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.