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Fumes from gas kilns

Carbon monoxide (CO) is the principle hazard of firing a gas kiln - the same as a gas kitchen stove, water heater or house furnace. A gas kiln, by the necessity of achieving combustion and an even atmosphere and heat distribution, must rely on the chimney to draw air in through the burner ports and pull it through the ware. It is a negative pressure machine, rather like a dust hood. As a result, it is effectively acting as a fume hood. The degree to which it is functioning properly is all about damper adjustment, chimney function, and gas-to-air ratio (gas furnaces take advantage of this phenomenon). Fumes from materials containing heavy metals are generated in the latter stages of firing where it is most important that the kiln be functioning properly or temperature will not be reached (thus fumes are drawn up the chimney). However when back pressure is sufficient, products of gas combustion can be drawn into the room. Cobalt metal fumes at the least of your worries when this happens! Electric kilns are more concerning because the fumes they generate are exclusively a product of the decomposition of materials in the bodies and glazes.

CO poisoning is a genuine hazard. Follow the instructions of the kiln manufacturer carefully. Having a carbon monoxide detector installed in the kiln room is obviously as good idea. If your kiln is fitted with a sensor that measures the degree of reduction that is an extra level of protection.

Fumes can be generated from metal oxides and carbonates of lead, manganese, cobalt, copper, chrome, iron, silver, vanadium. Likely you are not even using most of these. However, keep in mind that car exhaust contains most of these and more.

By Tony Hansen Follow me on

Related Information

Do gas kilns produce silica dust?

Are neighbours paranoid about your kiln filling the air with silica dust? Silica is not volatile and does not produce fumes from a kiln. The silica is reactive during firing, busy forming silicates in the glaze and clay body. Silica and silicates make up more than 60% on the earths crust. Your neighbour is exposed to more silica dust when taking a walk, sweeping a floor or gardening than from the stack of your kiln. Gas kilns put out carbon and sulfur compounds, like a car, when fired. These come from the fuel, but also from carbon and sulfates in the clays and glaze materials, as these decompose during firing. Potters make rocks. Rocks are stable, they endure millions of years. If your neighbours want totally clean air they need to move to a place where there are no cars.

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