This happened at Willow Grove Naval Air Station when I worked there. It only took about 45 seconds to a minute to create all that foam. When they go to put out aircraft fires they don't fool around hehehe.
Now that we are on a fire subject let me show you a video. Here it is http://www.usfa.dhs.gov/downloads/media/tree_fire.mpeg
You will notice at the end of the video that the whole room goes black and it appears that there are flashes of flame through the smoke. This condition is what we call in the fire business a flashover. Notice it is at 45 seconds. If you were in this house when a flashover occured you would be lucky to survive with the protection of firefighter gear and airpack let alone your skivvies. Just some important fire safety tips. Be safe.