What occurs during sequential short-term testing if the first test reads 4 pCi/L or higher?

When a sequential short-term test results in a radon level of 4 pCi/L or higher, it indicates an elevated radon concentration that warrants immediate attention. In this case, the recommended action is to conduct a retest using another short-term test right away. This is crucial for confirming the initial measurement and ensuring accuracy, as radon levels can fluctuate based on various factors such as weather and home ventilation.

The decision to perform an additional short-term test stems from the need to validate the initial findings before taking further actions, such as deciding on mitigation strategies. This approach helps to avoid any erroneous conclusions and ensures any mitigation measures are based on reliable data.

In contrast, retesting with a long-term test is not appropriate immediately following a short-term measurement because long-term tests take several months to conduct and may unnecessarily delay addressing a potentially hazardous situation. While mitigation might eventually be necessary, it cannot be determined until further confirmation of the radon levels is obtained through the retest.