Nishi-ku Tonarigumi (neighborhood association) demonstrates their bokugo (little hole). They have decorated it with plants. The women in the background are wearing zukin (air-raid hood) that was intended to protect the wearer from heat and burning embers. In practice, the fire bombings were so intense, the zukin caught fire. These open-pit shelters caused accidents, as they were not well marked and the plantings hid the edge from view. Without a strong cover buried deep like the corrugated steel Anderson shelter used by the British, the open pit shelters could burn or be crushed by collapsing buildings during the fire raids. The occupants, if they survived the flames, bombs, and debris, they were asphyxiated by the lack of oxygen. Fukuoka was firebombed on June 19, 1945, by 221 B-29 Superfortresses of the 73rd and 313th Bomb Wings. 1.37 square miles (3.55 square kilometers) were burned out.