As tensions rise after U.S. strikes on Iranian nuclear sites, interest in nuclear fallout shelters has resurfaced. Two maps now show the locations of thousands of potential shelters across the U.S., many dating back to the Cold War era. However, experts warn most are no longer viable.

“These shelters were never meant to withstand the blast, just the fallout,” explained Sean Gold, Air Force veteran and founder of TruePrepper. He noted many shelters lack supplies or proper shielding. “The canned food and medical kits are likely gone or expired.”

States like New York, Texas, and Michigan still have hundreds of marked shelters, often in basements of older buildings. Yet, “lots of buildings are still marked as having fallout shelters — but not all of them are still active,” the report warns.

For protection, Gold says shelters need thick shielding (like steel or concrete), filtered ventilation, food and water for weeks, and waste disposal systems. Shelters should be located away from likely blast zones but close enough to reach quickly.

Given most Cold War-era bunkers are outdated or removed, FEMA now advises people to “shelter in place” in basements or inner rooms with thick walls during a nuclear event.