This part of ISO 8130 specifies a method for the calculation of the lower explosion limit of a coating powder, i.e. the minimum concentration of the coating powder in air which will form an explosive mixture. It is based on the knowledge of the gross calorific value of the product, as determined by the method described in ISO 1928, or on the gross calorific values of the constituents of the product.Reliable methods for the measurement of this quantity require the use of special apparatus which may not be readily available. A method for determining the explosion indices of combustible dusts in air is given in ISO 6184-1. This method is, however, very intricate, requires considerable expertise and is expensive. The calculation method leads to lower explosion limits which have been proved in practice to be satisfactgory when applied to coating application plants.