Burning speed of a safety fuse is approximately which of the following?

• A. 60 seconds per yard
• B. 60 seconds per foot
• C. 80 seconds per yard
• D. 120 seconds per yard or 40 seconds per foot

Answer: (D)

Burn rate is the time it takes for a length of safety fuse to burn. For typical blasting practice, a safety fuse burns about 40 seconds per foot, which equates to about 120 seconds per yard. That’s why the correct choice matches 120 seconds per yard or 40 seconds per foot. The other rates don’t align with the common fuse performance: 60 seconds per yard would be about 20 seconds per foot, which is slower than standard expectations; 60 seconds per foot would be unusually slow and not typical; 80 seconds per yard works out to roughly 26.7 seconds per foot, also not the standard. In practice, this burn rate lets you estimate timing along a fuse line, keeping in mind that exact times can vary slightly with fuse type and conditions.