the tumbler and its contents are heated to 100 °C. The wet steam that results purges the system of air and is the only remaining atmosphere in the tumbler. As wet steam exits the tumbler, it is mechanically compressed (hence the name) to extract water vapor and transfer the heat of vaporization to the remaining gaseous steam. This pressurized, gaseous steam is then allowed to expand, and is superheated before being injected back into the tumbler where its heat causes more water to vaporize from the clothing, creating more wet steam and restarting the cycle. Like heat pump dryers, mechanical steam compression dryers recycle much of the heat used to dry the clothes, and they operate in a very similar range of efficiency as heat pump dryers. Both types can be over twice as efficient as conventional tumble dryers. The considerably higher temperatures used in mechanical steam compression dryers result in drying times on the order of half as long as those of heat pump dryers. Convectant drying Marketed by some manufacturers as a "static clothes drying technique", convectant dryers simply consist of a heating unit at the bottom, a vertical chamber, and a vent at top. The unit heats air at the bottom, reducing its relative humidity, and the natural tendency of hot air to rise brings this low-humidity air into contact with the clothes. This design is slower than conventional tumble dryers, but relatively energy-efficient if well-implemented. It works particularly well in cold and humid environments, where it dries clothes substantially faster than line-drying. In hot and dry weather, the performance delta over line-drying is negligible. Given that this is a relatively simple and cheap technique to materialize, most consumer products showcase the added benefit of portability and/or modularity. Newer designs implement a fan heater at the bottom to pump hot air into the vertical drying rack chamber. Temperatures in excess of 60 ºC can be reached inside these "hot air balloons," yet lint, static cling and shrinkage are minimal. Upfront cost is significantly lower than tumble, condenser and heat pump designs. If used in combination with washing machines featuring fast spin cycles (800+ rpm) or spin dryers, the cost-effectiveness of this technique has the potential to render tumble dryer-like designs obsolete in single-person and small family households. One disadvantage is that the moisture from the clothes is released into the immediate surroundings. Proper ventilation or a complementary