Incendiary/Thermal Effects

Effects based on blast pressure[1]

Potential Injury Pressure (PSI) Structural Effects
Loss of balance/temporary ear damage 0.5-3 psi Glass shatters; facade fails
Slight chance of eardrum rupture 5-6 psi Cinderblock shatters; steel structures fail; containers collapse; utility poles fail
50% chance of eardrum rupture 15 psi Structural failure of typical construction
Lung collapse/damage 30 psi Reinforced construction failure
Fatal injuries 100 + psi* Structural failure
  • Incendiary/Thermal effects are the fire and heat effects that occur in the immediate vicinity of the explosion.

Low explosives

  • Produce longer incendiary thermal effects than high explosives.

High explosive

  • Produces higher temperatures but for a shorter time.


Fragmentation occurs when pieces of the explosive device or its container come apart and are driven outward from the center of the blast. Shrapnel may be added to the device to increase the number of projectiles created by the blast. Shrapnel includes nails, marbles, ball bearings, or other materials placed in and around the device.

Blast Effects

Blast-pressure effect includes a positive-pressure phase and a negative-pressure phase.

Positive pressure

  • Moves rapidly from the point of origin of the explosion, pushing the air away from it and delivering violent force to everything in its path.

Negative pressure

A vacuum/suction phase, which accounts for much of the debris near the area of greatest damage.

Ground Shock

Ground and/or water shock is produced by the explosive shockwave being transmitted through the ground and/or water or through anything the explosive device is in contact with or buried within. If the device is in contact with a building, the shock transmits through the building walls.

Post Blast Response Hazards

Structural Hazards

Post-blast structural hazards include glass, fragment, and collapse:

  • Glass hazards include projected, falling, and static hazards.
  • Fragments include concrete, steel, and other structural components that dislodge from structures or a debris field.
  • Collapse hazards are created by the catastrophic failure of structural components resulting from the blast pressure. This, in turn, may result in the progressive collapse (i.e., pancaking) of a structure.

Other Hazards

  • Natural gas, electrical lines, and other utilities can be severed by an explosion
  • Contaminants, such as body fluids, may contain pathogensm.
  • Conventional explosives can be used to disseminate or mask dissemination of other Chemical, Biological, Radiological, or Nuclear hazards.

•Additional devices could be anywhere and may be placed specifically to target individuals. Terrorists use these additional devices to generate fear and panic.

See Also

External Links


  1. Terrorism Handbook for Operational Responders by Armando Bevalacqua and Richard Stilp (1998) and the Department of the Navy EODB 60 A-1-1-4 (2001) “Table A-1 http://www.fema.gov/pdf/plan/prevent/rms/428/fema428_ch4.pdf