Vent Fan
Linda Nicholson -- Monday, 22 October 2001, at 4:24 p.m.

At long last, (it's been a year and a half since I had my last studio), I'm setting up my equipment in a friend's garage. My only option for exhaust ventilation is to remove an 8"x10" pane of glass from a window and install a fan there. I think I can make a suitable set-up using 8" ducting and an axial fan (6-15/16" x 6-15/16") which I found through Grainger.com. Part #5C157. It moves 340 cfm and should be nice and quiet. Cost is $85.05. I plan to mount the fan close to the window, with the distance from the fan to my torch being about 6'. Will the six foot distance significantly reduce the drawing power of the fan? Is 340 cfm adequate for this application? What do you all think? Does this sound like a pretty good system? I've read previous posts and didn't see any information specific to axial fans which I'm choosing because of it's purported quietness. Any input is greatly appreciated. I hope to start buying the components tomorrow. Thanks all. Linda (*Sideways* with excitement!!) Yes, Theresa, it's true. Send me good thoughts. Grin.

Vince Henley -- Monday, 22 October 2001, at 5:31 p.m.

Linda,

the 340 CFM might be adequate, but it depends on some other variables. Will the duct be between the fan and whatever collects your fumes? Or is the fan just in the window? Is the fan in the duct or is the duct mated to the fan via a transition section? I'm trying to assess the coupling between the fan and the fume collector and whether the fan pushes or pulls the air though the duct.

What is the source of your make-up air and how is it positioned relative to your workstation at the torch?

If you thought of your torch as a hose nozzle, where would it squirt relative to the fan or collecting device for the fumes? What torch are you using?

Axial fans are great and can be very quiet. No problems with your choice in that regard. As I remember, Grainger has quite a few suitable axial fans for this application, including several "in duct" types.

You can email me off the forum if you want to discuss this in detail.

Vince

Carol Holaday -- Monday, 22 October 2001, at 6:15 p.m.

Linda and Vince,

I hope you will keep your discussion re: exhaust fan/system on the forum. I am sure there are many, myself included, who are interested in this topic and would like to read all the facinating details.

Vince - despite all of your great help when I posted questions re: exhaust system design, I am STILL without! I printed out your advice and information, made lots of notes and drawings, did much other research, and then called a heating and sheet metal person to put it together for me. $3000.00! Way out of my budget. This is not a money making venture, more of a play time thing. Naturally I want to protect my health, but I am sure it can be done for far less. Next guy that came and looked at what I have in mind came up with more problems then solutions. He is researching used equipment and will get back to me.... but I am thinking that this is not the person I want to deal with. Wednesday I have an appointment with yet another heating/plumbing/sheet metal person, and am hoping this is the one that will get it done. Meanwhile I am doing non torch jewelry making and my bead making skills are not progressing. What a saga! Carol in Monterey

Vince Henley -- Monday, 22 October 2001, at 6:53 p.m.

Carol,

I am certain, unless you are doing something exotic, that you can put together an adequate ventilation system for a single bead making work station, for much less than $500. My current test ventilation system on which I am doing the study measurements, cost less than $150. So far, all the measurements indicate that this is an adequate solution for a single station, Minor class burner, workstation.

Do you happen to live in a "high rent" district where the local costs are commensurate with the economic status of the community? Do you have some unusual construction problem that also must be dealt with? Are you attempting to make a laboratory-grade installation? Is this a "built-in" highly finished furniture grade installation? If any of these are so, I can understand the high estimate. Otherwise, a half hour trip to Home Depot with a skinny checkbook can solve this problem, assuming you or a relative or a friend are reasonably adept with basic everyday tools.

Vince

Carol Holaday -- Monday, 22 October 2001, at 8:02 p.m.

Vince,
Nothing exotic (at least not to my thinking), although it will go well beyond the range hood idea. No windows in the garage will mean a hole in the wall for the exhaust duct. A pyramid or funnel shape hood directly over the flame throw area, a quiet fan 6' away from the hood, sheet metal for the table, sheet metal to protect the drywall, plumbing to outdoor tanks... that is about it. I am thinking maybe close to $1200. I am fairly adept with tools, but draw the line at cutting a hole in the house, plumbing gas lines and bending sheet metal. Yes, I guess Monterey is a high rent area, so I don't expect any big bargain, just something within reason. I will continue to shop around until I find something I feel I can afford that will be right for the task (pulling fumes out of the work area). As usual, my Virgo nature is obsessed with "getting it perfect". Maybe I'd better let go of some of that if I want to get it done this year.

Grainger's first recommendation to me was a 325 cfm in-line fan placed at the wall with a 6' long 6" duct to a small hood over an area with enclosed back and sides. That seemed a bit weak for the design (I am thinking more of a 8" duct and a 500 cfm variable speed fan), but maybe not if the face of the hood is about 16 to 18" across and down low near the flame.

What does the hood of your test ventilation system look like? Where is it in relation to the flame? Did you share your test results on the forum already?

Once again, thanks for all the information. Carol

Zillatron -- Monday, 22 October 2001, at 9:39 p.m.

here's a link with some info about venting http://www.lni.wa.gov/wisha/p-ts/Ven...ault.htm#Hoods

Emmett's Glass

Vince Henley -- Monday, 22 October 2001, at 11:30 p.m.

Carol,

well, you ARE talking about a lot more than just a vent fan. What you just described was all the mechanical construction for a studio, not just the ventilation system. Frankly, given the option you described, I'd say that the 500 CFM fan is a better choice, with at least an 8 inch duct. Part of the equation will be the size of the hood and the air face velocity at the hood opening. 500 CFM is about minimum for five square feet of hood opening, or about 24 X 30 inches. If it is larger then you should have more CFM.

Possibly, if I might suggest it, you could have a significantly more modest investment, get on with making beads, and improve the system over time.

I have not yet posted the hood measurement results. But basically it is a standard consumer range hood in stainless steel. The hood opening is nominally 18 inches by 30 inches and the axial, very quiet, fan is rated at 220 CFM with a 7 inch round duct. However, my measurements show that the fan actually averages 307 CFM with an in-duct velocity of 1060 FPM. The air velocity measurements are done with an NIST traceable calibrated thermoanemometer. The lower lip of the hood is 28.5 inches above the bench datum. A rear baffle extends 9 inches below the lip of the hood and 9 inches beyond each side edge. Side baffles the same length are being evaluated. The torch barrel extends 2 inches beyond the front datum of the hood lip. Make-up air source is greater than the fan capacity and is sourced from directly behind the workstation and begins six inches above the floor. All joints in the 7 inch round duct are mechanically fastened with screws and then taped and the duct is vented through a turbine roof vent directly above the hood. The total duct run is about 13 vertical feet with two shallow bends near the exhaust end. All openings in the hood that are not directly connected to the duct are sealed with tape. The filter screen has been completely removed and results in a 14 percent increase in airflow. With the filter removed, the face velocity is a nominal 82 FPM, but that varies greatly across the face. The hood is manufactured by NuTone, model number WA6530SS, and is commonly available at Home Depot and other outlets for costs of around $100.00 - $125.00. The stainless steel version is the most expensive, painted versions of the same hood are cheaper.

In the current setup, there are various instrumentation ports and structures around the hood, but it can be, and has been, used to actually make beads, including operations requiring heavy fuming. There has been no measured evidence that any fumes from beadmaking escape the capture zone of the hood. This would not be true without the baffles, so the bafffles are an essential part of this system.

That's about the most I'm prepared to say at the moment other than that the measurements are tedious, numerous and time consuming.

Vince

Lezlie -- Tuesday, 23 October 2001, at 7:03 a.m.

Hi Linda,
I got the Nutone Hood vent (like Vince mentioned) from Home Depot, along with the handy dandy ductwork, some hooks, chain, and a roll of duct tape, and installed that puppy myself, vented through a window pane. Took a few hours to install,and I found that my vocabulary was greatly expanded during the installation! LOL! I'm not particularly handy or patient when it comes to things like this, and I definitely had to put my Virgo perfectionist tendencies away for this one since the installation isn't exactly a thing of beauty, but it fit into my budget, and I really love it! Works like a charm and is really quiet (spring for the top of the line as it makes a difference in the noise) In addition to all that I love the lights it has. Those weren't even a consideration when I bought it, but the low light setting is just perfect for lampworking! I find I don't pick up the wrong color rod half as often now I can see them better.
Just to be reassured that I'm not doing damage to my lungs while I'm working makes it a thing of beauty in my eyes, and best of all I did it all myself!

Edward Q. Smythe -- Tuesday, 23 October 2001, at 8:09 a.m.

Vince, were you able to measure the static pressure at the time of your tests?

I've been looking at a couple of options ranging from a "traditional" exhaust fan that run between 845 CFM at 0 SP to 315 CFM at .25" SP, to a vent hood style like you discuss above.

I plan on building a table with a 3 side enclosure plus top, and have the hood or ducting mounted so that there is a slit vent to draw the fumes and heat from the enclosure.

Carol Holaday -- Tuesday, 23 October 2001, at 10:02 a.m.

Vince, thanks for the details. "Datum"? I may not be improving my beadmaking skills at the moment, but I am certainly increasing my vocabulary and knowledge of ventilation issues!

I have printed out your description of the system you are testing and will make a drawing of it to help me visualize and discuss it with the next fellow that might put it together for me. I expect that the duct being vented through the turbine roof vent directly above the hood greatly effects how all of this works, as does the perfect location for the make-up air source. Wish I had these options. The other measurements you listed are very useful and will help me decide on the optimal size and location of the hood.

I will phone Orchard Hardware this morning and see if they have the NuTone model you are using for your tests. I'd like to have a look at it. You are right about just getting something done so I can get to work, and improving later as needed. After all, I am not fuming metals now, or working with boro (yet). Thanks for sharing the test results, etc..

E.Q.S - about the slit vent design.. Not sure how that differs from a slot hood design with side baffles (like we have in our jewelry lab where I teach). I like that the fumes are pulled back and up instead of simply up from the soldering area. Actually the system is too efficient! Sucks the flame out when we are using a small flame. Works fine for big flames. I don't know the size of the fan, but sure wish we had a reostat on it. This is an expensive design to build, not really an option for me right now, so I am attempting to come up with the best of all designs that fits my needs and wallet. I'd like to hear more about what you finally build and how it works.


Edward Q. Smythe -- Tuesday, 23 October 2001, at 11:04 a.m.

Carol - essentially the same thing...I'm way ahead of you on the rheostat - I have found one at Graingers, they have them in 3, 6, and 10 amp versions. "Permit adjustment between 50 and 100%." The cost from $18.37 to $44.97 each. 4YC44 4YC45 4YC46 (page 3714 catalog 392).

My main concern is two fold - first, not to just have this open hole where the fan sucks everything up into its maw. By using a slit or slot at the top back of the hood assembly, this will direct the fumes up and away, as well as drawing air across the entire width of the hood. This also acts as a flow restrictor as well - you get better fan performance from a smaller draw area than from an unencumbered hole in the wall.

Second, available room (house) combustion air. My future studio will be in the basement (gas and O2 piped in from the garage). The house is TIGHT - very few air leaks, and all my appliances are either supplied with combustion air, or have a source nearby. Once I fire up the torch and turn on the fan, a source of air needs to be available for makeup air (to use a HVAC term). When they plumbed my Jenn-Aire cooktop, the HVAC guy was quite displeased - they calculated that to properly provide combustion and makeup air for this unit, I needed a fresh air intake 18" in diameter, which of course was not feasible. So what we do instead (I can see Vince shuddering) is open a window in the kitchen when we fire up the grill.

The other thing you have to think about is the amount of air actually in your house. A 900 square foot floor (say the basement) has approximately 7,200 cubic feet of air in it. With a 300 CFM fan, you are changing the air every 24 minutes(much faster near the fan of course). In the dead of winter, you will need a heat source to keep the basement warm with that kind of exchange rate. Fortunately, my basement has hydronic in-floor heat, so I have a huge mass that is already at 68 degrees - I just have to watch the air temperature.

Vince Henley -- Tuesday, 23 October 2001, at 12:45 p.m.

I did not yet measure static pressure, but it is quite low, virtually zero. Basically the vent is unrestricted.

Vince

Vince Henley -- Tuesday, 23 October 2001, at 1:02 p.m.

Carol,

I don't think OSH has the range hood but Home Depot does. I am sure there is a Home Depot somewhere in the Monterey-Salinas area. I'm nearly local. The roof turbine vent was just conveniently placed for venting the test set-up, and has no effect of the exhaust. It is much larger than the vent duct and I actually had to build an adapter to seal off the roof vent so that all the vent exhaust would exit through the turbine. This test setup is not in my studio, which has been dismantled for relocation, but in my garage where it shares space with wood and metal working equipment. It's quite a mess at the moment, but sufficient for the study and to make the occasional bead. The whole affair is propped up on temporary supports for the work surface and the vent is hung from the rafters using square aluminum tubing to precisely locate the front of the vent and chain support for the rear of the vent so that it could be made level. It really is an experimental study mock-up.

Location of make-up air is very important no matter what vent option you choose. It would be beneficial to even add ductwork to position the make-up air source properly if possible.

For slit vent design, you will need a more powerful blower and more CFM than with a central overhead hood.

Vince

Carol Holaday -- Tuesday, 23 October 2001, at 1:17 p.m.

EQS - Since you specified the rheostat options, I wonder if you have a fan picked out? Are you building the slot hood or having it built or buying one ready made (big bucks I think)?

My studio is in a single car garage with a high ceiling, is attached to the house and under the living room. One door to outside, one door into house. No windows. The floor is always cold, but being on the California coast, it is never freezing cold (no matter what Mark Twain said about it).

Since I am planning for "local ventilation" and not "dilution ventilation" I am most concerned with what happens right in front of the slot area. I feel that with all the excellent input, and the links to more information offered on this forum, I am getting very close to getting this project done! Tomorrow's meeting with a ventilation/sheet metal/plumber guy will be my third attempt. Sure hope we can communicate and that he isn't put off by the 12 pages of notes and drawings I have, and the options I am concidering. Times like this I miss my father more than ever. He could build anything, fix anything, and loved to be of help.

I appreciate your input. Thanks.

Edward Q. Smythe -- Tuesday, 23 October 2001, at 2:01 p.m.

Carol - I haven't picked the fan (yet). I found the rheostats merely by chance while looking up fans for Heidi (she is in the same pickle as you).

My design is going to be built by my local HVAC to my specifications. The quote I got was $175 for labor and materials, this is a sheet metal enclosure 4 feet wide, 2 feet deep and 3 feet high. They are essentially going to make a modified plenum (the big duct that fits on top of your furnace). I got the idea for this design from a laminar flow booth I once saw. The only modification to that design was to move the air flow from directly in front of the operator to a slot/slit above the operator and at the back of the booth.

Of course, I have to haul it home, but this was well within the parameters that almost any HVAC company can bend on a press break. I could have gone larger, but that would have entailed some re-engineering to handle the additional weight of the structure.

The only thing I have not spec'ed yet is the fan...hence the interest in this thread.

Linda Nicholson -- Wednesday, 24 October 2001, at 1:28 p.m.

So many good responses - thank you all.

Vince - The fan will be mounted at the window with about 6' of ducting between it and the fume collector. I thought it more efficient to to pull, rather than push air from the room. It is an "in duct" model, I believe.

Unfortunately, makeup air is less than ideal and I have very little control over it. The building is large, drafty, and has a set of garage doors that can be opened to help the non-specific free flow of air, but, those doors are around the corner and down the hall, so to speak. That will be my only recourse for makeup air. I can't punch holes in a building that's not mine. This situation is, I hope, temporary.

I'm anxious to get behind my torch, (a Lynx), so am going to forge ahead anyway and want to make the safest use of what I have to work with. I do have a fitted, fume grade respirator with screw on canisters from my old welding days that I can probably talk myself into using. Urgh.

As far as torch tip in relation to collection device, that is still up in the air. I have a head full of design ideas, and feel confident that I can construct an effective setup using the parameters you outlined and from the site Zillatron posted. In my situation, do you think the range hood, with baffles, is adequate? If so, it would be, hands down, the quickest and easiest solution. There will still need to be 6' of ducting from hood to window. Thanks so much for your input Vince. We all appreciate it.


Vince Henley -- Wednesday, 24 October 2001, at 4:16 p.m.

Linda,

some range hoods can be a quiet alternative to a custom installation for a single Minor-class burner workstation. Mind you, these are not optimum, but they are adequate, and inexpensive. The duct length you mention is no problem, so long as it is a minimum size consistent with the airflow, in the case of a range hood, seven inch diameter round duct is standard, and adequate. The range hood I mentioned in the previous post has a Torrington Research axial blower that has shrouded blades and is very quiet. Baffles are required, but easily attached.

There are many possible solutions to any ventilation problem, but my interest in the range hood solution is an attempt to evaluate a readily available alternative that could be used by many bead makers who might otherwise have poor ventilation and increased risk. If we can develop good data on one or more of these, then we will better understand their limitations and can recommend some installation characteristics.

Vince

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Ventilation, Fumes, Misconceptions
Stan Wolfersberger -- Saturday, 13 January 2001, at 10:31 a.m.

Hi beaders,

Found a very nice, user-friendly site while meandering for other info at work. This will give those who want to know more about the "nuts and bolts" of ventilation an idea of terms, types of ventilation, and so on.

http://www.lni.wa.gov/wisha/p-ts/Ven...on/default.htm

Also, a few observations on postings that I have seen and some possible misconceptions.

Carbon monoxide - I have seen numerous instances where people have carbon monoxide (CO) detectors, and they infer that since the detector is not going off, their ventilation is adequate. Wrong!! If you use any type of torch with fuel/oxygen, it is very likely you will avoid the incomplete combustion that leads to elevated levels of CO formation. Also, the levels of CO that will set off your detector are usually pretty high, in the hundreds of parts per million (ppm). Note I am NOT saying that no CO is produced, I have previously related that I found low levels in my measurements, as did NIOSH. Your torch attains temperatures that are high enough to produce significant amounts of nitrogen oxides, NOx. Nitrogen dioxide is a severe respiratory irritant, and causes problems at much lower levels (concentrations) than does CO. See my earlier posts or articles for the Bead Release on NOx. Knowing which emissions are the critical ones to control is key to having an adequate ventilation set-up.

Set-up and Orientation of Hoods - There have been lots of folks who have described or sent in pictures of their equipment used for ventilation. Glad to see people are taking this seriously enough to invest in their safety! Note a few things that can improve your ventilation. It is much harder to "pull" air than to "push" it. The proximity of your hood to your torch can have a big impact on how efficient it is in ventilating the fumes. If you still notice odors, irritation, etc. it may mean your hood should be closer to the torch. Or, you can improve the effective pick-up of the hood by installing flanges. For example, if you look at the typical hood used over kitchen stoves as used by some beaders, this looks very much like a "canopy hood" when floated above a beader's torch. By installing side panels and a rear panel on this hood, you can reduce the impact of cross drafts. Also note that your torch itself gives considerable direction and velocity to the fumes you are trying to control. Thus, when testing your set-up with smoke, I always recommend doing this both with the torch off and on. Being careful not to burn yourself, of course. But this can often uncover a set-up where the torch literally "throws" the fumes at such a rate or angle that the hood is ineffective in capturing them.

How much is enough ventilation? - In plenty of my posts, and those of folks like Vince, Dave, and others, it has been noted that the quality is as important as the quantity. You must introduce fresh air to replace the exhausted air with fumes. If you live in a cold climate like me, yep, you have to open a well-placed window or door so that clean air can replenish what your hood or fan removes. I also am trying to approach this from a "first principles" viewpoint: Are there reliable information sources about the amount of pollution produced by each torch type? Based on this amount of pollution, and the specific hazards of each pollutant, how much ventilation is therefore needed? This should in principle guide how much face velocity (in feet per minute) is needed, therefore how many cubic feet per minute, etc. which would in turn tell you the types of fans and their size that would do the trick. So far, finding the info on torch emissions has been harder than I thought. But I am still looking. If anyone knows reliable sources for this kind of data, please write me directly.


Stan Wolfersberger

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Ventilation
Barbara Simon -- Monday, 30 October 2000, at 8:29 a.m.

Hey, Stan the Man! or anybody with knowlege: I am in the exciting position of being able to build a studio from scratch. What do I tell the duct guys or who ever (as a matter of fact, who do I call on to create a REAL ventilation system??) what to do? I can't believe this is going to cost an arm and a leg however I can Imagine a scenario where some really ignorant contractor is going to assert that it will cost me a fortune to have the kind of system I need. For example some kind of industrial over kill. Can any body give me input on this? So I am armed with knowlege........


Re: Ventilation
Dave Bross -- Monday, 30 October 2000, at 11:03 p.m.

Hi Barbara,

How about checking with suppliers of used or new restaurant equipment? Plenty of big ventilation stuff there usually. As far as installation you're probably going to have to shop the sheet metal contractors.

Dave

Re: Ventilation
Vince Henley -- Tuesday, 31 October 2000, at 12:40 p.m.

Barbara,

there is a new International Building Code that is making its way through the various jurisdictions. It is a consolidation of the two major building codes used in the United States with some new additions and is supposed to resolve some differences between the codes. Building codes are generally implemented by a law at the state legislature level, based on a model code, but each jurisdiction may impose standards more stringent. The states themselves nearly always modify the base code to suit their preferences and local conditions. Examples are earthquakes in California and hurricanes in Florida, each requiring modifications to the model code.

Check with your local building and planning department where your new studio is located. That will likely be your local town, city or county government, depending on where you will be located. They can tell you what code model is in use there, what year version, and whether or not there are state and local modifications to it. For planning purposes your local library may have code books you can reference, as may your local planning and building department. I do not recommend buying your own code books unless you have use for them as they are quite expensive and change often. The Building Code, the Mechanical Code, the Electrical Code and the Plumbing Code have sections relevant to your new studio. The building code deals with structures, the mechanical code with such things as ventilation and hoods, the plumbing code with such things as gas piping, and the electrical code with wiring. All will affect your new building. DO NOT ASSUME YOUR CONTRACTOR WILL ALWAYS DO THE RIGHT THING. Hire someone for an independent oversight such as an architect, or become familiar with the requirements yourself.

The opportunity to create a new studio is a wonderful thing, and it would be a good idea to implement everything with safety and code conformance in mind from the start.

If you need references to the code writing organizations, I can help you with that, but try your local Building and Planning department first. Very often they have summaries of their requirements for free, phrased in language easier to understand than the building codes.

Having said all that, any competent HVAC contractor, especially one who does industrial work (I know you don't like the sound of that, but that's what you want) can help you out. Someone who only does residential work is not likely to be familiar with the requirements for flame-worked glass and could easily create a sub-standard installation.

Vince

Re: Ventilation
Stan Wolfersberger -- Thursday, 2 November 2000, at 7:11 p.m.

Barbara,

Yes, that is a great position to be in. Most of what you need can be found in one book: The ACGIH book, INDUSTRIAL VENTILATION. (ACGIH = American Council of Governmental Industrial Hygienists). This book has all the design info one needs to construct (serious) ventilation for most processes. The only hitch for beadmaking, there isn't much (if any?) good data on the emissions from the various style torches. You could probably rely on the ventilation needed for various analytical instruments, like flame atomic absorption spectrometers, inductively coupled plasma spectrometers, or see if the Scientific glassblowers have a guideline.

Most of the advice I give assumes beaders are going to buy glass before they buy $1000 worth of ventilation. You can have good ventilation very inexpensively, but you do have to do more work (put the fan in the window, haul it out when you're done if it's cold, etc.). For a serious studio, I think excellent ventilation is the best investment you can make. But I just wanted the beginners to know that they can get by for very little, but they can't skip this most critical safety step.

Barb, I'd be glad to offer more specific advice if you write me directly. Also, my engineer buddies may know someone near you that you could call with confidence. Hope you have the dream studio of a lifetime!!!......Stan

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More Questions on Ventilation
Kelly Elliott -- Thursday, 16 November 2000, at 1:23 a.m.

Hi,
I'm having a weird problem ... I have an exhaust fan right over my work area. I'm running a propane heater maybe the first half-hour of my session, and turn it on here and there if it gets too chilly in my garage. Now here's the problem: I'm working on a hothead in my garage. After about 45 minutes, my nose starts to run. After two hours, my eyes are tearing so bad the tears run down my face and I have to call it a night! The fumes almost smell like Tilex does. Has anyone had this happen before? I'm on a new tank of gas - Propylene this time around - and didn't notice this with MAPP.

Just curious ...
Thanks,
Kelly

RedHot Beads

Re: More Questions on Ventilation
Vince Henley -- Thursday, 16 November 2000, at 1:38 p.m.

Hi Kelly,

my guess (for what it is worth) is that you do not have the ventilation you think you do. The fact that you have an exhaust fan is not necessarily the determining factor. If you do not have a source of "make-up" air equal to or greater than the capacity of the fan, you are just getting noise, not ventilation. Also, the relative positions of the make-up air source and the source of pollution are important. The fan could be exhausting relatively clean air and the stagnant air may be pooling near your work area. There are a number of scenarios. The fact that you seem to be getting a build-up of fumes, and possibly carbon monoxide, over a relatively short period would support this theory. You really need to analyze the flow of air from whatever make-up source you have, across your work area and through the exhaust fan to understand whether or not you have effective ventilation. There are instruments you can use to do this, but they are not common household items. If you know a friendly HVAC (Heating, Ventilation and Air Conditioning) person, they may be able to assist you with instruments that are common in that profession. There are other ways of doing this, but too long to explain in one of these posts.

Vince

Re: More Questions on Ventilation
Ralph M -- Thursday, 16 November 2000, at 2:50 p.m.

One of the cheapest, most readily available tools for checking your direction of airflow is a lit stick of incense. Of course, a cheap cigar will work, too....
(It won't give you any numbers about volume of flow. But if the smoke goes up, instead of sideways, though, that would be a clue.)

Re: More Questions on Ventilation
Vince Henley <Vince_Henley@gilroy.com> -- Thursday, 16 November 2000, at 4:15 p.m.

Indeed, smoke is one of the "other" ways I alluded to in my post. It will give you a quite good indication of directional flow and could be your first step to solving the problem. You could try it first and then decide what other steps might be needed.

Vince

Re: More Questions on Ventilation
Nancy Lawler -- Thursday, 16 November 2000, at 4:28 p.m.

You probably already know this, but it would be a good (great) idea to plug in a carbon monoxide detector near where you work. Don't put it up high because (I'm told) carbon monoxide is heavier than oxygen and tends to sink. So you'd want your detector somewhere around the normal household outlet level. Some people think they should be up in the air somewhere. At ~$30, a CO detector is cheaper than an emergency room visit ;-)


Re: More Questions on Ventilation
Sean Ellwood -- Thursday, 16 November 2000, at 4:30 p.m.

When I was first working in my house with just a window open this is exactly what happened to me. When I hooked up a 2 part fan that both pushed air into the room and then exhausted it the symptoms just went away.

What you are feeling is probably some kind of gas poisoning and definetly dangerous. Pop open a door or a windows and put in a big box fan pointed directly at you and see if it changes it at all.. If it does they you have just proven that it is a lack of ventilation.

thanks and stay alive ok? Don't kill yourself with the torch.
Sean Ellwood

Re: More Questions on Ventilation
Stan Wolfersberger -- Thursday, 16 November 2000, at 5:53 p.m.

Couple of points on this one: The situation you describe is WORSE than the situation of just a torch, as you have another combustion device (the propane heater) in your area. Thus, you almost certainly need MORE ventilation than the average beader. If you can, use an alternate heater (electric). In my wife's studio, the kiln provides more than ample heat, we don't need any kind of heater at all!

Also: Carbon monoxide is NOT heavier than air, it should not be mounted low near the floor. Follow the manufacturer's guidelines for the best place to mount. And carbon monoxide is probably not your greatest hazard, it is more likely NOx from the torch (and in your case, probably the propane heater as well). Nitrogen dioxide, one of the components of NOx, is a severe respiratory irritant. It will affect you at much lower concentrations in air than carbon monoxide. Also, carbon monoxide sensors are not set to go off at very low levels, so NEVER assume that just because you have a carbon monoxide sensor and it doesn't go off, you are Ok as far as ventilation.

Refer to my articles in earlier Bead Release issues for more guidance on ventilation do's and don'ts........Stan

Re: More Questions on Ventilation
Kelly Elliott -- Friday, 17 November 2000, at 10:36 a.m.

Thanks, everyone, for the guidance in this. I'm going to reconfigure my work area so I can get some air exchange through there. It's sort of hard with it being November in Michigan (and the worst of the winter yet to come), but we'll get it figured out one way or another! Last night I opened the back door of my garage a bit and that made a sizeable difference. Now I just have to get the air moving the right way!
Thanks again,
Kelly

Re: More Questions on Ventilation
cathy eggleston

try sticking a fan in the doorway facing out. It will suck the air outside. It worked for me. Cathy

Re: More Questions on Ventilation
Rita -- Friday, 17 November 2000, at 11:04 a.m.

Kelly,

If your glass rods start cracking and exploding remember that it is due to the cold temperature, especially if you have a door or window open in Michigan. When it gets cold or rainy here I have to warm my rods in the flame extra slow so they don't crack all the way up. Good luck and happy breathing

Re: More Questions on Ventilation
Nancy -- Friday, 17 November 2000, at 2:51 p.m.

I read in the literature that accompanied my CO2 monitor that they aren't reliable in the garage -- I can't recall the reason, but I think it had something to do with draftiness. You might want to check your literature for that if you still have it. Of course, I still have mine set up in my garage -- but it did go off one day while no one was out there and everything appeared to be fine. That hasn't happened again.

I work in my garage and while Seattle winters aren't anywhere like Michigan's (as I recall, winter was one reason for moving here from Ohio) it's still cold. I moved my kiln to the top of my workbench for added warmth and have a small space heater but putting the heat on my legs really helps.

One thing I've noticed is that my bead release is pretty persnickety now and I think it may be because its cold and damp out there now -- so I'm keeping my mandrels in the house until I need them -- it helps somewhat.

***************

Range Hood Ventilators
Vince Henley -- Tuesday, 27 March 2001, at 4:58 p.m.

I've noticed that some bead makers have pressed the common kitchen range exhaust hood into service as a ventilator for their bead-making bench. This is a relatively low cost solution that may work for many installations, but I've never seen any real information or measurements on it. So, I thought I would investigate and measure such a set up and publish the results here as a service to my fellow artists. The investigation has started but the final results will need to wait until some time after I pay the official government sanctioned bandits on April 15th.

In the interim, for those of you using such exhaust hoods, here are a few suggestions to improve their effectiveness. Later I will have numbers to go with these. This assumes a standard 30 inch range hood with an exhaust fan with a specified capacity on the order of 200 CFM. When I publish the numerical measurements I will provide the complete physical paramenters of the test setup.

1. If your hood has a filter over the fan inlet, remove it permanently. This application is not trying to catch grease and the filter reduces the airflow significantly, even when new.

2. Ensure that all duct joints are taped with duct tape. Also, tape or seal the duct adapter where it joins the hood, usually as a flat plate or flange fastened to the hood with sheet metal screws. Leakage of exhaust products can be significant with untaped joints in a pressurized duct.

3. If the upper or side surfaces of the hood have any holes used for mounting or unused cut-outs, tape them as well to ensure that all the air trapped by the hood has a chance to be captured by the fan and not flow out into the room.

4. If your hood is one that has an option to exhaust air back into the room, normally blocked off by a plastic or metal insert in outside vented installations, use duct tape or sealant over or around that insert to eliminate pressurized air leakage back into the room. If you can feel any airflow from the recirculating vent, it isn't sealed.

5. If your hood is suspended over your workstation and not flush against a wall, install a metal baffle as wide as or wider than the hood, attached to the rear vertical surface of the hood, and that projects down ten or more inches below the bottom edge of the back surface of the hood. This baffle keeps high velocity combustion products from the torch from flowing past the hood before the fan can capture them. The resulting low velocity eddy under the hood is more easily captured by the fan and exhausted from your work area. Light gauge galvanized or aluminum sheet metal works well for this baffle.

Vince

Re: Range Hood Ventilators
patti -- Tuesday, 27 March 2001, at 5:07 p.m.

Thank you Vince. I am in the pre-process of setting up my garage as a workspace. Is there a pre-made hood that is not a range hood, that would work better? Is the fan that comes with the range hood adequate at all, do you think? I know you haven't done your testing yet, so the question may be premature. Also, do you know anything about Orton kiln vents?

Re: Range Hood Ventilators
Emily -- Tuesday, 27 March 2001, at 6:42 p.m.

Vince: how far above the workspace should the hood be?

Emily

Re: Range Hood Ventilators
Stan Wolfersberger -- Tuesday, 27 March 2001, at 9:20 p.m.

FYI, I just submitted an article to the Bead Release on my research on "how much" ventilation is appropriate for ventilating a torch. While I don't want to reveal too much (I know the Bead Release is probably more forgiving about pre-publication press than science journals, but that's my training), a lot of the units out there may be a bit low on the low side.

Vince has some good tips, and if you read some of my earlier posts, and check out the State of Wash ventilation link I posted, you'll see the rationale behind this advice.

Anyhoo, more to come in the Bead Release......Stan

Re: Range Hood Ventilators
michey -- Tuesday, 27 March 2001, at 10:32 p.m.

I know one thing to consider is duct tape may not be effective. I haven't found a solution yet but I routinely have to replace all my duct tape every 2-4 weeks. Totally annoying but it starts gapping, patching works for a bit but I usually end up redoing it all. I only accidently discovered the leaks when I was up on the ladder checking other stuff. Now I check routinely. My studio is even climate controlled so it isn't exposed to the elements though I do open a door and window in addition to my ventilation but this shouldn't be enough to cause a problem.

Re: Range Hood Ventilators
Vince Henley -- Tuesday, 27 March 2001, at 11:23 p.m.

If you need to replace your duct tape every couple of weeks, something is very wrong. Normally duct tape is designed for permanent installation in inaccessable places with a life span of many, many years. Without knowing more about what you are doing I can't comment more. I have had to replace duct tape after 20 years of very bad environmental exposure, but even then it had not failed, just became brittle. The seal was still intact, and some cracking at the joint was evident where movement had taken place. However, the duct tape could not be easily removed and was simply taped over again after cleaning the surface of the duct.

Without seeing your actual installation, a diagnosis is difficult, but normally duct tape is about as permanent as you can get. They even use a variant of it for non-structural aircraft temporary repair.

Are you by chance using teflon or some industrial engineering plastic duct? If that is the case, then you will need to match the adhesive to the material, and normal duct tape may not work. Standard duct is light-gauge galvanized steel, and I can assure you that a standard certified grade of duct tape will work very well indeed on that material.

Send me an email describing your installation and I'll try to help.

Vince

Re: Range Hood Ventilators
Vince Henley -- Tuesday, 27 March 2001, at 11:37 p.m.

Emily,

that is one of the things I hope to be able to offer advice about after the tests. My test installation is about 28-29 inches above the surface on which the torch rests, but that may not be optimum. I can vary this relationship for testing and may have something to say later. Measuring something like this is not something one can do in five minutes and have dependable data, so it will just need to wait until I can instrument the setup in various configurations and run the tests. It will also depend on the angle your torch makes with the work surface, the flame velocity, the horizontal distance from the primary intake stream, the existence of baffles, the capacity of the fan, the shape of the hood, and a lot of other factors.

I'm not prepared to offer more advice right now. It sounds like Stan has done some research, perhaps he can offer more advice than I at the moment.

Vince

Re: Range Hood Ventilators
Vince Henley -- Tuesday, 27 March 2001, at 11:48 p.m.

Patti,

there are undoubtedly pre-made hoods on the market that are more effective, but I can't recommend one offhand. I don't know about the kiln vents.

The range hood fan can be adequate for some installations, but it is no giant of an airmover. If you find one that has a specification of less than 200 CFM, I would just not buy that one and find another. 200 CFM is my idea of the very lowest end one should consider and that may not be adequate for many installations. I'm thinking of the bead maker who uses a single torch in the Minor/Lynx/Mini-CC class and wants low-cost, but adequate ventilation for a small workspace. For this person, a range hood may be a good, cost effective solution, but not for a person using a Major, Carlisle, Delta or Bethlehem class torch.

I only thought to make these tests because so many people are apparently already using range hoods as their vent solution.

Vince

Re: Range Hood Ventilators
patti -- Wednesday, 28 March 2001, at 12:44 a.m.

I used duct tape one Halloween to afix a stuffed animal on my bare shoulder. I was supposed to be Joan Embry (San Diego Zoo - anyone remember her?) I didn't know any better. After 4 hours - well, let's just say there was no gapping.
Older (much) and Wiser

Re: Range Hood Ventilators
Mari Johnson -- Wednesday, 28 March 2001, at 6:01 a.m.

Patti!

I remember Joan Embrey.. blonde, with a penchant for khaki? Great costume, LOL.

Vince, thanks for doing this! I use a vent set up and some of your tips will be put into action today.I will be anxious to hear the results of your test. My studio is in my basement, which is very large, but the window where I work is very small, so I have asked my husband to look into getting a more powerful fan in that hood and he was "going to look into it". The extension at the back is a great idea, we'll tackle that this weekend.

All this talk of duct tape... anyone thinking Red Green? Vince do you wear suspenders? :c)


Re: Range Hood Ventilators
Vince Henley -- Wednesday, 28 March 2001, at 12:34 p.m.

No, Mari, I do not wear suspenders. I prefer techno-geek business casual, sans pocket protector, and I only use fountain pens. In my other life I can be found with ranch grubbbies, lots of dirt and sweat, and often a hard-hat. ;-)

Vince

Re: Range Hood Ventilators
Jay Shuster -- Wednesday, 28 March 2001, at 12:47 p.m.

One duct tape comment. Nashua brand duct tape is the best with out a doubt. I have tested many types in many situations. extreme sun, saltwater, vent duct etc. Nashua is the best I refuse to use anything else. Jay

Re: Range Hood Ventilators
Vince Henley -- Wednesday, 28 March 2001, at 3:04 p.m.

I agree. I happen to be using the best grade of that brand.

Vince

Re: Range Hood Ventilators
Lisa -- Wednesday, 28 March 2001, at 6:48 p.m.

I'm about to purchase a range hood:
250 cfm's and I have the choice of 30 or 36 inch unit. Would it make more sense to go with the narrower one, considering the venting power is the same and it would likely draw more directly from the torch, or would I be better off going for width, and drawing from a greater area. Do I need to have the kiln vented as well? It will be on the same work surface as my torch and might benefit from the 36" hood.

I love the information gained here, but unfortunately I'm the kind of person who researches things to death (I'm a researcher by profession), and keep getting caught in all this stuff without being able to commit to purchasing all my equipment. Nothing seems more important than health and safety, aka ventilation, therefore I feel a bit stymied (as I'm dying to order my torch, etc.).


Re: Range Hood Ventilators
Vince Henley -- Wednesday, 28 March 2001, at 7:36 p.m.

Lisa,

as I stated in a previous post, I am not ready to publish any numbers at the moment, and won't be until probably mid-May simply due to other commitments. I'm working the instrumenting and measurement of the test set-up into my other obligations and they are using up my time for the next few weeks.

However, let me point out that the effective capture area of the range hoods is not much greater than the area of the filter box, and that will likely be the same for both the 30 and the 36 inch models. The shape of the range hood is generally too shallow in depth to allow effective capture across its width without additional baffles and the flow of air toward the fan will drop off greatly as you move laterally away from the filter aperture, especially in a direction other than toward the source of your make-up air. That's why I recommended adding the rear baffle in my earlier post. The wider hood will help remove heat from your kiln if it sits partially under it, but I would recommend that you position your torch on the centerline of the fan and not off to one side just to accommodate the kiln. I'll have more to say about the relative positioning of torch and hood after the measurements. Ambient environmental hazards from the torch are likely to be greater than those from the kiln unless you are using the kiln for something other than annealing beads.

All other things being equal, if cost is not a major consideration, and if you have sufficient space, go for the wider hood. It certainly will do no harm and may provide a marginal additional benefit.

Vince

Re: Range Hood Ventilators
Lisa -- Thursday, 29 March 2001, at 12:35 p.m.

Thanks Vince. I guess my final (yeah, right) question (to Vince, or anyone)would be if it would be preferable to have the range hood set forward from the wall, so that it would be closer to the torch. My table is 30" deep. Am I aiming to have the vent directly over the torch?
Lisa

Re: Range Hood Ventilators
Lisa -- Thursday, 29 March 2001, at 1:03 p.m.

Me again (see, not my final response!). I have the option of purchasing either a 400 cfm unit or a 250 cfm unit. I wonder if anyone has experience using either and could inform me on the noise level. Also, is it always preferable to go with the larger unit? In this case the cost difference will be only $10, so should I just splurge and expect that the extra will be worth it? It does have infinite control, so I suppose unless it's cranked up to the highest level, it won't be using the full 400, is that right?

Lisa
(impatiently awaiting the "final range hood report")
Actually, can't wait as I must begin beading at home. 'Nuf said.

Re: Range Hood Ventilators
Vince Henley -- Thursday, 29 March 2001, at 1:47 p.m.

Lisa,

the 400 CFM model is definitely preferable. Noise can be a problem with almost any ventilation system. Ever been in a large building when the power went off? Notice the quiet? We live with such a level of environmental noise that we get accustomed to it and don't "hear" it until it is gone. However, minor noise is better than contaminated air.

You do not want the vent directly over the torch. You are trying to capture the stream of gas combustion byproducts from the torch and they have a velocity that is quite high. To get an idea of where to place the vent, take an incense cone and light it. Light your torch with your normal flame level. Set the burning incense cone on your work surface directly under the end of the torch flame so that the smoke from the cone gets picked up and carried along by the gas stream from the torch. You do not want to "burn" the smoke in the torch, so place the cone so that the smoke simply gets moved by the gas flow from the torch flame. Watch where the smoke goes. Place your hood vent and any baffles where they can easily intercept the stream of smoke. If that is not against a wall, by all means use a back baffle as described in my first post. Side baffles may also be useful. Remember that a running fan will change the airflow that you see with this experiment so you just need to be close, not exact.

Don't forget, you need a source of "make up" air with a capacity at least equal to the fan, preferably greater, or you will simply have a noisemaker, not an exhaust fan.

I hope this helps.

Vince

Re: Range Hood Ventilators
Lisa -- Thursday, 29 March 2001, at 2:45 p.m.

Thanks for all the info. The "make-up air" will be the windows in the room, I suppose. Is there a rule of thumb for judging how best to do that? I will have a window directly to my left, and one on my rear wall (the room is 12 feet deep). Also, I am only just purchasing both the fan and the vent, so I suppose I should get the burner here first before I even set up the vent. THAT WILL MAKE ME INSANE, having the equipment all here but not yet vented and ready to use. But I know it's best (oh, lord).
Lisa

Lisa,

the preferred location for your source of make-up air is from behind your workstation. That way the air flows past you, past the torch, and up and out the vent fan. Not much chance for an eddy to carry contaminants toward you that way.

Vince

Re: Range Hood Ventilators
Terri -- Friday, 30 March 2001, at 9:35 p.m.

Vince, this could not be more timely for me. I think I will wait to complete installation of my hood until I get your report. I'm planning on having a sheet metal worker build a hood for me. I have a powerful fan (Greenheck 096) installed in the roof over my work area which will be connected to the hood with smooth sided ducting. I've heard that spiral duct makes the motor have to work harder due to the air flow resistance from the irregular surface inside the duct. The idea about the baffle is interesting & one I had not thought of. I look forward to hearing your results. Thank you for sharing this with us! Terri

Re: Range Hood Ventilators
Vince Henley -- Saturday, 31 March 2001, at 2:26 a.m.

Hi Terri,

my study is specific to commonly available consumer range hoods.

If you are having a hood fabricated and have a powerful fan, there is no need to wait. You can achieve whatever airflow characteristics you desire by simply following some of the earlier guidelines and reference material mentioned by Stan. The baffle is needed only because the vertical air velocity created by the range hood fan might be less in some capture zones than the forward velocity of the combustion gas stream from the torch, permitting the contaminants to escape beyond the hood. If you don't have that situation, you don't need the baffle. For the consumer range hoods with fans in the 200 CFM class, the baffle is very useful and improves the performance greatly.

Vince

Re: Range Hood Ventilators
Lisa -- Saturday, 31 March 2001, at 5:42 p.m.

Thanks for all your help, Vince. From all your information, I've decided to order a 400 cfm unit, rather than the 250 I was planning on. I expect that adding the baffle could only help, even if I'm purchasing the more powerful unit. Thanks again.
Lisa

********************

Stan the Man and ??????: Ventilation
Barbara Simon -- Saturday, 14 April 2001, at 8:17 a.m.

Stan or anybody else that wants to weigh in: (I am building a new studio/house...notice which one I put first, hah!) Do I need to allow for more outside exhange of air flow in my ventilation equation for the use of an o2 concentrator?

I have rigged up a configuation where I can use the tank and the concentrator at the same time. My relative, who is a contruction engineer, and is giving me advice on a ventilation set up, said that I should install an "outside air in-flow" type setup near my exhaust, so that my exhaust fan is not taking all my nice air-conditioned air from the room (My space is 610 sq ft by 10 ft ceilings. My glass area will be in one corner) as I work with it (o2 con.) on. He saw my concentrator and said that maybe I should account for it's use also in the system. What is your take on that?

I just re-read this mess hope you can understand. thanks a bunch

Re: Stan the Man and ??????: Ventilation
Dave Bross -- Saturday, 14 April 2001, at 9:08 a.m.

Your relative is right. Even without the issue of the air conditining, you must have "make up" air to replace the contaminated air the vent system removes, or the removal will not be all that effective.

About the concentrator, the zeolite beds that extract the oxygen will live much longer if they can be operating in a low humidity environment, such as an air conditioned room. The concentrator doesn't put out anything hazardous, or use up much volume of air, so it's not much of a ventilation issue.

Re: Stan the Man and ??????: Ventilation
Vince Henley -- Saturday, 14 April 2001, at 2:26 p.m.

Barbara,

you need to allow for outside airflow in amounts at least as great as the exhaust capacity of your ventilation fan, whether you use a concentrator or not. Your relative is providing you with good advice on the concept, but there is another point that I will cover later. Let me repeat: Your source of make-up air must be AT LEAST as great as the CFM capacity of your ventilation blower. More is usually better, for a variety of reasons.

Air Conditioning does not normally provide for ANY outside airflow, although some units have a "vent" position. Air Conditioning is basically a refrigerator unit that cools recirculating air and thereby also lowers humidity. Using outside air in such a unit defeats the purpose.

The ideal source of make-up air is NOT near your exhaust. The ideal source is from behind your work position so that the air flow carries the combustion products and contaminants away from your work position and breathing area. If your source of make-up air is near the exhaust, you may be lowering the efficiency of your ventilation system and creating a hazard for yourself.

I think this has been covered in a number of posts, some from Stan, some from me and others.

As I mentioned in an earlier post, I should have data that is useful for these sorts of questions sometime in the first half of May.

Vince


Re: Stan the Man and ??????: Ventilation
Stan Wolfersberger -- Sunday, 15 April 2001, at 4:15 p.m.

Hi Barb,

Well this morning I really crafted a nice response, but I have yet to see it appear and thus it may be lost forever. Oh well!!

Dave and Vince are right on, must have make-up air to replace the air you are exhausting. I had mentioned this in one of my earlier Bead Release articles, as well as ways to accomplish this.

The climate zone you live in, the amount of air you exhaust, and the amount of time you use your ventilation system will be factors in whether you need to have your make-up air tempered. In my wife's set-up, we don't worry about this - we accept the fact that there is a bit of energy cost associated with exhausting the studio. If you work full-time in your studio, and live in a climate where you are in heating (or air conditioning mode) most of the time, then investing in equipment designed to exchange the air may be in order. Units such as air-to-air heat exchangers are on the market. Labortories often have some type of tempered air that provides make-up air near fume hoods - otherwise it can be downright uncomfortable working in them. You may need to get out the calculator and see whether the cost of such equipment has a pay-back period that would make this a preferred option.

Lots of other info in past posts, so use my name, Vince's or Dave's along with ventilation, and you should find some useful stuff. Ok, I'm going to zap this and not risk lightning striking twice in the same day!!!......Stan

******************

patti -- Wednesday, 16 May 2001, at 3:08 p.m.

Does anyone know who makes them? My contractor guy can only find 110cfm and 1000cfm (!!!). Thanks!

Re: 400 CFM fan
Stan Wolfersberger -- Wednesday, 16 May 2001, at 3:17 p.m.

Some of the big suppliers, like Grainger, McMaster-Carr (spelled right?) should have them. I'll bet Vince can even tell you the page number.....Stan

Re: 400 CFM fan
Vince Henley -- Wednesday, 16 May 2001, at 4:50 p.m.

Find another contractor.

Stan is almost right, but there are too many bloody pages! The W. W. Grainger catalog lists a LARGE number of suitable blowers in all types of configurations and capacities. Start at the link I've provided and browse to find one that fits your needs. I saw several in that capacity range and different configurations. Note, you need to look for something in the range, not exactly 400CFM. 400-600 would work fine. If you click on the blower model number it will take you to a page showing the technical specifications. Note that there are even in-duct blowers in that capacity range.

Your contractor should know these things.

Vince

W. W. Grainger HVAC Blowers

Re: 400 CFM fan
Stan Wolfersberger -- Wednesday, 16 May 2001, at 6:43 p.m.

Vince, I just knew that you had that catalog practically memorized!!....Stan

Re: 400 CFM fan
patti -- Wednesday, 16 May 2001, at 7:12 p.m.

Grainger has this one:

http://www.grainger.com/Grainger/pro...?xi=xi&ItemId=