Okay, so imagine there's a really bad storm coming that could hurt you or make you sick. Your mom or dad might say, "Let's go to the basement to be safe!" That's kind of like a blast shelter. It's a place where people go when there's a danger outside, like from a big explosion or attack.
A blast shelter is a special room or building designed to protect people from bombs or other explosives. They're made with super strong materials like concrete or steel that can block out the shockwaves and heat from an explosion. Imagine building a really strong fort that you could hide in when bad guys come, that's kind of like a blast shelter.
Some blast shelters are underground, which means they're built under the ground like a secret hideout. Others are aboveground, like a regular building but super strong. Blast shelters sometimes have special features like air filters that keep out dangerous gases or radiation. So basically, a blast shelter is like a super strong fortress that you can hide in to stay safe from danger!