AS for the decline of children dying in fires ... there is another significant factor that occured inthe same timeline. SMOKE Detectors... and the laws requireing rental units and new construction. Most people added smake alarms once they became common place in the market and could be easily installed.
Any way .. more people die from the smoke ... not the fire!
As for being concerned enough to pretreat.... I would not add any chemicals.... any benifits ( as mentioned in earlier posts) would be washed away after a few washings.