Tumbler dryers continuously draw in the cool, dry, ambient air around them and heat it before passing it through the tumbler. The resulting hot, humid air is usually vented outside to make room for more dry air to continue the drying process. This design makes no effort to recycle the heat put into the load, and thus is considered environmentally wasteful. Nevertheless, it is simple and reliable, and therefore has been widely used. Improvised methods of salvaging this heat for in-home heating, by use of inline vent boxes equipped with a flapper valve to redirect moist heated air to indoor areas, will also increase humidity within a dwelling.The great variety of spare parts poses the biggest challenge, since the availability of parts.process reliability have to be guaranteed.This can be accomplished through accurate and timely delivery either through preventative maintenance measures or in case of emergencies.