In some instances, it may not be possible to determine the date of Fgas compliance, either by lack of evidence or lack of compliance.
The AIRS software will accept Not Applicable or Not Provided into the date field, but these phrased must be pasted in, not typed:
Type the text into the System Descripton box, highlight it, press CTRL+C to copy, go to the Compliant Date box, and press CTRL+V to paste.