Abstract: The Voluminous amount of data than can be collected by automatic data acquisition systems during large scale fire tests requires the use of a digital computer for the reduction of data. RAPID is a stand-alone program specifically designed to convert raw instrument voltages collected during such tests into meaningful units. The reduced data can also be used alone or in combinations to obtain quantities that require more than minimal data reduction. The program is written with the ability to accept data from a user defined data acquisition system, with the ability to check the correctness of data included. Through the use of input data provided by the user, the data can be converted into meaningful scientific units. The data can then be presented in tabular or printer plot form, or stored for further processing. This user's guide provides detailed instructions for the use of the program.