This is because that TNT explosion within a distance of 3M is characterized by Shock Pressure being much superior to Dynamic Pressure.

The most accurate calculation results about TNT explosion affecting on the wall when TNT 10Kg is exploded in 1M x1M room are as follows

Here are 12 situations to consider.

◆In case of sealed condition.

①. 10 kg, sealed, explosion at the wall floor location :180bar

②. 10 kg, sealed, explosion in the middle of the wall :320bar

③. 10 kg, sealed, explosion at wall ceiling location :180bar

◆In case of opened condition.

①. 10 kg, opened, explosion at the wall floor location :180bar

②. 10 kg, opened, explosion in the middle of the wall :320 bar

③. 10 kg, opened, explosion at wall ceiling location :50 bar

◆In case of sealed condition.

①. 20 kg, sealed, explosion at the wall floor location :300 bar

②. 20 kg, sealed, explosion in the middle of the wall :530 bar

③. 20 kg, sealed, explosion at wall ceiling location :300 bar

◆In case of opened condition.

①. 20 kg, opened, explosion at the wall floor location :300 bar

②. 20 kg, opened, explosion in the middle of the wall :530 bar

③. 20 kg, opened, explosion at wall ceiling location :80 bar

Generally, the design of the blast proof door is based on the Dynamic Pressure, but it's wrong to apply the Dynamic Pressure only for the explosion within a distance of 3M.

Again, this is because that TNT explosion within a distance of 3M is characterized by Shock Pressure being much superior to Dynamic Pressure

All calculated values from opened websites like UN - SaferGuard - Kingery Bulmash Blast Parameter Calculator are only based on Dynamic Pressure.

If you want to confirm exact calculated values, it's one of options to confirm via Distribution C: Distribution authorized to U.S. Government agencies, and their contractors:; Critical Technology: Other request for this document shall be referred to U.S. DoD.