Abstract: An oxalic acid vaporizer has a modular configuration, having a dispensing module and a manually detachable heating module. This modular configuration allows the first heating module to be easily separated from the dispensing module and a substitute heating module attached to the dispensing module, thereby allowing for a very fast replacement of the heating module in the event there is a failure or overheating in the first heating module. The substitute heating module may be a duplicate of the first heating module or the substitute heating module may have a more powerful fan, be capable of greater heat, or it may be of the type having a proportional-integral-derivative controller for controlling temperature. The modular configuration provides for a continuous oxalic acid gas treatment of bee hives by allowing an operator to change out heating modules in a matter of seconds.