This is very troubling to me. I just read in a book that galvanized stovepipe gives of toxic fumes when heated to high temps(750 or over). Well, my internal flue gas thermometer sometimes reads above 1,000 degrees. Yes, for short periods at relode before closing bypass, but whenever it gets up there, I smell a nasty smell. I got the stove last year and in the beginning, I always thought it was the paint still curing, but then it never went away. It happens every single time that pipe gets hot. So, after reading what I just read, I checked out the pipe I have- Simpson Dura-Vent DVL (Which is their double wall pipe). From what I gathered on the Simpson website, the inner wall is stainless, and the outer wall is galvanized steel painted black. There is about a 9 foot exposed interior run of this. Those high flue gas temps are hot enough to get that outer wall piping hot. I have two young daughters, the younger we just brought home from the hospital less than three weeks ago. Why would they sell this? It bothers me right down to the bone this could have been harming my family all along. I posted this as a warning for others. I'll be contacting the dealer about this. It was very irresponsible not to warn me of this. Does anyone have any suggestions? Does anyone know of any black double wall pipe that is not galvanized at all?
Toxic Fumes! Please Read!
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I have took alot of scrap metal off my farm and I know Galvanized pipe is toxic when you cut it or burn it it puts off a yellow smoke I wouldnt think your gas stove or furnace would put out those temps I am sure that pipe has a UL rating or something so it is safe I have seen 30 year old houses with galvy pipe. check your therm. or do more reading. I really dont think you should be getting those temps out of a stove that is rated for galvanized pipe anyway but hang around and youll get an answer
I really doubt that the exterior of a double wall pipe exceeds 700. I agree that it is probably the paint or other oils, and not a dangerous galvanized burn off.
I have simpson rigid double wall duraliner, no problems here, after 3 years still breathing & bitching. 
The pipe is connected to a woodburner- Avalon Arbor. With the flue gas getting to 1100(it's been over 1200 a few times), I'm sure that inner wall is darn near 1100 too, so I would think that outer wall could quite easily get over 700, especially with a 500 degree stovetop right below it heating it up. The pipe is UL listed, and I certainly havn't seen any yellow smoke. It makes me feel a little better having some people here tell me it's probably not as big as I'm making it, but I do get that smell every time those temps go up. After a full year of serious burning, I strongly doubt it can be paint or oil anymore.
Relax, I think what you read was misleading.
Galvanizing processes can vary, but at they basically involve creating a zinc alloy. With double wall pipe, you are probably not reaching 750 degrees for a couple of reasons. First, you would need more than 2 inches clearance to combustible at those temps. Second, you would be in danger of melting your pipes if you are, since galvanized steel melts around 785 F. These fumes you mention are generally a concern during welding - and you need to be near the boiling point to create fumes (over 1600 F). I am betting you are smelling the paint.
(broken link removed to http://www.abtdrains.com/f/msds-galvanized-steel.pdf)
Pete
Galvanizing processes can vary, but at they basically involve creating a zinc alloy. With double wall pipe, you are probably not reaching 750 degrees for a couple of reasons. First, you would need more than 2 inches clearance to combustible at those temps. Second, you would be in danger of melting your pipes if you are, since galvanized steel melts around 785 F. These fumes you mention are generally a concern during welding - and you need to be near the boiling point to create fumes (over 1600 F). I am betting you are smelling the paint.
(broken link removed to http://www.abtdrains.com/f/msds-galvanized-steel.pdf)
Pete
Welding or using a cutting torch on galvanized will heat it to the point that it puts off toxic fumes, but you are not likely to see a problem from your stove pipe - especially the exterior wall of a double wall pipe. Your body does not react to galvanized fumes like it would to CO fumes or something like that - Exposure would result in what is called metal fume fever and it is from breating the zinc fumes galvanized puts off at very high temps. If you or your family were to be exposed, you would be sick as dogs. Irritated eyes, noses, throats and nausia. Also, as far as I know there are no known long term health effects so at the very least rest assured that you have not damaged the health of your family and replace the pipe if it will let you sleep better.
"The poison is in the percentage." Concentration, duration of exposure, and frequency, are all important considerations when evaluating "toxicity".
Remember well, water in the proper concentrations and duration of exposure is extremely toxic. The smoke that you smell each time you load your wood burner is far more toxic and dangerous than a little smell for a minute or two off your smoke pipe.
I've smelled the same smell off the smoke pipe connected to the wood/coal boiler. The galvanized metal has turned gray in a few spots where it's burned off. The area of the basement where it is has a pretty decent breeze blowing through it most of the time anyway... and it's very short duration and low exposure.
Like picking up a 25 to 60 ppm reading on a CO detector... your nose will smell things at levels way below where they'd hurt you, and then there's other gasses that don't have an odor.
If you're really nervous about it, replace it with black...
Remember well, water in the proper concentrations and duration of exposure is extremely toxic. The smoke that you smell each time you load your wood burner is far more toxic and dangerous than a little smell for a minute or two off your smoke pipe.
I've smelled the same smell off the smoke pipe connected to the wood/coal boiler. The galvanized metal has turned gray in a few spots where it's burned off. The area of the basement where it is has a pretty decent breeze blowing through it most of the time anyway... and it's very short duration and low exposure.
Like picking up a 25 to 60 ppm reading on a CO detector... your nose will smell things at levels way below where they'd hurt you, and then there's other gasses that don't have an odor.
If you're really nervous about it, replace it with black...
Thanks for the replies. I definitely feel a lot better. I guess I'm protective over my little girls. Pete- Thanks for the link, it was very informative and helpful. The book I am reading states- "Another good cautionary from the Guild(NCSG) : don't use galvanized stovepipe in a woodstove installation, because it gives off zinc vapor, which is toxic, at temperatures of 750 degrees Fahrenheit and higher."
One thing I don't get, how can steel melt at 785? A lot of people get steel stoves up to those temps. Why would galvanized steel melt before others?
Also, if it is the paint, how can that still be smelling after all those times I've heated it way up?
Leon- I'm not sure what the rest of that last line should be. black what?
One thing I don't get, how can steel melt at 785? A lot of people get steel stoves up to those temps. Why would galvanized steel melt before others?
Also, if it is the paint, how can that still be smelling after all those times I've heated it way up?
Leon- I'm not sure what the rest of that last line should be. black what?
Im a professional welder. If you where breathing zinc fumes you would defenitly know it. Its just like the flu. Puken and dizzy headache cant see straight ive had the fever my share of times
You know what I have a problem with understanding, "How does the snause , erhh, nose become the teller of toxic exposure. If that is the judge, going by a diaper pale should kill is all. Every day we are exposed to toxins. The amazing thing is the human body is equipped with a lot of defenses. Because it stinks doesn't male it toxic. Just the same the sweet smell of almonds doesn't let you know there is a toxic poison behind it.
Zinc is everywhere. It protects a lot of things from rust. Do you stop breathing when you cross the Golden Gate Bridge? Did you stop using your SUV, with the body guard, for fear of getting a whiff of toxic fumes? Well, don't fill your fuel tank with gas, cause the fumes will get you, don't go to the fabric store and buy any treated fabric for fire proofing or waterproofing.
You can get fired up about your environment issues with little or no fact. Check the facts, most are empty, or over ruled by other daily exposures.
Zinc is everywhere. It protects a lot of things from rust. Do you stop breathing when you cross the Golden Gate Bridge? Did you stop using your SUV, with the body guard, for fear of getting a whiff of toxic fumes? Well, don't fill your fuel tank with gas, cause the fumes will get you, don't go to the fabric store and buy any treated fabric for fire proofing or waterproofing.
You can get fired up about your environment issues with little or no fact. Check the facts, most are empty, or over ruled by other daily exposures.
Black pipe... replace it with black pipe, or you could put stainless in...
Then, someone else is going to flip out over the toxins in the paint, and the smell, and write an article about the nasties in that. Stainless gives off it's own oxides if you heat it hot enough.
That said... would I run a hundred feet of it through an airtight room and heat it to 800 degrees and sit in there and read? No. Wouldn't have my kids sleeping in the same room with it either.
Then, someone else is going to flip out over the toxins in the paint, and the smell, and write an article about the nasties in that. Stainless gives off it's own oxides if you heat it hot enough.
That said... would I run a hundred feet of it through an airtight room and heat it to 800 degrees and sit in there and read? No. Wouldn't have my kids sleeping in the same room with it either.
LeonMSPT said:
Gray is not the color of burned zinc. White or yellow residue is evidence of having burned the stuff. I doubt you've burned the zinc. I'd think it would be hard to do to the outer wall of a double-wall pipe.
woodburn said:
Steel doesn't melt at 785, but zinc would burn. The concern is the fuming zinc, not melting steel. But that's for a single wall, not an outer wall like yours.
woodburn said:
It isn't the steel melting at that temperature, it is the outer zinc layer that melts.
EDIT: Jinx
Single wall galvanized smokepipe, that's changed color. Nothing was spilled on it or got on it. Was "galvanized" appearing, now splotches on it have turned gray. The top side of one elbow and the top of a slanted run, the hottest areas.
If the zinc didn't burn off, changing the color of the pipe, what happened?
If the zinc didn't burn off, changing the color of the pipe, what happened?
littlesmokey said:
And maybe the finest example...the white cream commonly used directly on the noses of lifeguards and the like to prevent sunburn - zinc oxide. Right under...er...on our noses.
If it isn't burning it isn't releasing dangerous fumes, so no problems for the nose to detect. Were the golden gate to catch fire, any survivers who huffed the yellow smoke on their way to surviving would be doubled over sick.
The nose doesn't determine toxicity, it is mearly a warning that "hey, this does not smell like it will be good for you", just as the sense of smell can trigger the opposite reaction when it picks up a desireable food item or...ahem...the scent of a woman (insert WHOOOOAHHHHH here). The nose isn't the "teller of toxic exposure" per say, but it is a relatively reliable indicator and first line of defense (with few exceptions for odorless toxic gasses) when there is something in the air you shouldn't be breathing. After all, it is the nose that the toxins have to pass through before they get to do their damage to the rest of your body. It makes sense our smell has evolved to detect many of the toxins that would kill us off if we didn't know we were breathing them.
LeonMSPT said:
Wow, single wall galvanized is a pretty bad idea for a woodburner. I'm no scientist, but I suspect the zinc might be oxidizing faster without reaching the point of burning off entirely. The whole point of zinc plating is that the zinc oxidizes first, before the steel. If that's the case, then it wouldn't be as high a concentration of fumes as burning it. My experience with zinc plated metal is welding, and I've only seen fuming when cutting or welding. You can see the edge of the heat affected zone on galvi because that's where the powdery stuff ends. I'd sure think about replacing a single wall galvi smokepipe.
I considered it. Don't know really... the hottest and most likely areas to burn off are already burnt. When the wind blows, you can nearly fly a kite in the area of the basement where the boiler is. Did notice for a few days when it was new, an odor that wasn't wood and wasn't paint. Didn't feel bad, so to speak, maybe not great but not awful.
How much does it take to get sick from it? Obviously it's not, "One sniff and you're a dead man."
Need to add a barometric damper, and considering piping the entire thing with T's to allow cleanout without taking the whole thing down and apart yearly. Also allow me to inspect the inside periodically by removing the covers...
If I do this, I'll use black pipe. Thought about stainless, and if money were no object I'd do it in a heartbeat.
Might see what my cousin has laying around for takeouts and mistakes... maybe I can get a deal?
How much does it take to get sick from it? Obviously it's not, "One sniff and you're a dead man."
Need to add a barometric damper, and considering piping the entire thing with T's to allow cleanout without taking the whole thing down and apart yearly. Also allow me to inspect the inside periodically by removing the covers...
If I do this, I'll use black pipe. Thought about stainless, and if money were no object I'd do it in a heartbeat.
Might see what my cousin has laying around for takeouts and mistakes... maybe I can get a deal?
LeonMSPT said:
Sure. It makes you sick, not dead. Plus, you're not standing over it all day. At this point it's only an issue if you overfire. Maybe you'd just replace those hottest sections when they get worn out with black or stainless and leave the rest.
galvie pipe should never be used to vent a woodstove , replace any galvie pipe you may have with the proper black stove pipe minimum 24 guage thickness.
NFPA-211 chapter 12.4.1.2 specifically states "galvanized steel pipe shall not be used for solid fuel burning appliances"
EDIT reread your post , the code stated above applies only to single wall pipe , sorry if i spooked ya.
NFPA-211 chapter 12.4.1.2 specifically states "galvanized steel pipe shall not be used for solid fuel burning appliances"
EDIT reread your post , the code stated above applies only to single wall pipe , sorry if i spooked ya.
Thanks for the edit stoveguy. I am glad mine is double, but still, having the zinc on there isn't a great feeling. If we've determined that the fuming starts to take place around 785, does anyone agree that that outer layer can be reaching that temp. under the following circumstances:
Flue gas thermometer 18 inches above flue reads 1100. This means it must be even a little hotter lower down.
Stove top surface temp 500.
At the stovepipe adapter and bottom section of pipe, can't that outer layer still be close to that 785 temp? I will put my magnetic thermometer on there to check, but I think these pipes should not be galvanized even with double wall.
Flue gas thermometer 18 inches above flue reads 1100. This means it must be even a little hotter lower down.
Stove top surface temp 500.
At the stovepipe adapter and bottom section of pipe, can't that outer layer still be close to that 785 temp? I will put my magnetic thermometer on there to check, but I think these pipes should not be galvanized even with double wall.
I don't get as hot as I was now that I've cut the draft back... high fire levels around 450, low fire 150... did get up to 600 a couple times when the full draft was coming from the chimney.
Might look at replacing the pipe when I cut in the barometric damper.
Might look at replacing the pipe when I cut in the barometric damper.
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