ABS from 3D printing is pretty tough. BUT, the fan is sitting on the cold air intake and far enough away from the hot pipe, is should stay cool enough. You could also give it an additional distancing with nuts or just metal bars holding the fan so not only cool air from the fan but also around the hole where the fan blows into the pipe would keep it even cooler.If the box is almost 500 degrees on top, how is it not melting the plastic fan housing through conduction?