No other human-made catastrophes can wreak more destruction than a nuclear bomb. And it is believed that bomb shelters and bunkers can protect us.

The truth is that these structures' ability to shield people from the potent heat and blast of a nuclear bomb varies, reports Live Science.

"It all depends on where the bunker is and the quality of the bomb," Norman Kleiman, an associate professor of environmental health sciences and director of the Radiation Safety Officer Training course at Columbia University's Mailman School of Public Health, told Live Science.

"If you are 600 miles [1,000 km] away from a thermonuclear device, maybe a shelter would help you," Kleiman said. "But if you're anywhere within that blast radius, the blast, the heat, the explosion—those are going to take you out."

And then there's the question of radiation, which is the emission of waves and particles in the wake of the blast. Kleiman said it's possible to build a bunker to protect you from radiation. The walls must be lined with 3 to 5 feet (0.9 to 1.5 meters) of concrete and steel, as well as lead. This lead is embedded in the shelter's walls and doorways, so an intact bunker poses little risk of exposure to its occupants.

Peter Caracappa, executive director of the radiation safety program at Columbia University, broke down a shelter's protection ability into three components: It must be effective as a structure to withstand an explosion and weather radiation (which, in part, depends on where it is relative to the explosion), how much material is between you and the radiation the explosion emits, and how well it can keep out fallout material, or the material that's generated and released in a nuclear explosion.

Lethal radiation persists for days after the explosion, so if you were to survive the initial blast, you would have to stay in the bunker to avoid radioactive fallout.

Kleiman noted that cancer is one huge long-term risk of radiation exposure, but that and other consequences may not emerge for decades.

So, while a bunker only a few miles from an explosion wouldn't be very helpful, a good shelter dozens of miles from a blast could protect inhabitants from radiation for days.