Like the European ceramic stove, the heat-retaining capacity of a massive block of masonry is tremendous. So while it might take several daytime hours of heating to reach its desired surface temperature, the bed would remain warm throughout the night even though nobody arose to feed the fire.
The first type of heated platform appeared in China is using the single flue system. This type of heated platform is unearthed in the 1st-century building remains in the Heilongjiang Province. Its single flue is 'L' shaped, built from adobe and cobblestones and covered with stone slabs.
Heated walls with double flue system is found in the 4th century ancient palace building in the Jilin Province. It has an 'L' shaped adobe bench with double flue system. It is structurally more complex than single flue system and has the functionallity close to the Kang.
Outside China, the concept of a "masonry heater" - a large stove made of brick, and keeping a house warm for a long time - has been known in various forms throughout northern and eastern Europe. In particular, Russians have traditionally used a similar sort of stove/bed, known as the 'Russian stove'; it is unknown whether this was introduced from the East during the period of the "Tatar yoke".
The Kang was also an important feature of traditional dwellings in the often frigid northeastern region of Manchuria, where it was known as nahan in the native language of the local Manchus. It plays an important role in Manchu's mourning customs. The deceased is placed beside the Kang instead of the normal chinese practice which is in the central hall. The height of the board on which the body is placed indicates the family status or age of the deceased.
In this picture of a room in a Chinese inn, reproduced from Wandering in Northern China, by Harry A. Franck (Copyright 1923 by the Century Company of New York and London), one can see a man who may be the author sitting at a short-legged table that has been placed on the Kang. Behind the Kang is a fine window that lets much light into the room. The window appears to be closed by a paper-covered lattice, not a pane of glass