Safes - Fire Protection (Slabs?)

[Joe_G.]

I have a good safe for the items I keep at home but could use a little more room (for guns etc.) and have been looking at upgrading over the last couple years. I have not yet found a good site that compares safes against one another in a consistent fashion. Liberty likes to rate their safes as a function of time at 1200F before internal temperatures hit 350F (I believe this is average internal temperature). A Liberty Lincoln, for example, can withstand 90 minutes at 1200F before internal temperature rises to 350F (absorbing 95k BTU in the process). Champion and others rate their safes at different temperatures and test procedures making it difficult to directly compare.

In trying to pick out the right safe for my collectables I'd like to better understand what internal temperatures I need to target. For example, I know the following:

Paper will begin to yellow at 150C (302F)
Paper will auto-ignite at 218-246C (424-475F)

Cardboard would be higher, not sure about thin albumen photos mounted to cardboard.

So Liberty and others who allow up to 350F internal temperature for their safe's rating allow some paper yellowing but stop well short of when the paper auto-ignites.

Now to the point of my post . . . Does anyone know what temperature our slabs can safely withstand? Will they damage our keepsakes well before hitting 350F? Is anyone aware of tests with SGC and/or PSA slabs (or NGC/PCGS for coins)?