THE FIRE LAB · OFFENSIVE DEFENCEYou can't put out a fire you can't reach.
A fire burning thirty centimetres underground had defeated the farmers for days. It was extinguished by injection, at a dilution of half of one per cent.
This morning we were called to a farm outside Johannesburg. A large area of horse manure had caught fire and was burning underground. The farmers had been at it for days and couldn't get it out.
If you've never dealt with one, a deep-seated fire in organic material is a different animal from a fire you can see. There's often no flame at all. It burns slowly, below the surface, at temperatures that persist for weeks. You put water on it and the water runs across the top and drains away. The fire is thirty centimetres below where your water is going.
That isn't a firefighting problem. It's a delivery problem.
So we didn't try to cover it. We went into it.
Five litres of Hydra X concentrate into a thousand-litre water tank — a dilution of half of one per cent. Then we injected that solution into the ground with a pneumatic lance, down to thirty centimetres, into the burning zone itself.
We reached the fire instead of covering it. Every litre went where the combustion actually was. Nothing ran off, because nothing was applied to a surface that sheds water.
Our normal working dilution for fuel and structural fires is six per cent. At 0.5%, one thousand-litre container of concentrate treats two hundred thousand litres of water. Over a large area, that's the difference between a logistics operation you can run and one you can't.
It didn't come back. The surface spray afterwards was housekeeping, not the intervention.
I want to be straight about what this is and isn't. It was an operational job on a live fire, not an instrumented test. Nobody was measuring. And horse manure is not peat.
But what they share is the thing that makes both so hard to extinguish: a smouldering fire in dry, porous organic material that sheds water from above.
That description covers a lot of ground. Peat bogs and moorland. Compost and mulch stockpiles. Silage. Landfill. Coal spoil. Biomass and wood chip stores. Anyone who's stood next to one of these knows the frustration — you apply water for days, the steam looks encouraging, and a week later it's still glowing.
The chemistry isn't complicated. Reduce the surface tension of water and it stops beading and starts wicking into porous material instead of running off it. Take heat out faster and the fuel drops below the temperature it needs to re-ignite, rather than the flame simply being knocked down while the fuel stays hot underneath.
That's what the concentrate does. What today added was the delivery method — and that turned out to be the missing half.
I'd like to see this tested properly, by someone other than us, on real peat, with measurements taken. If you work in wildfire, land management or waste handling and you've got a smouldering fire you can't reach, I'd like to hear from you.
