Radon is a toxic, naturally occurring gas that is thought to accumulate in residence basements. Radon gas is the byproduct of the breakdown of soil containing small concentrations of naturally occurring radioactive isotopes. Soil derived from granite and other igneous rock typically produces radon, and this gas could conceivably make its way into a residential basement through cracks and fissures in the concrete slab. Does this actually occur?

To test the radon gas hypotheses, a major university conducted testing designed to determine under what conditions radon could actually accumulate in a residential basement. Several concrete vaults were installed in granitic soils. To facilitate the entry of radon, a series of radiating probes were drilled outward from the vault and fitted with screens. A radiation detector was installed inside the vault to indicate the presence of radon gas.

The radon gas will only flow into a basement if the pressure inside the house is lower than the ambient atmosphere. This condition is thought to be possible because houses are typically warm inside and a lower pressure will occur, especially during the winter months in cold climates. To simulate this very small pressure difference, the vaults were sealed and an exhaust blower was used to control the inside pressure.

A very sensitive pressure transducer was needed to sense the very small pressure difference between the inside of the vault and the ambient atmosphere.

This pressure difference might be equal to just a few hundredths of an inch of water column.