Zinc fume respiratory protection.

[S. Heslop]

Spent a bit of today reading up on investment casting, to cast various hardware for banjos.

They'd have to be made out of brass, since that's what's expected. And being very hot brass, i'd prefer to do it with a partner (I learned my lesson when I tried juggling the entire operation with aluminium). If it was just myself i'd consider holding my breath and standing up wind of the crucible, but with somebody else involved i'd have to go all out on safety.

I've been googling about trying to see if I could find anything on respiratory protection for zinc fumes, but didn't find much. I should've wore respiratory protection when I blew the layer of dust off my Cromwell tools catalogue, but all it said for the filters in there was protection from 'fumes'. That might include zinc but I'd prefer something more concrete.

What kind of filter rating would be required for protection against zinc fumes?

Also, while i'm at it, where's a good place in the UK to buy silicon rubber for mould making?

[Pete W.]

Hi there, Simon,

I've seen pictures of a respirator that has two flexible pipes that go over the wearer's back.  Presumably one for inhale and the other for exhale and with appropriate non-return valves.  I've never used one but it seems sensible to draw one's breathing air from somewhere remote from the fumes.

A neighbour of ours is a welder and is occasionally faced with the prospect of zinc fumes, e.g. from galvanised jobs whose zinc coating hasn't been completely removed in the welding area.  When that sort of work is imminent, he drinks lots of milk - maybe that's just superstition, other Modders may be able/inclined to comment on that. 

[tom osselton]

Well they talk about it here and say you can use a p100 filter for welding zinc I'll go to the safety store and see what they say about it. Another thing is not to use compresor air for a breathing source the oil will coat your lungs and kill you.  I am thinking about a stove pipe suspended over the exhaust vent that can be rotated out of the way for filling /removal of the crucible until then I will watch the wind direction and hold the breath while filling the crucible I just did two melts of yellow brass with no ill effects however the first time casting it I did for couple days.
Just thinking what about a rebreather probably just a brainfart!

http://www.finishing.com/85/35.shtml

[S. Heslop]

I didn't like the sound of forced air hoses either, not when stumbling around carrying crucibles of hot metal.

I have P3 filters (EU equivalents to P100) for both my respirators but I never felt they were doing that good a job since I could smell whatever wood i've been cutting. Might just be a case of an ill fitting respirator though, or maybe oils in the wood evaporating. Maybe I could do a stupid test by welding some galv steel while wearing one, zinc fumes have a distinct smell. I guess i'll try that tomorrow when it's light.

Thanks for the help!

[awemawson]

When I'm grit blasting I wear a proper Apollo air fed helmet that is supplied via it's own regulator, and a very large floor standing filter. This is Clemco's standard set up and I've never heard comments via oil in lungs (though I can see the potential problem). I presume that the element in the filter holds it back

[S. Heslop]

At the boot sale today was a full SCBA rig, minus the cylinder. I was oh so tempted to offer a price but was frightened I'd get a bargain. I find it weird that i've reached a point where i'm hesitating to buy more junk, since i'm running out of space. I've got boxes of rust from boot sales that I keep thinking i'll clean up some day. Maybe I should start throwing out the old junk so I can buy new junk.

[vtsteam]

Welding respirators for metal fumes:

http://www.capitolscientific.com/lab-safety-products/3m-welding-fume-particulate-respirator

I believe milk has been used because the calcium may displace the zinc in the body -- calcium has been used in that way in the past for other metal inhalation problems. Not sure where I recall that from.

[lordedmond]

At the iron works many years ago you got two liquid issues from the firm
The less common was milk , for when you had been wearing a air fed gas mask on the charging platform of the blast furnace , not sure of the reason

The other was 8 pints of beer per shift , reason it was to replace the fluid you lost in the heat from the molten iron , it was fetched from the works pub by the bucketful . The firm had it's own pubs one for each works and they were open for a stores issue of beer 24/7

The other funny one was salt tablets

It was also common for the welders to claim a stores issue of milk , that was for any welding work note this was before H&S or the EU stuck their oar in

Stuart