The results of a field blank test should approximate which of the following?

A field blank test is designed to assess the background levels of the measurement device and to ensure that any readings obtained from actual samples are not influenced by contamination or cross-sensitivity of the equipment. The expected outcome of a field blank test should align closely with the device’s Lower Limit of Detection (LLD).

The LLD indicates the lowest concentration of radon that the device can reliably measure. In a field blank test, results should ideally reflect this limit or be at or close to zero, demonstrating that the device is not detecting any radon due to noise or contamination from the environment. This verifies the device's sensitivity and ensures it will provide accurate measurements in real-world situations.

Therefore, the field blank test results approximating the device’s LLD is crucial for validating proper function and reliability before you begin measuring radon levels in the field.