A system configured to deliver dry pressurized air, derived from ambient air, to underground or outdoor cables, conduit, waveguides, plenums or other air spaces for the purpose of preventing the ingress of moisture or contamination. The system includes a housing and a modular membrane pressurization unit removably received within an interior space of the housing. The housing has a base configured for being at least partially buried below ground level and an air intake above ground level. The modular membrane pressurization unit intakes humid ambient air from the environment surrounding the housing and generates a continuous supply of dry pressurized air housing that is routed to the underground air space.