freighter requirements
going slightly off topic here, the 767 BCF freighters have no fire extinguishers in the lower cargo holds. They have the same method to fight fires as applied to the main deck fire. Depressurise, descend to 25000' and hope like hell it works out.
For carriage of certain lithium batteries, the recommended procedure is "land immediately", which, if you're over water means ditch the damn thing.
Lovely.
As far as for ANY fire warning, pax or freight aircraft, I'm landing as soon as possible, even if the fire warning has gone out, as there is NO WAY for me to determine if the fire is indeed extinguished or not.