After North Korea threatened to launch an "enveloping strike" at Guam, the territory's office of civil defence posted emergency guidelines on Friday, explaining what citizens should do in the event of a missile attack. ("Do not look at the flash or fireball -- It can blind you. Take cover behind anything that might offer protection.") The advisory followed a week of alarming statements by US President Trump and North Korea, fuelling talk of nuclear apocalypse that's been good for one specific industry: Bomb shelter manufacturers.