Environmentally-friendly fire extinguishers

Scientists have developed an exciting new method of putting out fires - carbon dioxide hydrate crystals.

Effectively a cross between dry-ice and water, CO₂ hydrates consist of a tiny molecular cage of water molecules filled with a pocket of CO₂.  They can be made by compressing liquid water with high pressure CO₂ and at a temperature close to -200 Celsius. Under these conditions some of the water molecules link together to form a ball-shaped structure, locking some CO₂ inside.

Seen with the naked eye they resemble a white powder and can be ground with a mortar and pestle to make a fine dust. This, Keio University, Japan researchers Takashi Hatakeyama and his colleagues have found, is very effective at putting out fires.

In a paper in Industrial and Engineering Chemistry Research the team use the hydrate crystals to extinguish burning methanol by sprinkling the crystals into the base of the flames.  The approach is effective because not only are the hydrates a source of water and CO₂, both of which are effective extinguishants, but the hydrates are also very cold and they absorb significant amounts of energy as they break apart to release their CO₂ cargo.  This means that they rob the fire of large amounts of heat, reducing the rate of vapourisation of fresh fuel and cutting the rate of ignition.

But surely, in these green-conscious times, their most attractive feature is that in quenching the same sized fire they use much less water and release far less CO₂ into the environment than using traditional water-based or dry-ice / CO₂ extinguishers.