CES Explosives Safety & Handling 3 — Questions and Answers
Question 1: What is the primary purpose of a 'blasting mat' during surface blasting operations?
- To protect the blasting machine from weather
- To prevent fly-rock from projecting beyond the blast zone (Correct answer)
- To insulate electric leg wires from ground current
- To absorb excess moisture around borehole collars
Correct answer: To prevent fly-rock from projecting beyond the blast zone
Blasting mats are heavy woven steel or rubber covers placed over shot holes to suppress fly-rock and limit debris projection distance.
Question 2: Under ATF regulations, what is the maximum quantity of explosive material that may be stored in a Type 3 magazine (portable/jobsite box)?
- 25 lbs
- 50 lbs
- 100 lbs (Correct answer)
- 150 lbs
Correct answer: 100 lbs
A Type 3 portable magazine (day box) may store up to 100 pounds of explosive material when properly secured on the job site.
Question 3: Which factor most directly controls the 'critical diameter' of an explosive?
- The length of the borehole
- The minimum charge diameter needed to sustain detonation (Correct answer)
- The diameter of the blasting cap used
- The spacing between charges in a row
Correct answer: The minimum charge diameter needed to sustain detonation
Critical diameter is the minimum diameter at which a specific explosive can sustain a stable detonation wave; charges smaller than this diameter will fail to propagate.
Question 4: When an explosives vehicle is involved in a traffic accident, what is the FIRST action the driver should take if there is no fire?
- Unload the explosives immediately onto the roadside
- Warn approaching traffic and notify emergency services and the employer (Correct answer)
- Attempt to drive the vehicle away from traffic
- Transfer the explosives to a passing vehicle
Correct answer: Warn approaching traffic and notify emergency services and the employer
The driver must immediately warn other traffic, call emergency services, and notify the employer per DOT and ATF requirements without moving or unloading the cargo prematurely.
Question 5: What does the term 'VOD' (velocity of detonation) indicate about an explosive?
- The time delay between initiation and detonation
- The speed at which the detonation wave travels through the explosive column (Correct answer)
- The volume of gas produced per pound of explosive
- The distance the explosion travels before dissipating
Correct answer: The speed at which the detonation wave travels through the explosive column
VOD is the speed in feet or meters per second at which the detonation shock wave propagates through the explosive, indicating its energy release rate.
Question 6: Which action is required before stemming a borehole that contains a primed explosive column?
- Detonate all adjacent holes first
- Ensure the detonator leads are shunted and secured away from the hole collar (Correct answer)
- Connect the leg wires to the blasting machine
- Remove the cap and re-prime with a fresh detonator
Correct answer: Ensure the detonator leads are shunted and secured away from the hole collar
Shunting and securing detonator leads prevents stray current or accidental contact during the stemming process from triggering premature detonation.
Question 7: Under MSHA regulations, what is the minimum permissible distance between a blasting operation and an unprotected individual during underground mining?
- 100 feet
- 300 feet
- 500 feet (Correct answer)
- 1,000 feet
Correct answer: 500 feet
MSHA requires all persons not directly involved in the blast to be at least 500 feet from the blast site or behind adequate barricades in underground mining operations.
CES Explosives Safety & Handling 3
What is the primary purpose of a 'blasting mat' during surface blasting operations?