In 2018, a quarry in New Brunswick experienced a series of misfires. Investigation revealed the ANFO mixture was oxygen-deficient, producing dangerous carbon monoxide instead of CO2. Understanding explosive chemistry could have prevented this incident.
What is an Explosive?
An explosive is a chemical compound or mixture that undergoes very rapid decomposition when initiated by energy (heat, impact, friction, or shock). This decomposition produces:
These hot gases create extremely high pressures within the borehole, fragmenting the rock.
High Explosives vs Low Explosives
The classification depends on reaction speed:
High explosives detonate - the reaction propagates supersonically through the material. Low explosives deflagrate - they burn rapidly but subsonically.
Oxygen Balance is Critical
Oxygen Balance
Zero oxygen balance is the ideal point where:
At zero oxygen balance, products are: H2O, CO2, and N2
ANFO Example:
Employers must ensure that explosives are mixed according to manufacturer specifications to prevent toxic fume generation.
Key Takeaways
- 1Explosives decompose rapidly producing gases and heat - this creates the pressure that fragments rock
- 2Zero oxygen balance maximizes energy and minimizes toxic fumes (CO, NOx)
- 3ANFO (94.5% AN, 5.5% FO) is the standard baseline for explosive energy comparisons