Disasters Narrowly Avoided Quiz

Answer: To release dangerous overpressure. A safety valve opens above a set pressure to prevent a tank or boiler from being dangerously overpressurized.

Answer: To reduce omissions during critical actions. Checklists structure essential checks when workload, stress or routine could otherwise cause omissions.

Answer: Because an open door no longer compartments effectively. A fire door only works as a barrier when it closes the opening it protects; wedging it open defeats much of its purpose.

Answer: Smoke and dangerous gases can spread very early. Smoke and toxic gases can spread before flames are obvious, so early warning provides precious evacuation time.

Answer: A small extinguisher is limited and smoke can become deadly. A portable extinguisher is for a manageable incipient fire; if heat, flames or smoke grow, personal evacuation takes priority.

Answer: The lunar module. The lunar module Aquarius provided shelter, power and life-support resources during much of the return to Earth.

Answer: Sunlight reflected by clouds. A rare alignment of satellites, sunlight and high clouds was misread as missile launches.

Answer: So a rupture tends to stop the train. A pressure drop commands braking, so a broken brake pipe or separated cars tend to stop rather than run without brakes.

Answer: To grip the guide rails in an overspeed. The safety gear, usually triggered by an overspeed governor, can grip the guide rails and stop the car.

Answer: Decay heat from radioactive fission products. Radioactive fission products continue to decay after shutdown and release declining but significant heat that must be removed.