MSHA Explosives and Blasting 3

Question 1

Under MSHA regulations for underground mines, what must be done with all electrical power in an area before blasting begins?

Accepted Answer

Power must be de-energized and locked out in the blast area to prevent stray currents from triggering electric detonators

Answer

Power must be reduced to 50% capacity

Answer

Power must only be shut off to ventilation fans

Answer

No power shutdown is required if shielded detonators are used

Question 2

How long must miners wait after a blast before re-entering an area in an underground coal mine, according to MSHA standards?

Accepted Answer

At least 30 minutes, or until the ventilating current has cleared the smoke and fumes

Answer

At least 5 minutes

Answer

At least 1 hour

Answer

Until the foreman personally inspects the area with no time minimum

Question 3

Which MSHA standard prohibits the use of non-permissible explosives in the working section of an underground gassy coal mine?

Accepted Answer

30 CFR Part 75 Subpart N

Answer

30 CFR Part 50

Answer

30 CFR Part 46

Answer

30 CFR Part 100

Question 4

What is the purpose of a 'delay detonator' in a multi-hole blast pattern?

Accepted Answer

To fire individual holes in a timed sequence, reducing ground vibration and improving rock fragmentation

Answer

To allow the blaster time to reach a safe distance before any holes fire

Answer

To detonate holes only when triggered by a radio signal

Answer

To prevent detonation if the temperature exceeds a safe threshold

Question 5

Under MSHA rules, who is responsible for conducting a pre-blast inspection to ensure the blast area is clear of personnel?

Accepted Answer

The certified blaster in charge of the blast

Answer

The mine operator's safety officer only

Answer

Any miner assigned by the foreman

Answer

The MSHA inspector present on site

Question 6

What does MSHA require regarding the record-keeping of blasting operations?

Accepted Answer

Blasting records including the quantity and type of explosives used must be kept and made available to MSHA inspectors

Answer

Records are only required for blasts that cause property damage

Answer

Only the mine manager needs to keep mental notes of blasting activities

Answer

Records must be submitted to MSHA within 24 hours of each blast

Question 7

According to MSHA regulations, which of the following conditions requires that blasting operations be suspended immediately?

Accepted Answer

An approaching electrical storm or lightning

Answer

Temperatures exceed 90°F at the surface

Answer

The shift change is within 2 hours

Answer

The blast zone is more than 500 feet from the nearest occupied building