What device is used to quantitatively measure sub-slab pressures?

The appropriate device for quantitatively measuring sub-slab pressures is a micromanometer. This tool is specifically designed to measure small pressure differences, which is critical in the context of radon mitigation and monitoring. Micromanometers are highly sensitive and can provide precise readings necessary to assess the effectiveness of radon mitigation systems and to ensure that sub-slab depressurization techniques are working properly.

While pressure gauges and electronic pressure sensors can also be used to measure pressure, they may not offer the same level of precision for small variances as a micromanometer does. A manometer is generally more suitable for measuring larger pressure differences and may not provide the detailed information needed for monitoring sub-slab conditions effectively. Thus, the micromanometer's capability to measure subtle pressure differences accurately makes it the best choice for this specific application in radon mitigation practices.