Accucraft & Aster AP-28202 Draft fan (blower) for alcohol fired models. This version has magnetic covers that are easy to remove, it uses standard 1.5v AA batteries (not supplied).
For any alcohol or coal fired steam models you need to draw the heat through the boiler, for this purpose you use a "blower" to force draw the fire, it draws the fire from cold until you raise enough steam to turn on your locomotive wear the exhaust draft then draws the fire for you as it runs.