The three ＇class A geometries＇ in ignition theory - the sphere, the infinite cylinder and the infinite slab - are utilized in heating experiments on sawdust, which represents wood waste. Results obtained are shown to be wholly consistent with results for the same material in cubic samples, the shape most commonly used in assessing self-heating. The activation energy is determined and an extrapolation to predict the maximum safe stockpile height is performed. The infinite cylinder results are examined and extended in order to make predictions concerning storage of susceptible materials in cylindrical silos.