What's In Oven Exhaust?

Q. I’m a manufacturer of ovens, washers, booths etc. and I am trying to get a coating facility off the ground as well, in Wooster, OH. I have a meeting with the city this week concerning the operation. I’ve got the wastewater issue under control, but when they ask “what’s going out the oven exhaust?” I don’t know the answer! How do I answer that question?

Where can I get solid information that they can read for themselves? T.B.

A. The exhaust from a powder oven includes by-products of gas combustion and some trace gases from the powder. The exhaust will have reduced oxygen content and combustion by-products that include some carbon dioxide, trace amounts of carbon monoxide and a small amount of nitrous oxide. If the gas is dirty, there may be some sulfur oxide. These gases are the normal by-products of burning natural gas, and the volume is very low.

The products released by the curing powder depend somewhat on the type of powder being cured. A typical epoxy is almost 100% solids and does not release traceable amounts of gas. TGIC polyesters release a small amount of benzene, some isophorone diisocyanate (IPDI) and polyester oligomers. Urethanes release some polyester oligomers, and primid-based powders release some water vapor.

It should be stressed that all of these materials are in very small volume, well below threshold limit value (TLV) levels. A typical powder has 95–98% solid content, so there is not much that becomes volatile in the oven.