This series of heaters features devices in three different sizes conceived for use in rooms of various dimensions. The tall version is suitable for large living spaces, the medium-sized version for small- to midsized bedrooms, while the small version can be placed, for example, on a desk. The air channels are arranged in such a way that the air is expelled vertically, thus solving the problem of low heating performance found in conventional heaters. As the heaters are column-shaped, they require only little floor space.