When US EPA conversion is Applied as a conversion on the PurpleAir Map, for all Indoor sensors (only Indoor sensors), which have a correct non-converted reading of 0, the US EPA conversion code does a wrong calculation for Indoor and will incorrectly display as grey/NULL in the Sensor value circle of the PurpleAir Map.
See image before US EPA conversion for Indoor sensor reading 0 without conversion:
See image after US EPA conversion for Indoor sensor reading 0 without conversion::
Please fix your Indoor conversion calculation for the US EPA conversion to read 0 instead of NULL (grey) for all Indoor sensors (Outdoor conversion calculation is correct. Only Indoor conversion for US EPA has the problem).
See also Video of the same: