Ventiliation help and tips, can I see yours? [Archive]

MikeAurelius

2005-09-21, 10:39am

Here is information on ventilation:

http://www.artglassforum.com/forums/showthread.php?t=1915

http://www.artglassforum.com/forums/showthread.php?t=1360

Basically, it's not the size of the fan that should control your selection, it's the size of the hood. You need to be at a minimum of 80 CFM per square foot of hood coverage.

Kitchen hoods, without substantial modification are not suitable for lampworking ventilation. They rarely have enough air flow, have odd sized ducting requirements, and can be difficult to modify. I'm not saying it can't be done, but you have to be ready to essentially gut the thing and start fresh.

Dale M.

2005-09-21, 10:52am

I would suggest you go right past kitchen vent type hoods and consider something more like the Glasscraft hood...

http://www.glasscraftinc.com/product/product_detail.cfm?part_id=1342

It does meet the minimum 100cfm "face velocity" that is acceptable for lampwork type hood.

As alternative I would suggest the concept of a industrial style fume hood or as some call it a "Barley Box"... Check out many good examples in STUDIO forum...

http://www.lampworketc.com/forums/forumdisplay.php?f=37

I specifically like this style hood in this thread...

http://www.lampworketc.com/forums/showpost.php?p=24182&postcount=6

But what every you consider, be sure it can achieve at least a minimum of 100cfm flow per square foot of face opening (this is a case where "more" might even be better).

Dale

Rhapsody Fire Beads

2005-09-21, 10:56am

So Dale, does that glasscraft hood have a built in fan? How strong is it? How close to my torch does it need to be? Is it better for Boro too?
~Suzy~

Rhapsody Fire Beads

2005-09-21, 10:59am

Thank you in advance Dale, for answering my question.
~Suzy~

SPIglass

2005-09-21, 11:25am

Hey Babs,

I got my range hood at Home Depot several years ago and it runs at 580 cfm and it was only $200. Here's a pic of mine right after my hubby installed it and a link to the manufacturer's website.

--Paulette

http://www.oshawa-bc.com/787.html

3919

Dale M.

2005-09-21, 3:46pm

So Dale, does that glasscraft hood have a built in fan? How strong is it? How close to my torch does it need to be? Is it better for Boro too?
~Suzy~

The Glasscraft system includes the hood, a 650cfm fan and 8 feet of flexible ducting (10 inch)...

For best working height, it should be as close to torch as you can get it, without bumping your head on it.

There is no real distinction about whether you work boro or soft glass. What you want be more concerned about is the processes, for instance fuming glass puts a lot more heavy metals and toxics into air stream than just basic glass work. Please understand though soft glass also releases heavy metals too, the are the basic colorants for glass.

Dale

Rhapsody Fire Beads

2005-09-21, 5:07pm

Thanks Dale! I am upgrading after getting loopey feeling while making a boro bead awhile back. It scares me!!!

~Suzy~

Bubbyanne

2005-09-21, 5:26pm

MikeAurelius

2005-09-22, 4:23am

Be sure you throw the flexible ducting away and replace it with smooth sided metal ducting. The flex ducting will reduce the efficiency of the vent hood by as much as 50%.

SPIglass

2005-09-22, 10:31am

Thanks for taking the time to answer my questions, the links and the pic. Lots of really great info and knowledge shared. This has been incredibly helpful!

Paulette, love your beads BTW, I have a lg. file saved of the beads you've posted in the S&T threads. =P~ Keep 'em coming! :biggrin: When are you going to make another fishy? It's been a while. ;)

Thanks so much Babs! I'm so honored!!! Yeah, it's been a while since I made a fishie...they just take me so freakin' long to make...almost 2 hours each. They are very draining and when people can't pay what they're worth....well, you know how that goes. Just too much energy spent on one piece as much as I love them. I did make a small one at GlassStock that only took about an hour. Loco (Bonnie) won that one during our fishie draw so "Sophie" went home with her. I did manage to get some pics of her before Loco took her home...

4020 4021

Bubbyanne

2005-09-22, 5:41pm

Aww Paulette,
She's beautiful. ...happy sigh....
Thanks for the eye candy.

Kaibeads

2005-09-22, 5:52pm

doesnt the size of the torch and flame have anything to do with the amount of exaust required? i cant see a small bead torch requiring as much as a larger torch for making marbles, sculptures or whatever... My range hood works great for my bead torch (lynx), if I turn the fan up too high it actually disrupts the torch flame because its sucking too much air and it's mounted several feet above the torch.

Dale M.

2005-09-22, 7:06pm

The current thought is to move a large quantity of air through hood, no matter what torch size is.... But Yes if you have huge torch, you should up the CFM's to a larger figure... I would not even go to the effort of building a hood/vent system with less that 100cfm of "face velocity" for even the smallest torch...If you are into huge torches you may want to consider a blower system that can supply up to 150cfm face velocity.

Flame disruption may not always be from fan/blower capacity, but from a turbulent air flow cause by "things" around torch that disturbs a smooth air flow ...

Dale

MikeAurelius

2005-09-23, 5:03am

Size of the torch "used" to be a criteria suggested by those who didn't know anything about ventilation.

To a certain extent, especially on smaller torches, even 100 CFM of so-called "face velocity" may be too much, especially considering turbulence issues as Dale mentions.

When using a bench mounted workstation hood, which means the sides and back extend all the way down to the benchtop, the "Recommended Practice" from the ACGIH calls for 80 CFM. This would be perfect for a small low velocity torch such as the Nortel Minor.

However, using a ceiling mounted or stand alone hood where the sides DO NOT extend down to the bench, 100 CFM of "face velocity" is not enough. You do need the 125 minimum CFM that the ACGIH recommends. The reason is that a higher mounted hood is pulling more air from the surrounding area than from directly in the area of the torch.

Issues such as this, making the distinction between hood types, is very important in deciding how much air needs to be moved. Simply applying a fixed number such as 100 CFM is just plain wrong. Ventilation is not a 'one size fits all' issue. Each installation is different and needs to be calculated on an individual basis.

Kaibeads

2005-09-25, 2:12pm

Cracked Baubble

2005-09-25, 2:57pm

here is my personal theory, if a range hood, even the cheapest ones, is intended to be used on a gas stove and oven.. 4 burners + oven, the oven is a big burner.. it will definitely work for ANY torch.. especially any bead torch. I've got a high end range hood which I'm sure moves more air than the base models. I'm sure the range hoods are tested thorougly and meet high standards as to how much they need to exaust from a gas stove.. like I say 4 burners plus oven.. WAY more than any bead torch.. anyway thats my theory. :)
the only problem I see with your theory is that the range hoods aren't designed to move heavy metal vapors.
GE doesn't expect that you'll be cooking with lead products or that you'll be using said burners for hours at a time (unless it's a resturant style hood, in which case it's probably great for torching since from what I've seen of those they move 600+CFM)
also, I don't believe that range hoods are designed to move much at all, in fact many don't even require any ducting and mearly act as a filter to remove the ash from the smoke when you burn dinner.

Yes I'm sure there are some range hoods that can do the job, those designed for industrial cooking, but in my search it seems that your average household range hood is a very poor excuse of ventilation.

Kaibeads

2005-09-26, 12:32am

Any hood over a gas stove would have to vent outside, and I would assume the burners kick out a lot of carbon monoxide.. more than a torch I'm guessing. I had an electric stove that had a hood that just blew right out of the top... no carbon monoxide or propane there.

Metals in the air from glass? yes, but they would get sucked out with the burning gases too... no hood is designed to move heavy metal vapors, they are all designed to move air. If the hood will suck out smoke, its gonna suck out fumes too.

MikeAurelius

2005-09-26, 4:30am

Uh, no. There are a ton of kitchen vent hoods that do not meet the minimum CFM requirements for the size of the hood. With lampworking, we are NOT dealing with household kitchen appliance ventilation. The torch is putting out NOX, not carbon monoxide. CO is NOT a major component of lampworking, NOX is, and NOX is not ventilated by low flow (CFM) ventilation.

This is a fairly common misperception of what is required for lampworking ventilation.

I invite you to read the following documents to help clear up some of these misconceptions:

http://www.artglassforum.com/forums/showthread.php?t=1915

http://www.artglassforum.com/forums/showthread.php?t=1918

Cracked Baubble

2005-09-26, 8:43am

Thanks Mike!

Kai, gas stoves in homes are not requiered to vent outside, well at least not in my county. In fact my gas stove hood is one of those worthless, ventless things. I doesn't really even do anything but push the smoke around.

Kaibeads

2005-09-26, 4:48pm

cooking with gas inside without ventilation.. interesting.. or uh, dangerous.

Kaibeads

2005-09-26, 4:48pm

Mike, I would have to register to read those posts, darn.

MikeAurelius

2005-09-27, 4:30am

Actually Kai, you shouldn't. The board is open to read for everyone.

edit to add -- Kai - try it again. There WAS a problem with the permissions and the links should work now.

Sorry about that!

Kaibeads

2005-09-27, 12:51pm

Oh cool Mike, Thanks for making the permissions so I could access the posts.

I read the posts, sort of. Mainly I was interested in the part two, doing the numbers post. I basically already know all the factors of good ventilation. Your post does an excellent job of breaking down the specifics. One thing I'd like to note is.. the ACGIH is for industrial purposes, and like you mentioned the closest comparison was resaraunt cooking. Which I assume they are using a lot more burner power than any common home cooking setup. I am also going to guess that a commercial restaraunt setup burns a lot more gases than a lampworking torch. Especially a bead torch, but even more than larger torches too. Then the post states that torch size is not calculated for because it's not really a factor? This, to me, seems a little absurd. What I get from this method of calculating ventilation requirements in relation to torching is that it's kinda like putting a dual exaust from a mustang on a scooter. Of course it's not quite the same but it sounds like overkill! For the common beadmaker this just sounds like way too much. For a teaching studio like yours, I think it's more appropriate. I remember seeing pics of your ventilation system for multiple stations and it is quite impressive... but man that is some serious overkill for one bead torch! Great work on your setup though! I think your information is completely valid, but its not a direct study for lampworking, it's adapted from commercial cooking requirements. That's the only thing that makes me suspicious.

Commercial cooking / Lampwork torch? Somehow the two just don't seem to compare.

MikeAurelius

2005-09-27, 1:08pm

As I noted, it is the closest application to what we do. The ACGIH can't of course come up with numbers for every single ventilation situation.

The 80 to 125 CFM per square foot range is considered to be average air movement. I discussed this very issue with my ventilation friends and also with a building inspector who specializes in mechanical engineering (which includes air movement). The issue is not the size of the torch, truly. Granted a large torch will put out more heat and more fumes than a small torch, but it is not the quantity or amount of fumes as it is the necessary air movement to get the fumes moving and up and out of the area. 80 CFM in an enclosed box such as the hoods I and other use is the minimum required. 125 CFM is the bare mimimum for a ceiling mounted hood.

The issue is one of creating a draw, and with low volume, low flow fans, you cannot create a draw. 80 CFM per square foot is not that much velocity - it is about 75 feet per minute (which is very low, considering that inside a duct, we usually like to see around 2000 to 2500 feet per minute).

My workstations are calculated based on the exact same principles: 80 CFM per square foot of "face area" (or opening) of the hood. The actual is slightly higher due to design issues in the ducting and the fan (you can never find the exact CFM requirement in a fan, so you should always go higher, never lower), but each workstation is designed for 80 CFM per square foot.

Kaibeads

2005-09-27, 10:24pm

Oh I see, so basically the velocity of the air is most likely calculated to allow for 0% of fumes to escape the exaust. But maybe lower velocity would allow 10% of fumes to escape and go around the hood. But after how much time would the escaping fumes actually reach measureable levels, I wonder. Possibly only after several hours? Anyway, why would lower volume vent hoods be created for oven ranges, if not because they are being used in smaller applications than commercial setups, I also wonder.

MikeAurelius

2005-09-28, 4:37am

Most kitchen hoods are slightly better than useless.

I won't comment on allowing certain percentages of fumes to "escape". The point of the ventilation is to ensure a safe working environment. The whole point is to remove ALL of the fumes and allow nothing to escape.

Do YOU want to take chances with your health or that of your family if you work in your house? I certainly would not make that decision for someone else. The best thing to do is follow the standards and recommended practices without questioning the basic reasoning.

Kaibeads

2005-09-28, 1:16pm

But my point is, the standards you are referencing, are much higher than a common lampwork beadmaker would require.

Dale M.

2005-09-28, 1:32pm

But my point is, the standards you are referencing, are much higher than a common lampwork beadier would require.

NO...... The standards we are recommending are the bare MINIMUM the lampworker should be using... If you are using anything less you are putting your self in danger either out of ignorance or indifference. I doubt you will find any informed source that will reccomend anything less that the specifications you will find posted here..

If you are in doubt check on ISGB forum or AGF or any other sites with informed glass workers.

I also challenge you to put up the specifications and the source(s) you are quoting!

Dale M.

MikeAurelius

2005-09-29, 5:52am

Kai, you have totally missed my point in my previous posts. The Recommended Practices put forth by the ACGIH may "refer" to commercial kitchen useage. As I pointed out, our useage is different and this is the closest to that usage. What I didn't say is that the commercial kitchen useage is also the lowest CFM rating of all the Recommended Practices.

Any mechanical engineer will tell you that you deviate from Recommended Practice at your own risk. These Recommended Practices are used as a standard by building inspectors and code writers.

Let's say for a moment that someone decides to ignore the Recommended Practice and uses 50 CFM per square foot of ventilation. After a few months of operating, members of the family start to experience headaches and other symptoms of NOX poisoning. Various medical exams ensue. Insurance pays for the exams but requests an inspection of the house. Inspection finds that there is not enough ventilation, that the ventilation is not to "code". Insurance is cancelled and all payments already made are reversed.

This is an example of what "MAY" happen.

Ventilation is nothing to be messed around with. The only suggestion I can give to you would be to follow the Recommended Practices. No one who knows ventilation is going to tell you any differently, and if someone DOES give you different information, with all due respect, they don't know a damn thing about ventilation.

I spent over two years working with an industrial fan manufacturer designing and writing software for their fan selector products. I know fans and ventilation inside out. I've also seen the bad side, where insufficient ventilation has caused serious problems and even deaths. Don't mess around with trying to do less than recommended. It isn't worth it.

Kaibeads

2005-09-29, 7:04am

But if my vent hood is .5 square feet, then 50 cfm is 100 per sq ft. Perfect!

MikeAurelius

2005-09-29, 7:48am

A half square foot is 72 square inches. That's 12" x 6".

That's NOT a hood. Something that small is not going to function at all. Sorry.

You need to trap the fumes in a given space and exhaust them up and out. This entails a hood that is usually in the neighborhood of 2 feet deep and 2 feet wide, at a very minimum. For a ceiling mounted hood, you are looking at 500 CFM.

Why are you so intent on moving so little air?

Kaibeads

2005-09-29, 11:51am

Mike, I'm not intent on movng so little air, I'm just trying to show you the loop holes I see in the 'standard' you are using. I didn't see anything that said there was a minimum hood size in your 'doing the number' post. And you said it was more about velocity in an earlier post. Also you said that someone can't actually figure the exact cfm requirement in a fan due to design factors in the hood and ducting. This is why I'm showing the variable factors of the hood and ducting. For instance on your own design, the hood is 'yay' big but the actual port for exaust is obviously not the entire size of your hood, I'm guessing. So differnt types of systems move air differently, but no one really knows what is adequate for moving exaust from a torch. What I'm getting back to I guess, is that each torch creates X amount of fumes and that is dependent on the size of the torch and how much fuel it burns. Also how much glass someone is melting at any one time. The size of the torch MUST be a factor in order to calculate what size hood is needed and how much velocity and volume of air moved? Why not build the standards to the actual application rather than adapt standards from something totally different. I know you are concerned about building codes and such but a hobby type lampworker should have reliable information that would be appropriate for their application.

MikeAurelius

2005-09-29, 12:15pm

Ok, let's step throught this.

First, there are no loopholes. If you follow my discussion through the planning stages, you will see that everything starts with a hood dimension. Hood dimensions are based on work area space. You cover the working area of your torch. As I pointed out above, this is typically an area of about 4 square feet. Some folks go smaller, most usually go larger.

And yes, given the availability of fans, you usually can not get a fan for the exact cfm you need, so, again, as I wrote, you go to the next highest cfm available. It doesn't matter that it's not exact, just that you are moving AT LEAST the minimum requirement.

No, the ducting is always smaller. The hood is large to trap the fumes, and the ducting is smaller to create draft and flow to keep the fumes moving at a high enough speed to exhaust them out of the system at the end. This is the way conventional exhaust systems are designed for commercial and industrial installations.

Every torch creates X fumes. X does not increase all that much by increasing the size of the flame. Truely. It doesn't. Remember, we are NOT talking about CO. CO is not the factor. Its NOX. NOX requires high draft, high volume air movement, plus a large enough hood area to trap and exhaust it. NOX doesn't have the high velocity that the exhaust plume has, it moves a lot slower.

The ACGIH will certainly NOT create a standard just for lampworkers. It won't happen, ever. We are way too small of a niche market. We don't even appear on their radar. What we do is use the existing standards and recommended practices, as written. This is standard practice used by building code officials across the country. When a given installation does not fit into a previously decided category, they look to see what it COULD fit into. I could have gone to several other classifications in the ACGIH, like fume hoods over chemical baths or dust removal hoods over grinding operations, but as you can see, they really *don't* fit the use.

As I said above, if you choose to NOT follow those standards and recommended practices, that is certainly your decision. But no one is going to help you figure out the wrong way to do it. I won't. Dale won't. Although Dale and I disagree on the lower limit of face velocity, we both will follow the standards and recommended practices.

We've both spent considerable time in the past couple of days discussing this, but I still don't understand why you fundamentally disagree with a standard that every mechanical engineer not only adheres to but is required to adhere to. It doesn't make sense to me. (Oh, and just so you know, there is another set of recommended practices out there which want to see even HIGHER CFM per square foot moved. I am being very conservative in my discussions just because we are using bench mounted torches and not a commercial kitchen stove.)

Kaibeads

2005-09-29, 1:19pm

Neat, thanks for stepping through it with me.

I guess I need to ask you what NOX is, I'm guessing hazardous gases produced from ingredients of molten glass. Wouldn't it make sence that a larger torch would be melting much larger masses of glass? Therefore creating much larger quantities of NOX, proportionately? I have a feeling there aren't any numbers for that factor. But if there are I'd be interested in learning about them.

MikeAurelius

2005-09-30, 4:31am

NOX is nitrous oxides. Here's a breakdown on them, the best I've seen:http://www.isgb.org/info/safety/nox.shtml

http://www.isgb.org/info/safety.shtml#29

Dale M.

2005-09-30, 7:33am

NOX is nitrous oxides. Here's a breakdown on them, the best I've seen:http://www.isgb.org/info/safety/nox.shtml

http://www.isgb.org/info/safety.shtml#29

Ahem... Mike, its NITROGEN oxide, not nitrous oxyde, think you did a typo....

Dale

MikeAurelius

2005-09-30, 8:43am

yep, my bad. Thinking about my dental appointment later today I guess ;)

Kaibeads

2005-09-30, 11:00am

Okay so I read those pages and a little more about nitrogen oxide. I guess it's a byproduct of combustion, which further leads me to believe that the amount of fumes is directly dependent on flame size, or technically the amount of fuel being burned. Imagine if the byproduct WAS nitrous oxide.. haha torching would be hilarious! Anyways thanks for enlightening me a bit on some specific ventilation factors! I think until extensive testing has been done with various sized torches and various ventilation designs it would be hard to determine what is really required.

I think it would be neat to get a project started that allows people to obtain supplies for testing NOx and other lampworking fumes, then their results can be compiled into a database with torch model, ventilation size and capacity, number of hours per session and any other related factors. Then once enough numbers are collected, tests can be performed to determine what factors can be changed to improve exaust systems for specific lampwork setups.

Dale M.

2005-09-30, 4:44pm

Kaibeads

2005-09-30, 6:01pm

Unfortunately the only way to get a precise data base on what gases and volume of gasses are spewed out in torch plume is to do the testing of all torches in a controlled laboratory experiment.

Just an accumulation of a lot of haphazard information from anything from the poorest designed to the most sophisticated hoods with anything from no instrumentation to the absolute best instrumentation is not going to make any database of definitive values for each hood and torch combination. All things considered here would be just infinite variables. Best solution is to adopt a industry standard that will assure that you have adequate ventilation. A simple test that is not always conclusive but reassuring is while torch is in operation and ventilation is running is to use a smoke test to be sure there is a positive air flow into hood and up the duct to blower and out exhaust. Though some don't agree, it is common to industry to use the smoke test to ensure the ventilation system is operating properly.

The gases and heavy metals spewed out in flame plume are toxic. They can kill brain cells. I don't know about you, but I don't want to sacrifice any of mine...

Dale

Any multiple number of tests would be better than none or one. I agree with the smoke test theory. But smoke and metal fumes arent really comparable.

For one person to create a controlled envoronment with numerous torches and hoods and invest the time to test all of them and combinations would be a great endeavour. But for numerous individuals to obtain supplies for testing the setup they already have and submit results to a common database would probably give a much broader spectrum of results and much larger sample of information. A simple procedure for how to perfrom the test would need to be outlined. The procedure could include, record certain variables, such as, torch, hood type, hood size, cfm, distance of hood from torch.. anything else that might be a variable factor. Then the supplies could be directed to be used in a systematic fashion, such as after so much time torching and at a certain distance from the torch. If enough people were able to participate I believe useful information could be obtained.

MikeAurelius

2005-10-01, 12:45pm

Mustang Dawn

2005-10-01, 4:37pm

Hi Dale and Mike,

I went to my friend (Pete) who owns commerical Ventilation shop (they make the vents & stuff for big buildings) He asked me what size I wanted and showed me the back room where they had some stuff hanging around. He had one that would be perfect. But I noticed on the bottom of it there were slats on the bottom of it, maybe 4 to five inches of metal and then one inch of opening. This was accross the bottom of the vent hood. I told Pete that is the size I would like but with out the slats on the bottom. Pete said that the slats increase the pull of the fan. He then took me out to the work shop and showed me some HUGE ones used for venting welding that had the same set up. So my question to you two is should I have him put the slats on the bottom or keep it open. He can make one that sits on the table too. He said just give him the dimentions and he'll make it for me :)

I hope I'm making sense. I plan to buy a 650 CFM fan.

Thanks, Dawn

Dale M.

2005-10-01, 5:09pm

Could the slats be a opening for makeup air? Or were they just "channels" for air flow around "work"?

Dale M.

Mustang Dawn

2005-10-01, 5:58pm

No these were not makeup air slots. They are the slots to vent out the air.

Dawn

Kaibeads

2005-10-01, 7:13pm

The only problem, Kai, is that for the data to be any good, everyone doing the testing must use the exact same test equipment set up exactly the same way every single time. Otherwise the data is worthless.

Thats why there would be a specific process for setting up the test with criteria like I mentioned. Therefore the data would actually be quite helpful if enough was gathered. The more info the more helpful, obviously.

Bubbyanne

2005-10-01, 10:04pm

I have some more questions. :grin:
We spent some money tonight and got a few things to put a system together. I need to know before we get started if we did okay with our purchases and if the design we have in mind will be sufficient.

We bought a 500cfm (Axial type) 8" In Line Duct fan. This will be reduced to 6" then again to 4" then vented out the window with one bend somewhere in there, possibly. It will be a very short run to the window and the fan unit will be located over my torch, connected to the hood, which my husband will construct out of sheet metal.

Will a 3ft by 2ft hood be sufficient for this fan? Bigger, smaller? The whole static pressure thing confuses the heck out of me too. Numbers make me go cross eyed so please just tell me will it be okay to use the reducers in this manner?

Oh I should also mention that my set up is in my large open basement. I have a big escape window I open when I'm working and there's no door to the upstairs so I don't believe make up air will be a problem.

I hope I said everything clearly enough to give you an idea of what we're thinking and I thank you for your help.

Kaibeads

2005-10-01, 10:54pm

reducing the duct size will greatly reduce the efficiency of your fan. a 3 x 2 foot hood would be about 80 cfm per square foot with a 500 cfm fan. the cfm of the fan would be reduced by the reduction of duct size the tha actual cfm of the hood would also be reduced.

I would recommend not reducing the duct size and that would probably be great!

Dale M.

2005-10-02, 9:11am

A 2ftx3ft hood will give you a "face opening" of 6 square feet. A 500cfm fan will give a "face velocity" of 83.3 cfm. If the inline fan has a specific duct size connector on it I would stay with that size duct. Reducing it down may increase "duct velocity" (speed of air through duct) of exhaust gasses, but may reduce the air flow if fan can't maintain enough pressure to move large quantity of air... I'd maybe reduce face opening a little and use at least 8 inch duct through out system, also keep ducts as short as possible and as few turns as possible.

Dale M.

MikeAurelius

2005-10-03, 4:45am

Babs, the diameter of the ducting should never be reduced. It significantly increases the static pressure (back pressure). With two reductions in size and a 90 degree bend, it is quite possible that the static pressure will be so great as to stop moving air, causing the fan to overheat and the motor to burn out.

Keep the duct at 8".

evenia

2005-10-05, 5:17pm

My DH & I have spent the last hour doing some research on the web about NOx. So essentially what we have found is that according to the article listed above -- http://www.isgb.org/info/safety/nox.shtml -- torches measures 15 parts per million of NOx. Articles discussing related combustion processes highlight that for example a gas stove emits 40 PPM per burner; and emmissions limits for natural gas water heaters suggests up to 80ppm are tolerable. 100 ppm was listed as a current health saftey standard and that california proposing that 30 ppm be considered "low NOx emissions". Texas is at 50 ppm. Once I move my studio into my smaller space I will still get Mikes blue prints and build a ventilation system but it looks like that torches might not be as bad as thought.
Here are the links where we found this so you guys can look at it if you want to. I hope this doesn't piss off anyone, I just wanted to learn more about what I have been breating for the past 2 years because I didn't realize I needed ventilation. Then I wanted to share the facts I found.
http://www.coen.com/i_html/white_costsaf.html
http://www.coen.com/i_html/deltanox.html
http://www.sparetheair.com/faq.cfm
http://www.awma.org/education/elearning/AIR311E.asp
http://www.cleaver-brooks.com/Emissions1.html

Kaibeads

2005-10-05, 7:12pm

Very interesting post evenia. Makes me more curious about widespread testing with lampwork setups.

evenia

2005-10-05, 7:14pm

I would like to see more test run on our type of torches we use to make sure that it is only 15 PPM of NOx. I have NO idea how to go about that though.

jokersdesign

2005-10-05, 7:32pm

I'm trying to get a hood made like this one. Do you think the angled roof top is better or if a flat top roof would be better?

http://www.glassartists.org/Gal708_clean_shop.asp

Kaibeads

2005-10-05, 11:49pm

I would like to see more test run on our type of torches we use to make sure that it is only 15 PPM of NOx. I have NO idea how to go about that though.

I was only able to find nitrogen oxide detector tubes. a 10 pack was around $50 - $60

I'm trying to get a hood made like this one. Do you think the angled roof top is better or if a flat top roof would be better?

I think angled hood would work well, might depend on the exaust duct size and shape.

MikeAurelius

2005-10-06, 4:35am

Ok -- first of all the standards shown DO NOT show the acceptable standards for sitting 8" from the flame. This is what you have with a glassworking torch. The NOX standards should be much tighter for lampworking because of this. You are sitting 8" from the flame for hours at a time. Even considering a gas stove/oven, you spend only short times in front of the stove/oven.

Don't dismiss the importance of removing NOX on the basis of non-related "appliances".

Robert - a flat top on the hood is going to be easier to build and easier to duct out. Being angled makes absolutely NO DIFFERENCE if there is enough exhaust CFM to pull the fumes and heat.