Explosive Fuse Detonation Time Calculator

Safety fuse burn time

A standard safety fuse (the Bickford type) burns at a nominal rate of about 1 cm/s (≈ 30 s per foot). Manufacturers spec it somewhere in the 0.8-1.3 cm/s range, depending on the product. Working out the delay is just t = length / burn rate. Take a 30 cm length at 1 cm/s and you get 30 seconds before detonation. On a real job you test each lot first by burning a measured piece, then pad the result with a safety margin, since humidity, age, splices and ambient temperature all shift the rate. These days a lot of operations have moved away from pyrotechnic fuse toward electronic detonators (eDev), which hit their delays with millisecond precision.

Applications

You'll find it in mining and quarry blasting (Vale, regulated by Brazil's ANM — Agência Nacional de Mineração), civil demolition (Loizos Group, Controlled Demolition Inc.), trenching and rock excavation, fireworks pyrotechnics, mining engineering courses, and military combat-engineer training.

FAQ

Is 1 cm/s safe to assume? No. Always test-burn a sample from the actual lot. Old, damp or badly stored fuse can run faster, run slower, or skip a section entirely.

What is the difference between safety fuse and detonating cord? Safety fuse burns slowly (cm/s) so the operator has time to retreat. Detonating cord ("cordtex") goes off at ~7000 m/s and links charges instantly.

Why use electronic detonators? You can program the delays down to the millisecond, vibration and overbreak drop, fragmentation improves, and the guesswork of pyrotechnic fuse goes away.