[Stoves] At what temperature are the bad gases from zinc created, vs harmless zinc oxide?

[Paul Anderson]

Stovers,

I think that Hugh is not on the Stoves Listserv and cannot post 
messages.   So I am forwarding his reply to all of you.

In response to Boston's comment, he is correct about the parts of the 
stoves that are NOT in the direct pyrolysis and combustion pathways.  
The galvanizing will remain intact if surfaces are under 200 C.

Thanks to all for the responses.

Paul

Paul S. Anderson, PhD  aka "Dr TLUD"
Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
Website:  www.drtlud.com

On 2/1/2013 2:08 PM, Hugh McLaughlin wrote:
> My perspective on this is it takes real stupidity to be harmed by 
> galvanized stove parts.
>
> The core concern is arc welding galvanized material - which vaporizes 
> the zinc metal rapidly enough that it does not oxidize to zinc oxide. 
> Then you have to breath in the zinc-laded smoke - again rather easy to 
> avoid. The same effect happen in spot welding, but in smaller quantities.
>
> If you are exposed, you get a flu-like response. See 
> http://en.wikipedia.org/wiki/Metal_fume_fever
>
> The real issue is processes that deal with molten zinc, such as when 
> casting zinc. But even then, the risks of burns outweighs the zinc 
> inhalation concern.
>
> For stoves, a slow heating of the galvanized surface in the presence 
> of air will oxidize the surface and render it less scary. However, it 
> should be noted, that if you lick the zinc oxide off the ductwork, you 
> will get the same metabolic effect.
>
> I recommend the same precaution for galvanized materials as I do for 
> any painted materials or recycled tin cans - burn the completed unit 
> first time outside in a well ventilated area - and avoid sucking up 
> excess smoke. Your lungs will tell you when something is disagreeable, 
> and react accordingly.
>
> Hugh McLaughlin, PE
> ------------------------------------------------------------------------
> *From:* Paul Anderson <psanders at ilstu.edu>
> *To:* Discussion of biomass cooking stoves 
> <stoves at lists.bioenergylists.org>
> *Sent:* Friday, February 1, 2013 2:38 PM
> *Subject:* At what temperature are the bad gases from zinc created, vs 
> harmless zinc oxide?
>
> Stovers,
>
> Galvanized metal in stoves gets mentioned occasionally.  Do we have a 
> clear answer about what is the temperature at which the zinc makes 
> poisonous gases (such as when welding) versus making zinc oxide (the 
> white stuff that you can by in a tube to put on your nose to prevent 
> sunburn)?  Is it bad if the temperature is at 400 C to 700 C?  Or does 
> it need to get much higher?
>
> Paul
>
> -- Paul S. Anderson, PhD  aka "Dr TLUD"
> Email: psanders at ilstu.edu <mailto:psanders at ilstu.edu> Skype: paultlud  
> Phone: +1-309-452-7072
> Website: www.drtlud.com <http://www.drtlud.com/>
>
>
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20130201/0d58784a/attachment.html>