Press

I explained the (3) factors associated with blasting.  Fly rock, vibration and air blast overpressure (ABOP) but my lucid, engineer speak explanation didn’t make the cut.  What people experience most is the air blast over pressure, not the vibration.  ABOP is measured in Decibels, vibration is particle velocity and is measured in Hertz.  Fly rock is controlled using mats – and is very rarely an issue.

Allowable ABOP is equivalent to a 20 mph wind gust and is caused by the compression of the surrounding air due to the expansion of the blast gases.  Vibration (particle velocity) is allowable up to speeds of 50 mm/sec.

A tell tale sign that ABOP is in excess of allowable is if glass breaks.  ABOP is limited to 133 decibels…poor quality glass breaks at about 150 Decibels.

When inside a structure, the structure type is a significant factor in how much ABOP is felt by the occupants.  That is why a person outside the structure doesn’t necessarily notice the ABOP as much.

Human perception of blast effects is unreliable