The invention relates to an electrical installation, especially a medium-voltage switchgear, comprising at least one encapsulated function module (FM), a decompression channel (DK) which is connected to said function module, and at least one inflow opening (EO . . . ) which connects the function module (FM) to the decompression channel (DK). The covering surface (DF 1,2,3) of the decompression channel (DK), opposite the inflow opening (EO . . . ), comprises at least one partial region which is obliquely oriented in relation to the inflow direction. Hot gases and high pressures produced during an accidental arc can thus be evacuated from the installation, without any risk to humans and buildings. Pressure channels are used, inter alia, in installations used in relation to medium-voltage technique for providing and distributing energy.