Blast resistance is a block's ability to withstand an explosive blast. The amount of resistance depends on the block, and how big the explosion is.
The four basic physical protection strategies for buildings to resist explosive threats are:
1) Establishing a secure perimeter;
2) Mitigating debris hazards resulting form the damaged facade;
3) Preventing progressive collapse,
4) Isolating internal threats from occupied spaces
For more infomration, see ASCE 59 - Blast Protection of Buildings