Bleaches or chemical foams must be used to clean sensitive electronic equipment that has been contaminated with chemical or biological warfare agents. But the neutralising agents can themselves damage the items being decontaminated. So Hans Hermann and colleagues at the Los Alamos National Laboratory in New Mexico have come up with a less damaging "cold flame" technique that burns off surface contaminants with highly reactive atomic oxygen. He hopes the technique could eventually decontaminate people's skin.
The atomic oxygen is formed from a mixture of helium and a small amount of ordinary oxygen gas, which is blown through a metal tube with an electrode fitted along its axis. Applying a couple of hundred volts to the electrode produces a plasma of ionised helium, and the ions split the oxygen molecules. While the helium ions are neutralised within a few micrometres of the end of the tube, the oxygen atoms stay intact long enough to be blown onto the contaminated surface about a centimetre away. There, the oxygen atoms react readily with organic compounds, breaking down nerve gases and other biowarfare agents such as anthrax spores into harmless constituents. Typical operating temperatures are around 100 ¡C and LANL says the oxygen burns up 99á99 per cent of the contaminants.
Hermann says the process is gentle enough to remove ink from paper, leaving the paper undamaged. LANL is now working on reducing the operating temperature to about 60 ¡C, below which Hermann believes they may be able to decontaminate skin and, possibly, open wounds. For battlefield use, Hermann envisages putting exposed soldiers through an oxygen "shower" to decontaminate them before medics treat them.
Author: Jeff Hecht
New Scientist issue 27th March 99
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