The Swiss Civil Defense system forms part of the national defense, has no combat tasks, and aims at the protection, rescue of, and care for the entire population of Switzerland. Horizontal evacuation is considered impractical and unrealistic. Vertical evacuation into special shelters in homes, public buildings, factories, etc., is the focus of CD. planning efforts. Shelters have increased air pressure, are artificially ventilated, are equipped with gas filters and are strong enough to give a relative protection against outside pressure, irradiation, chemical contamination and missile fragments of conventional weapons. The Swiss CD. system is to ameliorate the direct or indirect effects on the population of conventional, chemical, or nuclear war.