Which unit is used to express the burn rate of detonating cord?

• A. meters per second
• B. feet per second
• C. kilometers per hour
• D. miles per hour

Answer: (B)

Detonating cord burn rate describes how quickly ignition travels along the length of the cord. In blasting practice this propagation is expressed as distance per time, and the conventional unit is feet per second because field measurements use feet and timing is calculated by dividing the length by the burn rate to set delays. Using meters per second is possible in metric contexts, but the U.S. standard is feet per second, and miles or kilometers per hour are meant for vehicle speeds, not the rapid propagation of ignition along a cord. For example, if the burn rate is about 8,000 feet per second, a 60-foot length would take roughly 0.0075 seconds to ignite.