Minnesota homes commonly operate under a negative air pressure, especially during the heating season. What this means is that the air pressure inside your home is typically lower then the surrounding air and soil, and this creates a vacuum that pulls soil gases, such as radon, into the home via pathways. Even if the ground around the house is frozen or soaked by rain, the gravel and disturbed ground underneath the house remains warm and permeable, attracting radon gas from the surrounding soil.