The reality is, there is no official list. Each company needs do decide what is appropriate for their work environment.
If your are using the 'task tables' in NFPA70E, then there is a list of PPE based on hazard risk categories. Many companies take the data from a study and work the lookup table backwards as their means of adopting the 70E clothing tables.
NFPA70E does not address voltages below 50V. It appears they have gone out of their way, in particular, to ignore 24V and less.
