# ZnO spontaneous combustion during transport

I found your contact information researching $\ce{ZnO}$ reactions. I was hoping you could please help me or orient me in the right direction to find an answer to my problem.

The company I work for produces brass alloys in a furnace and one of our byproducts is zinc oxide dust. We sell this zinc oxide to other manufacturers. The last shipment we sent on a truck combusted, it burned out of the plastic bag, burned the wooden pallet it was on and it burned a hole in the wooden bed on the truck.

This has only happened twice in the 30 year span of the company. We keep our zinc oxide for two weeks before we sell it, to make sure it has cooled down, we also use two plastic bags, closed off with tape to avoid contact with moisture.

Based on a past profile done on our material, some of the other elements found in our zinc oxide dust are: $\ce{H2O}$ 1.92%, $\ce{Cd}$ 0.13%, $\ce{Cu}$ 0.66%, $\ce{Fe}$ 0.17%, $\ce{Pb}$ 7.43%, $\ce{Mn}$ 0.01%, $\ce{K}$ 0.36%, $\ce{Na}$ 1.18%, $\ce{Ca}$ 0.06%, $\ce{Mg}$ 0.01%, $\ce{Al}$ 0.02%

Do you have any idea what could have caused this reaction? Can you please suggest a source I can look into for more information and answers? We don’t want to risk shipping this substance if there is a chance it will combust and put people in danger.

• That is very strange... D0 you have any additional info? Also there was that much Pb? – Mithoron May 9 '16 at 19:55
• For a problem of this magnitude might I suggest that you also hire somebody qualified to look into it - we are all more than willing to help but ultimately you shouldn't trust random people on the Internet who aren't privy to the actual situation etc. All we can offer are suggestions. (And personally I find it very strange too.) – orthocresol May 9 '16 at 20:38
• Zinc hat a relatively low boiling point of 904°C. So it might be that the zinc oxide contained significant amounts of finely dispersed zinc, which can be pyrophoric in the presence of air (or probably even moisture). However, this is only a guess. If you want to find out the true reason for the accident, you should follow @orthocresol 's suggestion and hire a professional. – aventurin May 9 '16 at 21:02