(b) Each specific operational status is defined as follows:

1. (1) Underground mine:

   1. (i) Producing—has at least one MMU unit producing material.
   2. (ii) Nonproducing—no material is being produced.
   3. (iii) Abandoned—the work of all miners has been terminated and production activity has ceased.

2. (2) MMU:

   1. (i) Producing—producing material from a working section.
   2. (ii) Nonproducing—temporarily ceased production of material.
   3. (iii) Abandoned—permanently ceased production of material.

3. (3) DA:

   1. (i) Producing—activity is occurring.
   2. (ii) Nonproducing—activity has ceased.
   3. (iii) Abandoned—the dust generating source has been withdrawn and activity has ceased.