In 1956, a National Personnel Records Center (NPRC) building was constructed in St Louis to hold military personnel records. The upper floor of this building caught fire on July 12th 1973. After a 22 hour fire the roof of the structure (made of prestressed concrete) suffered a 30% collapse. Ultimately the upper floor was removed post-fire. Today the building stands but remains vacant while its future fate is decided. To meet storage standards, the NPRC has since moved to a new building in 2011. While this presents an interesting historical case study from a structural fire point of view, from a purely forensics point of view there is an equally interesting case study that is still on going over 41 years to this day.
During the fire approximately 1/3rd of the over 50 million records stored were destroyed. However, some records (though badly damaged from fire and water) were salvaged (about 6.5 million). Because these records have importance for federal entitlements (for example medical and education) as well as genealogy and historical research, there is a clear need to salvage information from them. To date the National Archives and Records Administration (NARA) Preservation lab (Saint Louis Preservation Division) works to recover information from these burnt records . And I find their forensic efforts a fascinating use of available technology.
The Preservation Lab, currently experiments with infrared filters on cameras. The burnt ink shows up differently against a burnt paper backdrop because ink burns differently than paper does. Infra-red filters are used to create a contrast between the ink and paper, and with simple graphics software like Photoshop the image can be manipulated to help show what the naked eye can not. Of course the lab investigates other methods of information recovery such as new technologies (ie. sub-fibre scanning) or more detective style recovery (tracing requested records through other means). They also deal with methods for restoring the damaged documents and digitization. You can find more information on their efforts here.
This forensic effort reminds us of yet another case study of a fire where effects are not just realized immediately after, but even decades later. I encourage all readers to look into the efforts by this group when they have the time, its quite interesting work they are doing.