The air conditioners without outdoor unit are of the monobloc type, consisting of a single component that acts as a terminal and generator.
To use this type of air conditioners, one or two pass-through holes on the external wall are required, in order to dissipate the heat produced by the work of the compressor.
They are decisive in contexts where it is not possible to install the outdoor unit due to urban planning or condominium constraints. Consequently they are a valid solution for buildings of historical prestige as they have zero architectural impact.