For my department your scenario would be handled like this:
Collapse warrants a Mayday.
Being trapped warrants a Mayday.
Change in conditions could be an urgent if it will severely impact operations or safety.
For my department, if my means of egress become blocked and I need a ladder to a window in order to bail out, this warrants a MAYDAY. Once I call the MAYDAY, the OIC is expecting a LUNAR report from me and for us a LUNAR report is my Location, my Unit or Company, my Name, my Assignment, and what Resources I need.