Garage fume extractor.

[pondy]

Been wanting to get some sort of fume extractor in my garage as when im arc welding or plasma cutting it gets rather smokey inside, don't want to leave door open as get a lot of passers by who I don't want looking in at all my expensive equipment. It's a standard size garage but is in a block of 3 and mime backs on to someone else's garden. Easiest way would be to go right out the back wall were I do my welding but can't be done due to this.

I plan to run 3 metre of flat duct along the roof ( has to be flat has limited roof space with up and over door, if only rafters went the other way) into a fan then 2 metre of semi rigid aluminium duct which I can move to what ever area I wish. As it's a long run I don't know what size fan to go for, looked at some hydroponic stuff on eBay, ranging for 4 to 6", 300 to 700 m3 per hour. Is the biggest fan I can get be my best option?

Sam

 

[MattF]

The bigger the fan the better, IMHO. 4" is ne'er use nor ornament, in my opinion. Tried that in the past, and it's about as effective as a fart in a hurricane.

 

[cumbriasteve]

What material is the roof made from, if it's the big 6 sheets or similar you can get a profiled vent which would allow you to extract straight up from the area you weld at.

 

[pondy]

Something I Didn't consider,a great idea. It's just a normal flat roof,sheets of ply wood

 

[Gareth J]

The bigger the fan the better, IMHO. 4" is ne'er use nor ornament, in my opinion. Tried that in the past, and it's about as effective as a fart in a hurricane.

Ah, depends on the fan and how you're using it. A 4" ducted squirrel cage type fan used for point extraction will shift some soot. An inline pantsie bathroom extractor fan won't.

If unrestricted by space or money for bigger ducts I'd go hvlp every time, it's quieter and you can make a big fume hood. But if you're stuck for diameter, you can get good flow through a small duct with enough pressure.

 

[cumbriasteve]

Something I Didn't consider,a great idea. It's just a normal flat roof,sheets of ply wood

I would just use something like this:

https://www.roofingsuperstore.co.uk...raction/oft-1f110-flat-roof-ventterminal.html

Jigsaw out a hole, good layer of silicone, screw it done and job done

 

[CRS51]

Evening all, finally got my extraction system working at home, the workshop is 2.4m wide by 2.2m high and 11m long. I bought the fan off evilbay and got the six inch plastic duct from a clearance yard and the tapered adaptor is a plant pot !
All works well and blows directly through the wall into a 6 inch louvered wall plate to stop the back draft. I think the fan is rated at 900cu m/hr. Works well !

 

[chevy2]

I use an approx 350mm wall mounted plate fan in my 40sq m workshop,
it'll clear a smoke filled workshop in a couple of minutes,
diameter is king when it comes to moving air.