At Fortune Ltd our  stock radon sumps comprises a cavity about the size of an A4 folder in the ground immediately under the floor slab that is open to the surrounding under-floor hardcore and linked by
pipe work to the outside. Radon sumps opperate by reversing the pressure differential between the space under the floor and the room above. The radon-laden air coming from the ground is drawn out from under the slab by an electric fan in the pipeline and so is prevented from entering the occupied indoor space . Externally when Radon exits the ground it will quickly diffuse/dilute into the atmosphere not allowing for any high concentrated levels causing harm.