Depressurized when LOWER cargo fire?

[kuobin]

Hello gentlemans:
Boeing QRH want us to change landing altitude to 8000-8500 ft after lower cargo fire extinguisher discharged if we have a fire warning .Is there any reason behind? thanks.
.

[SMOC]

I take it you have a extinguisher system, it's probably to do with controlling the flow rate in the lower cargo, as you don't want to pump all the agent out of the A/C so the QRH has you set up as low a differential pressure as possible.

[ray cosmic]

Or to feed the fire/remains of it as less Oxygen as possible?

[mgTF]

or making a reverse flow of smoke/halon in the cabin