and yet more bad ventilation

oxwife · #1 2009-09-18, 8:21pm

i'm looking for some advice!

my exact set up seemed to work fine three years ago... which is the last time i worked glass. i have an old range hood (19" by 28" inches approx) over my set up and a dayton squirrel cage fan ( 465 CFM) attached to that. there is only one gentle curve from the top of the range hood to the fan, which is less than two feet away. the draw seems good: incense goes up no matter where i place it under the hood, and when i put a small piece of paper an inch away from the opening, it is sucked right up.

two weeks ago, i finally got my studio back up and running, and i'm pretty certain my ventilation no longer works for me. maybe the difference is that i'm spending more time at the torch (twenty hours a week instead of about five to ten).

what's been happening is that i've been getting a very minor sore throat and a metallic taste in my mouth while working glass (and it lingers afterwards). it didn't happen the first week, but the second week i started to notice it. obviously, i've stopped working glass for the time being... until i can get something worked out.

i was so excited to start working glass again, and i'm pretty discouraged about this. i want to make beads, but i don't want to put my health in jeopardy.

do you all think this could be fixed by putting one of those shield things (barley box?) around my space?

i do have another fan, but it is an emerson 1/3 HP, 1075 RPM (i don't know the CFM), and i think that might be so huge it would suck my flame away. this motor does say it has four speeds (although it only has two switches, so my husband might have to monkey with the wires?), so maybe i could make it a little less intense. does anyone know if a massive fan like this could work?

thank you for reading this, and for any help you can give me!

oh, one other thing... i do have a good air source (open door) entering my room, and it's more than twenty feet away from where the fan exhaust exits.

Dale M. · #2 2009-09-18, 8:41pm

Upgrading to the "barley box" configuration would be a big improvement... Being as you have a window behind work area for natural light, you may want to place a back and sides on hood to form the "box" by using some clear acrylic sheeting.........

Also check ventilation to see if there is no obstruction in system (birds nest in exhaust area?) and have you remembered to provide makeup air while torch/ventilation is in operation........

Basic calculation says your 465 cfm blower is right for your hood.... But remember if you change to barley box configuration, you change the "face opening" size of your "hood" and it will probably mean you need to increase size of blower...

Dale

oxwife · #3 2009-09-19, 12:49pm

thank you, dale, for your input. i see you a lot as i'm browsing around this site, and i think it's awesome that you are willing to give of your time and knowledge!

i just checked, and there is no obstruction anywhere in my system. i also sprayed a bunch of air freshener above my torch, went outside and the smell was strong where my exhaust comes out. came back in thirty seconds later and the smell was completely absent from my work area. so i know the dang thing is working properly.

i'm probably just one of those weird over-sensitive individuals... and i seem to have gotten worse over the years!

i will get the barley box up and running soon (thanks for the acrylic sheeting suggestion!), and then switch over to the bigger fan. if it isn't too big. from my description of it in my first post, does it sound like something this size would even be an option for me?

NMLinda · #4 2009-09-19, 12:54pm

Might be an obstruction, as Dale notes, but I doubt you're getting anywhere near 465 cfm from your fan, regardless: the flexible vent ducting you're using is astonishingly lossy. Whether you continue to use this fan, or if you find you need to upgrade to a bigger fan, as Dale notes, you should should replace the fex ducting with smooth-walled ducting. It's way easier to work with than folks think - the sections just push together, and the straight sections are really easy to cut with tin snips. Trust me, it makes a HUGE difference!

Linda

oxwife · #5 2009-09-19, 1:00pm

thanks linda,

awesome advice. i had no idea such a product existed. i'll have my husband get on that this weekend!

NMLinda · #6 2009-09-19, 5:07pm

You can find the smooth-walled ducting in the same general area of places like Home Depot or Lowes as the flexible stuff. Typically near plumbing

Linda

laserglass · #7 2009-09-21, 6:42am

where does your make up air come from? your ventilation will not work without it. you should have a dedicated make up air duct to the outside, and not count on an open window.

also you could really use some baffles extending downward from your hood to your work surface.

NMLinda · #8 2009-09-21, 9:34am

Important point by Mark on make-up air!!

To be sure you have the right-sized fan for your hood, a good resource is the following:

http://mikeaurelius.wordpress.com/ventilation-primer/

This site also has resources on make-up air, as does the following site (which has other excellent info, too)

www.ArtGlassAnswers.com

Just as an example, if you turn your hood into a barley box as Dale and Mark are recommending (with which I hole heartedly agree), and if you happen to have it mounted 26" above your work surface (just a guess based on your photo), the fan size you would need to have is

506 cfm = (28"/12" x 26"/12) x 100

This is what you need at the opening to the barley box, after the static pressure losses contributed by your vent ducting. The Wordpress link will take you through how to estimate that. Essentially it means that you need to upsize your fan's cfm enough to overcome those static pressure losses, so you actually need a bigger fan than 506 cfm. To know how much bigger, you need to know the manufacturer's specifications for how the cfms of the fan you need change with static pressure. Some folks add another 10% to this final cfm to add a little margin.

Bear in mind that the cfm calculation, above is based on a guess of the height of your hood above your counter - you'd have to measure it and substitute the correct number, then go through the Wordpress primer to work through the fan size you need to get that cfm at your barley box opening. A couple of things to keep in mind as you do so: 1) the fewer the bends and the bigger the diameter of the smooth-walled vent ducting, the lower the static pressure and the less you need to up-size the fan cfm and 2) the lower you can comfortably drop the hood to the worksurface, the lower the final cfm at the barley box opening you need.

Linda

Kalera · #9 2009-09-21, 10:13am

Another possibility is unrelated to the ventilation... how long have your torching sessions been, and do you drink water during them? I used to have similar symptoms while torching, and it turned out that I was simply getting dehydrated during long torch sessions, and misinterpreting the symptoms, especially the sore throat, which can take a while to go away.

oxwife · #10 2009-09-21, 2:17pm

thanks linda, for the links and cfm information. i will be switching out to my much bigger fan (i don't know for sure how many CFM, but from others on the net, that are also 1075 RPM, 1/3 HP... i think it's plenty big!).

and i will take all of your advice on creating something that extends down from my hood.

mark, my make up air is an open door to the outside world. is that not sufficient? if not, what if i put a fan by the door, pulling air in?

kalera (who i notice also lives in oregon!), i'm only working about three hours at a stretch. BUT i notice that my face does get a little bit of a "sunburn" at the torch (and i don't think i'm any closer to the flame than anyone else), so maybe it's the heat getting to me. i will try to drink more water just in case!

thanks guys!

GlassyEyedGirl · #11 2009-09-21, 2:23pm

I have a fan that is as large as the bigger one you are putting in... I would definitely recommend doing it, I think you will be happier.... and healthier!