Venting welding fumes in garage workshop

[wasabi]

I do hobby welding in my 24x24 detached garage and the fumes sometimes build up during the winter when all the doors and windows are closed. I am thinking of installing a 1300 CFM gable power vent on my gable to assist in controlling fumes.

I plan to build a box around this vent fan and mount it to the gable (from the inside of course). I'll cut a 6 inch hole in the box, mount a 6 inch round vent adapter over the hole, then install some flexible duct to it. I'll mount a pass-thru type (undetermined) duct adapter in my garage ceiling sheetrock to let me add more flexible duct (6 inch diameter) so it reaches my welding table. Then I can power the vent on when I need the exhaust capabilities, or leave it off. I want this duct as the vent, and not a ceiling fan, because I don't want to vent all my warm air out of the garage during winter. This vent duct over my table is how it is done in my welding class.

Thoughts? I was gonna use a similarly powered squirrel cage blower but this gable power vent seems cheaper and is available at my small town's hardware store.

Thanks for any input, particularly on the transition through my ceiling. Also, would 1300 CFM in a 20' 6-inch duct be too much?

[wasabi]

I'm sorry - was there a protocol I did not follow for posting this question, or is it off topic? Just curious as this is my first posting experience here and I didn't get any responses. I know some boards have rules that take awhile to learn.

Thanks!

[majakdragon]

wasabi, Welcome to the DIY Forums.
No, you did not violate any rules. Being the holidays some of the experts are not online as much as usual. I am sure that you will get an answer though. Sorry it is taking a little longer than usual.

[Ed Imeduc]

wasabi stay with us your ok, long week end here for sure .
Lets kick this aroundd some 1300 CFM. Boy you need a 18"X24" intake for just 1050 CFM by my books. A 6 " pipe works at just a 100 CFM. I have use the welding vent pipes but cant recall what they work at. i do know that they would just about take the smoke away is all At 1300 CFM net you will need a make up air heater to let the air in. I think check out Grainger they have a one man unit . Works on a 2 1/5 " hose at 226 CfM . Their smoke exhausters work at 370 CFM on a 4" hose. I think you are going to big here. Id re think it for sure .

ED :thinker:

[wasabi]

Ed,

Thanks for the feedback! I suggested 1300 CFM because another fellow on a welding forum built the exact same setup and he used a 1200 CFM squirrel cage blower and an 8 inch pipe. He acknowledged I could go with a lower CFM blower if I went with 6 or 4 inch pipe, but not too much lower based on how his works. I don't know myself....looking to run his by some experts here! He did some calculation and thought 700 CFM would be adequate for the 6 inch?

He responded to my email and thought the gable vent fan might not provide adequate pressure to suck the air up through 20 feet or so of 6 inch hose. This is why he suggested I get a squirrel cage blower. He said the gable fan might have the right CFM rating, just not enough power.

Do you think a ~1000 CFM gable fan with a box around it would be OK? I accept there will be some CFM losses pulling up through 20 feet of hose, but all I need is 350-700. I can get one easily at Lowes, or I would have to order a squirrel cage blower from either Grainger or some guy has lots of good ones already set up on ebay.

THANKS!!

[Ed Imeduc]

In Grainger they say 1040 CFM 8 " pipe 10ft
And list a 226 CFM at a 2 1/2"pipe 10 ft.
See if you cant run down one of there cat. has a lot of info on the fans and how and what you need. DVont forget you need the air in also. like have built hoods for this and big kitchens. Put a in fan just 100 cfm light of the out fan. This will help keep the heat are cool in the building.

ED ;)