not wish to send get well cards to the hospital, or condolences to your family. Please, PLEASE, use caution in what you do, and how you do it.

 

 

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Harry sir My first forge area was an 8' x 8' shed almost killed myself with carbon monoxide. Never again. The next was  8'x8' 3 sided shed' The next was a 3 sided 40' x20' loafing shed with push out openings on the north (downwind side). Currently I am using a 12' x 16' awning never again will subject myself to carbon monoxide poisoning It is the worst headache one will ever experience. I hope you are still around to read this response. Welcome aboard we are here to help you have a good experience

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Guys, if it helps at all, let it be known that I've taken your input to heart and have accommodated my design for the lean to I'm planning off the back of my shed.  I've been struggling with how much I should button it up.  Deep down I want to insulate the space my side blast is in because it is water cooled.  Reality is that I'm just going to have to figure out how well it does with freezing.  I'm not interested in having my wife and kids find me dead in the back of my shed.

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Insulation has advantages, like reducing condensation dripping of the celing, heat radiating down off the bottom tin etc. just ventilate. 

Maw to freezing, if you cover the sump/bosh to keep critters out you can use automotive antifreeze, look for the less toxic brands. Stuffs a neurotoxin for cats so make a vented lid to keep them out, or your vet will be main lining vodka into fluffy. 

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How about those plug in pipe warmers?  And thank you for not getting bent out of shape and leaving before we could hammer those bents out...

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I'm also concerned that, if I insulate and make a warm, cozy space, every critter for miles around will find it an amenable holdover for the winter as well.  Also, I don't have power running to my shed.  My intentions are to run a heavy gage power cord from a dedicated 20amp outlet on the side of the house.  I only need power for my lights, my blower and maybe a radio.  I plan on doing my finishing work in the garage.  

I'll look around for antifreeze solutions as well.  I'm still chuckling a little about Charles' choice of wording..."Mainlining vodka to Fluffy".  The real sad part is that the stuff tastes good to them.  I've heard of people purposely putting it out for their neighbor's pets simply because they didn't like animals.  There are some sick people in this world.

EDIT:. I just did the research.  Apparently using propylene glycol instead of ethylene glycol makes antifreeze more effective and nontoxic.  I guess they had difficulty finding a way to mix it in solution until recently.  One brand that sells the new stuff is Sierra.  Propylene glycol is also a food additive I won't even have to feel bad draining my tank!

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well that is the treatment, Ethanol has a preferential uptake over the antifreeze so if they can keep the critter right at the edge of alcohol poisoning it has a chance of surviving.

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Thank you everyone for the helpful information. I've been reviewing this thread in anticipation of constructing my shop at home. I anticipate setting up for a coal forge with hood, propane forge (blown burner, approx. forging area 17" x 6"), and a small woodburning stove inside a shop that is 10ft x 20ft with 10ft peaked ceilings. The building size may be modified, but that is my current plan. I don't anticipate insulating the building, which will be wood frame on a concrete pad.

If I'm following the discussion correctly, Latticino's comments in particular, I'm coming up with the following calculations: I would have a room volume of approximately 2000 cubic feet (though I appreciate I'm not yet allowing for the peak space). To allow for 10 ACH I would need a fan of at least 333 CFM (2000 cubic feet/ 6 = 333.33). This coupled with adequate lower ventilation (i.e., open doors/windows) should allow for appropriate ventilation. Does it appear that I am tracking/calculating that correctly?

If so, it appears to me that a fan such a this Master Flow 1500 CFM would be more than adequate. Does that seem like a reasonable choice? Thank you in advance for any input.

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Welcome aboard Lutz, glad to have you. Yes, you're tracking the air replacement numbers close enough for gvt. work. . . I THINK.  Figuring the volume of a peak is as easy as height x 1/2 W. x L.  Where height is eave to peak and 1/2W is from the peak to the outside wall. Makes it a rectangle.

Frosty The Lucky.

 

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It might be cheaper and more efficient to look into the setups greenhouse owners use to ventilation.  Inline centrifugal fans combined with targeted duct work would work.  Then again, the fan you linked would be an easier installation....look at me second guessing myself!  Simple test.  Try out the fan you chose and run a CO detector in there at head height with the forge going for a few hours.  That's what I would do.  

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I am not a ventilation professional.

I read that the Fire Brigade find it is quicker to use positive pressure ventilation to clear a building of smoke and fumes than to use the same size fan as an extractor.

This is on the basis that every cubic metre of air moved by the fan is a cubic metre of fresh air into the building. Used as an extractor, the fan is moving mainly smoke to start with, but then every subsequent cubic metre is a mix of fresh air and smoke, so it is much less efficient.

I also found that positive pressure ventilation has three other advantages for the forge.

If you have a flue above your hearth, positive pressure assists the flow of smoke and fumes up the chimney. An extractor fan in the wall will have the opposite effect.

It has the effect of blowing any sound back into the forge which may help reduce any noise problem for your neighbours...think of the way sound carries downwind rather than upwind...

I set mine up so it blows fresh air directly onto us working on the hammer or presses.

Alan

 

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Thank you all for the greetings and the input!

Alan, My limited understanding on positive pressure systems is that you are creating an area of increased pressure in the shop by forcing air in via fan, and it then naturally evacuates to outside the shop which is of a lower pressure. I would imagine you facilitate this exit of air at the roof level with something like a turbine vent illustrated by Latticino above. Am I thinking in the same terms as you are? If that's the case, the question I have is, how do you calculate your CFM needs? If you have a large diameter turbine for exhaust, can you base it on the CFM of your fan inputting air in the shop and be confident in the ACH being provided?

As I'm talking it through, it also seems like it may make good sense to simply have a mixed system, with both powered intake and output that could be used as needed, though I'd still be interested in thoughts on the above questions. I plan to run a CO detector regardless of my configurations. 

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