Det cord, short for detonating cord, is a flexible tube filled with a powerful explosive that detonates along its entire length almost instantaneously. It looks similar to a thick piece of rope or clothesline, but its core contains a high-explosive powder that travels at speeds above 5,000 meters per second, fast enough to cover a football field in roughly one-fiftieth of a second. It’s used primarily in mining, demolition, and military operations to set off multiple charges at once or to cut through materials with precise timing.
What Det Cord Is Made Of
The basic structure is simple: an explosive core surrounded by protective layers. The core is a fine crystalline powder, most commonly PETN (the same explosive found in many detonators and boosters). Some cords use alternative explosives like RDX or HMX depending on the application. The explosive content is measured in grains per foot, a unit borrowed from ammunition. A light-duty cord might hold 25 grains per foot, while heavy-duty versions carry 200 grains per foot or more.
Wrapped around that explosive core are layers of woven textile, plastic jacketing, or both. These outer layers serve a few purposes: they keep moisture out, add tensile strength so the cord doesn’t snap when pulled across rough terrain, and protect the explosive from accidental friction or impact. In specialized versions, such as those used in aerospace or military settings, the layers can include fiberglass overbraid, foam polyethylene insulation, and even stainless steel braiding for extra containment.
How It Differs From a Fuse
Det cord looks a lot like a traditional safety fuse, which is a common source of confusion. A safety fuse is a hollow cord filled with a slow-burning powder similar to black powder. It burns at a controlled, visible rate, giving the user time to get to a safe distance before the charge goes off. Det cord does the opposite. It detonates, meaning the explosive reaction travels through the cord at thousands of meters per second rather than smoldering along at a few centimeters per second. There’s no visible burn, no countdown. The entire length goes off essentially at once.
This speed is the whole point. Because the detonation wave moves so fast, det cord can connect multiple explosive charges across a wide area and set them all off within microseconds of each other. A safety fuse lights one charge after a delay. Det cord synchronizes many charges simultaneously.
Detonation Velocity
The detonation velocity of modern det cord ranges from about 5,000 to nearly 8,000 meters per second, depending on the explosive type and cord construction. For context, that’s roughly 15 to 23 times the speed of sound. PETN-based cords typically sit in the 6,500 to 7,000 meters per second range. This extreme speed is what allows det cord to reliably initiate other explosives on contact. When the detonation wave hits a connected charge, the shockwave is powerful enough to trigger that charge without any additional booster.
Color Coding and Identification
Different explosive loads are identified by the color of the cord’s outer jacket. In one common system from a major manufacturer, green indicates a 25-grain-per-foot load, yellow marks a 50-grain cord, and orange signals a heavy 200-grain version. This color coding lets workers in the field quickly confirm they’re using the right product for the job without needing to read fine print. Higher grain loads produce more explosive force per length, so using the wrong cord could mean either a failed detonation or far more force than intended.
Mining and Demolition Uses
The most widespread use of det cord is in mining and quarrying. When a mining operation needs to blast rock, workers drill dozens or even hundreds of holes into the rock face, fill them with bulk explosives, and then connect all the charges with det cord running between them. A single detonator fires the cord, and the cord initiates every charge along its path. This creates a coordinated blast pattern that breaks rock efficiently and predictably.
In demolition, det cord serves a similar coordination role. It can also be wrapped around structural steel or concrete columns to cut through them directly. The explosive force concentrated along the cord’s length acts like a linear blade, slicing through material in a controlled line. Construction crews also use it for trenching, where lengths of cord are laid in a line and detonated to open shallow channels in the ground.
Military and Tactical Applications
Military forces use det cord for breaching doors, walls, and obstacles. A charge is constructed from det cord shaped to fit a specific target, whether that’s a doorframe, a padlock, or a section of wall. The cord’s flexibility makes it easy to mold against irregular surfaces, and its near-instant detonation means the breach happens before anyone on the other side can react. In tactical breaching, speed matters because a fast entry reduces the window for a violent response from anyone inside.
Det cord also sees use in explosive ordnance disposal, where technicians use it to destroy unexploded bombs or improvised devices from a safe distance. In combat engineering, it helps clear obstacles like concertina wire and wooden barriers.
How It’s Classified for Transport
Transporting det cord falls under strict hazardous materials regulations. The U.S. Department of Transportation classifies it as either a Class A explosive (the most dangerous category, now equivalent to the international UN classification 1.1D) or a Class C explosive (UN 1.4D), depending on the explosive content. Cords with more than 100 grains per foot fall into the higher hazard class. Det cord cannot be shipped in the same vehicle as detonators, detonating primers, or certain fireworks, because the combination of initiation-sensitive devices and high explosives in close proximity creates an unacceptable risk of accidental chain detonation.
What Sets It Off
Det cord requires a detonator to initiate. You can’t set it off with a match, a spark, or by hitting it with a hammer under normal conditions. The explosive core needs the intense shockwave from a blasting cap or electronic detonator to start the detonation chain. Once initiated at one end, the detonation wave self-propagates through the entire length of the cord. This relative insensitivity to accidental ignition is what makes it practical to handle, transport, and work with in the field, despite the extreme power of the explosive inside.