Also, already in WW II the "normal" bomb shelters (also mentioned in the article) weren't effective protection to the methods proudly used by the British and US war planners:

https://emedicine.medscape.com/article/833665-clinical

"Increased ambient environmental temperature from burning napalm has been known to cause the deaths of individuals in raid shelters as a result of radiant heat and dehydration. This was a frequent cause of death in the bombing raids carried out over Hamburg, Germany, during World War II."