New forge! Now, need to vent (CO1 issues)

[Tom W.]

So I got a small hand-pump forge and it works great. I wanted to be able to make a hood for it and vent it out the existing chimney in my garage. The problem is that for now there will be two 45 degree bends to get to the chimney. My carbon monoxide alarm went off every 20 minutes or so. I just couldn't get enough draw up the vent to pull all of the exhaust. So now I am looking for input from other members. Would a straight run up through the roof be substantially better? Perhaps should I employ a fan?

Here's the wood-burning stove leading to the chimney:



Here's the forge when in place with the metal hood:



Railroad track anvil:

[Pat Roy]

Tom

What is the size of your smoke pipe? Are both the forge and wood stove burning at the same time? How big is your chimney? I suspect you are trying to stuff too much into one flue and/or your pipe is too small. CO is nothing to fool with. You need good draft. I have an eight inch pipe and with an essentially straight run it is barely enough. The height of the chimney is important too.

[jeremy k]

Most people would recommend at least a 10" and 12" to be optimum. There are those that get by with less than an 8" flue, I've seen a few, but they are only doing very small forgings with a small fire to keep it drawing fairly ok. A stand alone flue would be your best choice.

[MattBower]

I'm no expert on this subject, but this has come up here before. Guys with experience -- and who actually use solid fuel forges regularly -- seem to recommend chimneys in the 10"-12" diameter range.

Oh, and side draft seems to work much better than an overhead hood. If you're stuck with the hood it's probably even more important to go quite a bit bigger than what you have.

[Marksnagel]

As is commonly mentioned concerning gasses and ventilation, do you have adequate air coming into the garage? We have beat the poor horse slam to death before in regards to a forge in the house basement, so here goes again. Is your garage attached to your house?


Tom, if you haven't read through this post please do so. It may help.
http://www.iforgeiron.com/topic/24921-small-charcoal-forge-indoors/page__p__251213__hl__ventilation__fromsearch__1#entry251213

I am not insinuating that you are endangering yourself or your family but I just want you to be as informed as possible in regards to the dangers of gasses from forges.

Be safe.

Mark <><

[Glenn]

Do not share the chimney. Hoods are not efficient. You have to have more air coming into the shop than what can go out the chimney.

Many of the forge/chimney issues have been covered before. 6 inch chimney pipe is just too small, 10 inch or 12 inch diameter is recommended. I use a 24 inch diameter (2 feet in diameter) chimney, which was built to FIT the 55 Forge I use.

You need to add about 3-4 gallon of coal to that fire. You do not have enough fuel to get a good heat on the metal.

[ThomasPowers]

For a forge that small make a total enclosure with just the stock opening in front and a mousehole in back for long pieces. That hood is getting mostly cold room air and not hot forge gasses Restrict it so it gets all the forge exhaust and as little room air as possible.

[Ted T]

There is a lot to consider when installing a chimney.
Quick rule of thumb: 8 inch Diameter pipe would be the minimum I would ever go.
And that is only if I had a straite shot up with no bends.
And then I would want to extend it as high as I could above the pitch of the roof.

As Jeremy suggested, use 10 inch or 12 inch diameter pipe for good flow.
No bends allowed.
I have seen all kinds of configurations of chiminey's. Some small diameter pipe with a couple of bends with a booster fan . . . . on and on!
Most I would not trust! - - It can be deadly if you take a risk type of a short cut.
I would error on the safe side everytime!!!! Hard to forge when you are dead!

Here are some chimney installation considerations to think about.
But your Local Codes will be the bottom line of how you should do it.

Chimney Height
First I suggest that you check your local codes.
But the general rule of thumb found throughout the country at one time, as follows.
Chimney height Rule: 10’-2’-3’
This information is from an old file what I had accumulated and used years ago when I was active, but I would bet it is still valid.
The Factory-built fireplace manufacturers specify minimum and maximum chimney height. Woodstove manufacturers may have similar requirements. Both types of appliances and most codes require the 10 foot/2 foot/3 foot rule for minimum chimney height above the roof:

The chimney must extend at least 2 feet above any portion of any structure within 10 feet (measured horizontally) AND must extend at least 3 feet above the highest point of its roof penetration.

The height of the chimney must meet or exceed both of the minimum requirements. If manufacturer requirements exceed code minimum height requirements, they should be followed.

These minimum heights may have to be exceeded, however, for adequate draft and satisfactory performance.
Additional height can help improve draft and may make the difference in marginal situations.
It will not, however, cure severe draft problems. There are two situations that call for specific attention to chimney height:

Heated portion of the structure above the top of the chimney: the structure can act like a chimney and compete for the air supply. This action, called structure stack effect, can result in weakened draft or even smoke spillage into the structure.
High altitude: Your forge may need stronger draft to deliver a greater volume of air at higher altitudes to make up for the lower concentration of oxygen.

Recommended sea level chimney height may need to be increased by 2-3% per 1000 feet of elevation.
In general, a minimum venting system height (chimney or for some woodstoves, chimney + connector) of 15 feet is recommended. It should be noted carefully, however, that too tall a system can cause over-drafting problems for wood stoves, but would most likely be desirable for most coal/coke forges.
This issue seems simple, and maybe it is to a person who is well informed - - - So please study and be fully informed as you procced.!

[Tom W.]

Thanks for all the input folks. I ended up bed-ridden soon after I posted this.

The stove and forge/hood never shared the pipe. The pipe was 6 inches. The chimney is plenty big. The hood over the forge was a prototype and it proved that it would not work.

I can still drag the forge outside but here in Minnesota that's about to become a pain.

I am willing to run a straight pipe up through the roof. I will start looking for 12" piping. I have a handyman pal who can help with this.

I am not insinuating that you are endangering yourself or your family but I just want you to be as informed as possible in regards to the dangers of gasses from forges. Be safe. Mark <><

Ha, no problem. I certainly AM endangering myself. At least I had the common sense to have the CO detector out in the garage. I was able too open the door and put a fan outside blowing in. But once it's 0 degrees, that will be very oncomfortable. For now I am going to drag the forge outside.

I aslo heard that providing the forge with a rich source of oxygen (outside air) may help the fir burn clean.

[Kendall P]

Glen and Ted really summed this one up well, a proper extraction system for your forge is really something that you should not try and save money on if you plan on useing it in a building. Sometimes you just have to bite the bullet if your serious about doing something.

[SmoothBore]

This "wheel" has already been invented.

A small, inexpensive "Squirrel Cage" exhaust fan, mounted at the chimney opening, will resolve all your issues.

It looks like you're using 6" stovepipe, ... so an 8" Squirrel Cage, that's about 3" or 4" wide, will move plenty of volume.

( I'm sure Grainger's has something that would work just fine, ... or if you're inclined to cobble up something on your own, ... the fan out of an old range hood, would get the job done. )


.

[Tom W.]

This "wheel" has already been invented. A small, inexpensive "Squirrel Cage" exhaust fan, mounted at the chimney opening, will resolve all your issues. It looks like you're using 6" stovepipe, ... so an 8" Squirrel Cage, that's about 3" or 4" wide, will move plenty of volume. ( I'm sure Grainger's has something that would work just fine, ... or if you're inclined to cobble up something on your own, ... the fan out of an old range hood, would get the job done. ) .

You mean mounted at the top of the chimney?

I am willing to put in a proper exhaust system. This was a prototype that failed.

[SmoothBore]

You mean mounted at the top of the chimney?

I am willing to put in a proper exhaust system. This was a prototype that failed.

The ones that go on top of the chimney work great, ... but are a bit pricey, and an unnecessarily complicated solution, to a very simple problem.


But the fan I was referencing, was your garden variety "Squirrel Cage" fan.

These fans normally have a square, ( or rectangular ) flat flange on the discharge, ... that can be bolted right into the chimney, at the point where your existing stovepipe enters now. ( A simple gasket, or caulking, will seal the joint. )

The inlet for these fans is usually a round venturi, that enters the fan housing, so that the air enters the center of the squirrel cage, at 90 degrees to the discharge.

You should be able to rotate your existing 45 degree elbow, that now enters the chimney, ... so that it is turned toward the stud wall, that is showing in the first photo.

With it turned that way, it should plug right into the venturi of the Squirrel Cage Fan.

If you google "Grainger" and then search that catalog, using the keyword "Squirrel Cage" you'll see lots of pictures of the type unit I'm describing.

OR, for under $30.00 ... Home Depot has a 6" in-line "duct booster" fan, that goes right in the stovepipe, ... that will most likely be adequate.

Many years ago, I used one of those little "in-line" fans, on the stack of a small, gas fired re-melt furnace, that had draft issues.

It proved to be a simple, effective solution.


Mod note: Make sure all parts are metal, as plastic will melt





.

[Drewed]

.....OR, for under $30.00 ... Home Depot has a 6" in-line "duct booster" fan, that goes right in the stovepipe, ... that will most likely be adequate.
...

No, don't! These are plastic and melt! Trust me, I melted mine. And mine was at the top of my chimney!

[SmoothBore]

I stand corrected, ... the Home Depot unit is not for exhaust.

So, I looked in the trusty "Grainger" site, and found :

In-Line Draft Inducers
Increase draft for gas- and oil-fired heating equipment.
Variable draft control. Aluminized steel
housing and wheel. 115V, 60 Hz.
Fastening band included, except bandless screw
attachment on Nos. 4C730 and 4C731. Uses: For
long, horizontal vent connectors, undersized chimneys,
and structures with a slight negative pressure.

These units are around $125, and require no other modifications to your chimney.


I'm sure any HVAC supplier can fix you up with a similar unit.


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[Rich Hale]

The smoke from a coal fire seems to be a wee but different thtan the discharge fro oil or gas. I am not going to look up the contents and post them here as I am pleasinglly tired from along day in the shop,,,my point is I do not think an in line fan will work in discharge piping of products of coal smoke. I can almost envision a y of some sort that would privide forced air to move things along. But I have no experience with that kind of hook up. A propperly set up and drafting forge using coal can work without a fan.
AND if your illness is related to CO poisoning you must remember that the changes made in your body from that are not healed for several days and will accumulate if you are exposed again soon. SO a repeat acute injury is highly likely and for sure may be worse than the first.
REview all of the posts on here that will help you with getting this right. Think a lot about changes and seek on site help from someone knowledgeable if youi do not for sure know that your changes will solve this puzzle.

[Tom W.]

I lowered the hood over the forge so the smoke and gas goes up nice. No more CO alarm sounding.

Now I have to practice identifiying the critical temp of 1095 as I have been missing with my hardening attempts.

[ThomasPowers]

Deeper fire! If you are using wood/charcoal set a couple of firebricks on their sides to make a 4"+ deep channel to help keep the fire deeper! *ALL* the fuel being in the forging area then.