Fume extraction - is this setup safe?

I have a 6 x 3 x 2.2m shed I want to use for MIG (gas) and TIG welding cold rolled and zincanneal sheet.
Shed has 2 windows on opposite sides about .5 x .5m in size.

Am looking at a system for fume extraction. The auto store is selling an extraction fan for $140.
It has a 30cm diameter and can extract 60cu m of air per minute. The shed is approximately 40cu m.

Attachment 296369

I have tested it instore and the extraction side really pushes some air. The fan can sit outside the
shed with some flexible ducting through the window inside for local extraction during welding.

My question, is this safe? My concern is the potential for sparks to get sucked through and into the electrics of the fan. Or any other satefy issues to consider?

Additionally I wanted to use this for fume extration of automotive paint in a similar setup, although outside the shed in a home made booth.
My concern here would be paint or solvent fumes being ignited by the electrics in the fan.

I have included a picture of the unit. It's quite empty inside. The electric plug attaches to the top of the unit and
there's some shielded wires down into the motor in the centre.

Also considered a simple bathroom fan but have the same concerns about the electrics igniting fumes or other
hot sparks causing safetly concerns. It's also not as powerful.

As general comments -

• Fans will only 'noticably' suck air for a short distance in front of them (air moves in to replace the air removes, but at a much more leisurely speed), so you will need some local ducting to remove fume if you have the fan outside. Having said that, make sure you don't suck your weld shield away.
• Sparks go cold pretty quickly so shouldn't be sucked into the fan such that they cause any thing to ignite. While grinding sparks will ignite things (cloth is the most common) you normally need a lot of them to get enough heat into the flammable material. Weld spatter is heavier and should not travel very far.
• You should not have any flammable gases floating around where you are welding. if you do the arc is just as likely to ignite them as a spark from a fan. People in that situation use the fan to push air into a space so that the flammables are in turn pushed elsewhere.
• Remember fume is a hot gas/ smoke and so will rise. It may be more effective to have fume extraction directly over your weld area.

Michael

I agree with MichaelG about the sparks but disagree about pulling versus pushing provided the fan can be located directly above the fume generation point then pulling the fumes will be far more effective than trying to push them out of a shed.

The flow rate for the fan won't be the manufacturers claimed rate. Most manufacturers perform a single point air speed measurement in front of the opening of these axial flow fans and multiply that by the cross sectional area of the fan which does not take into account the resistance to air flow of the sides of the fan housing. The real air flow rates will be about 2/3rds to a half of the claim.

Nevertheless 30 m³/min is worth having, although these types of fame tend to make a bit of a racket.

As MichaelG says the location of the fan is critical. If the welding fumes can be constrained even partially by using a welding booth/hood/enclosure and the fan draws on this booth/hood/enclosure then this will be far more effective at clearing the fumes than just placing the fan on a wall.

This is my small (1 x 1 m) fume hood with the 70 m³/min squirrel cage fan. The fan really does shift 70 m³/min because I measured it accurately with a calibrated air speed meter and made allowances for the resistance to air flow of the sides of the fan housing
I only run the fan at half speed but it easily keeps the 110 m³ shed free of fumes.
I can even weld small pieces of galv steel under this hood since it easily captures the white ZnO fumes from a short weld.
The booth can be enclosed with wrap around steel doors and as you can see I sometimes use it as a spray booth.
The wooden T-stand in the middle of the hood has a small lazy susan / bearing platform for rotating small objects on it while spraying
The booth is small because my shed s packed and I mainly do small jobs but the same principle applies of you are doing big work.

https://www.woodworkforums.com/attach...d=296425&stc=1

If you work with large pieces and want to vent the whole shed then the location of the fan is important.
Firstly the should be as high as possible on the wall or even roof of the shed above the main work area.
If you have a gable roof then placing the fan near the ridge cap would be advisable.
If you have a skillion roof then it would depend on how steep the roof is. For a really steep roof near the highest wall would be better but if it is a shallow roof I would just place it above the work area.
Having the two windows opposite will help but this will set up a bit of an in-out air tunnel between the windows and the fan and not clear much of the rest of the shed so I would recommend adding extra vents on the walls at other parts of the shed. Some up high near the roof and down low near the ground will help keep the shed clear of fumes.

Thanks for the detailed responses. Nice setup with the fume hood. Where do you buy those squirrel fans from? Obviously no saftey concerns with using them for painting then?

I re-measured everything and included a rough plan.
Height 2.2m with a flat roof
Window base is 1.4m from ground
Window openings are 56 x 54 cm.
Attachment 296476

Ideally welding bench would be top right corner as there's some supports already in place there, but will set up wherever is best.

Was also looking at installing a whirley bird for general shed cooling, so if I go with a hood or ceiling extraction fan then unsure of whirley bird placement.

The extractor fan I found what looks to be the same unit rebranded although it claims to have slightly higher air flow. https://www.tradetools.com/products/SHT3APC#specs

Thanks again for all the suggestions.

When planning the location of any fan, keep in mind that you don't want it blowing a gale over the welding area - you don't want it to disturb the shielding gas flow from the MIG or TIG.

With flammable fumes, any extraction should be running before any fume generation starts taking place. This way the fumes are being removes as soon as they are generate so they do not get a chance to build up and spread to all parts of a shed where they are much harder to remove. The same applies to wood or welding dusts.