Final answer:
Office blanks, or controls, are necessary when using passive devices such as activated charcoal or alpha track detectors to ensure accurate radon testing. The frequency of using them depends on testing protocols, but generally at least one blank is used with each batch of detectors. These blanks provide quality control to account for potential contaminants and validate the testing process.
Step-by-step explanation:
When using passive devices such as activated charcoal or alpha track detectors for radon or similar testing, it is essential to include office blanks—also known as controls or blanks—in the sampling process. These blanks are used to account for any potential contaminants that could affect the test results, such as those that could come from the device itself or from the environment where the devices are stored prior to use.
The frequency of using office blanks depends on the protocol specified by the testing company or regulatory guidelines. Typically, for every set of devices deployed, at least one control should be included. If the testing period is extended or if many devices are used, additional controls at regular intervals may be needed. The data from these blanks are used to make adjustments to the readings obtained from the testing devices, ensuring that the results are accurate and reliable. An example of a passive device employing a radioactive element is an ionization-type smoke detector, which uses Americium-241, an alpha emitter with a long half-life, to detect smoke and trigger an alarm.
In contrast, when alpha track detectors or activated charcoal are used to measure indoor air contaminants like radon, office blanks serve as a quality control measure to validate the test conditions and the absence of contaminants that could skew the results. In summary, office blanks are a necessary component in environmental sampling to maintain the integrity of the tests, and their usage must be planned accordingly to coincide with every test series or as frequently as guidelines suggest.