Every house is different with its own unique characteristics. An experienced radon professional knows to choose the right "fan size" for your system. In many cases this is based on diagnostic testing that is performed before or during installation. More experienced radon experts have learned what fans operate best under the right circumstances without the need for pre-installation diagnostics.Regardless of the approach, it is critical for the client for the mitigator to make sure the "proper" fan is chosen. On tight soil medium homes, not enough fan strength may cause it to burn out prematurely. Too much fan for a home means the home is spending too much money on electricity! The "brand" of fan makes a difference too! Some brands produce more vacuum (great CFM) than their competitive counterparts. Some fans are colored a UV resistant "gray" while their competitors's WHITE fans turn "a dull yellow" after a few months. Others require the use of a "fan bypass" to route condensation around the fan to keep it from passing through precious fan components that are not weatherproofed against moisture. Moisture"inside" a fan is never good and frequently causes the fan to fail prematurely.
"Manometer gauges" are required to be installed on all indoor systems (as a visual indicator that the fan is working) and to help ensure that the fan is operating with the fan manufacturer's recommended guidelines. Some companies choose fans because its the "cheapest" fan for the mitigator to purchase but it MAY not be the BEST choice for the client! Ask your prospective mitigator to explain WHY he chose the fan that he did for your system and to demonstrate that its operating properly within these mfgr guidlines! Contractors who offer "low ball prices" rarely worry about the fan they put on. Most figure they will be "long gone" before the fan fails!