So this concept was pretty cool. I saw when driving today. So we can all agree some people have bad or evil purposes for whatever they believe in. So what if the floors or walls of some these consistent places with these types of attacks.
Concept: Foam material or rapidly expanding chemical that absorbs shock blast and sends the material upward this minimizes the damage from the blast radius.
Active listeners in the ground or walls that sense for spark (so no smoking allowed or lighters or ignition devices are allowed into the center (screen for these at the entrance and exits). Ignition or flame or rapidly moving air causes the material to absorb expand and slow down the rate of the blast. Once again no background in this. But I see this idea. So have fun making it. If some lives are saved who cares who gets the credit. Peace. God, Universe, Muses, thank you. Humbler servant. JJ.