RFI stands for Radio Frequency Interference.  The ASIV was originally designed to detect the presence of RF within the Alco-Sensor IV’s shielded case and send a signal to the instrument’s processor to abort the test and flag it as an RFI void.  Physical testing has since shown the instrument to be insensitive to commonly encountered RF levels.   It is not necessary to conduct an accuracy check after an RFI void – simply move away from the source of the RF, or turn off the source and conduct another test.