A specific concern to a vacuum furnace user is processing critical work during summer months with high temperatures and high humidity. This same concern could also be a problem on rainy winter months. Under these difficult conditions, it is most important to understand the impact that humid conditions can have on the final surface condition and appearance of the processed parts. Work discolored or oxidized by residual water vapor is unacceptable and must be controlled for many critical components like aerospace parts or medical implants and instruments. This paper will try to explain factors relating to humidity, air temperature, and methods to improve final product appearance and minimize possibility of contamination.