Fume: Why the Cloud Turns Orange, and What Puts It There

You know the one. Yellow smoke changing to bright orange, hanging down in the pit or over the shot after it fires.

That color is nitrogen oxide, and it means the explosive fired at low-order.

Standard ANFO burns somewhere around 12,000 to 16,000 fps. A low-order detonation could be anywhere below that.

At that speed the chemistry doesn't complete. Instead of releasing inert nitrogen gas, which is the goal, the reaction puts out nitrogen oxides. That's the visible orange cloud.

1. Water contamination. By far the most common cause, roughly 99% of fume events. ANFO absorbs moisture very quickly, and water in the hole or in storage reduces or destroys its detonation chemistry.
2. A manufacturing defect in the ANFO. Uncommon, but it can happen.
3. Wrong fuel-to-AN ratio. If you mix too much, or not enough fuel, Anfo doesn't burn right.
4. Sleeping too long. 
    - Dry ground: a theory that says the ground absorbs the fuel out of the AN like a sponge and throws the ratio off. This one is unproven and mostly a Western US observation, but if it holds, lining the holes would mitigate it.
    - Damp ground: No physical water present in the hole, but if it sleeps a long time in damp enough conditions, Anfo can begin to absorb moisture from the surrounding ground and break down.

If the hole is wet, or might get wet, line it. A liner physically separates the explosive from groundwater.

BLASTSHIELD Plus - Holes up to 6" (150 mm) is the one for small diameter holes. With carbon fiber strips through the material to prevent static buildup, and this helps it easily open at depth. It's gussets make the packaged width smaller than the hole diameter which prevents twisting on the way down.

Blastshield - Holes 8" - 14" (203 mm - 350 mm) is best for larger diameter or deep holes and has been proven to 220 ft (67 m). Just like Blastshield Plus, Blastshield is designed with carbon strips to prevent static build up, and is gusseted so that the packaged width is smaller than the hole diameter. This helps the liner install easier and reduces twisting.

Lay Flat Liner is an economical liner that works best in shallower holes <80 ft (24 m). It builds more static during installation, can stick to itself on deployment, and twists more easily, so it's may be the choice where depth isn't the challenge.

Load emulsion. It's waterproof by design.

Gas emulsion carries virtually zero fume risk. Sensitized emulsion is slightly higher, but still dramatically better than contaminated ANFO. Whenever water is unavoidable, emulsion is the safer choice.

Dewater, line, then load ANFO. It's the cheapest bulk you can put in the ground, and once the water is out and the liner is in, it performs to spec without the fume risk.

Australian fume regulations are stricter than ours, and almost every Australian coal mine lines holes as standard practice. The regulation forced the habit, and the habit works.

A coal operation in the Powder River Basin was dealing with fume events serious enough to cause blast-design restrictions and throw shot times into limbo due to wind direction.

Lining the holes eliminated 100% of fume events in lined cast and overburden blasts. The design restrictions were lifted, shot times returned to normal, and the site was able to switch from heavy emulsion to ANFO.

Almost every orange cloud starts as water getting to the explosive. Know which of your holes are wet, line the ones that are, and pick your liner based on hole diameter and depth.

Not sure which fits your holes Call us at 606-663-4069.