System for regulating the breathable air in a closed space and vehicle or vessel provided with such a system

The present invention relates to a system (1) for regulating the breathable air in a closed space (2), comprising an air intake opening (3) for taking in ambient air (4) from outside the space, a measuring system for measuring a predetermined condition, a control system (8) for supplying intake ambient air (4) to the space (2) as breathable air via an air filter (6) or closing the air intake opening (3) and supplying breathable air to the space (2) from a reservoir (7), both subject to the measured condition. The invention also relates to a vehicle provided with such a system.