The new provisions came into effect January 2009. This recognised that it may be safer to load the CAO DG in the underfloor compartment where that compartment is Class C. That way the crew actually have some fire suppression, rather than just having to depressurise the aircraft and hope that the fire goes out, which is all that you have with the maindeck Class E compartment.
This was evident from long ago...with the DC-6/7 (which had positive fire suppression in their class 'C' underfloor compartments)...yes, that long ago.
Positive fire suppression is far better than..." I hope it goes out', with some of the present regulation/design criteria.
