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Vacuuming people to check for explosives and drugs is now a routine event on Capitol Hill in Washington. Capitol Police have purchased 30 state-of-the-art Itemiser detection machines from Massachusetts-based Ion Track Instruments. The devices-installed at all public entrances in the 25-block Capitol complex-are part of a new $123-million (U.S.) police security budget, up 20% from 2001. Each Itemiser costs $38,000.

- A vacuum attachment on a wand collects particles from people; belongings are either vacuumed or wiped with a swab.

- Samples are put into a "desorber," where they are heated to create vapours. Any narcotics or bomb molecules from the sample will pass through to the ionization chamber.

- Molecules react to gases circulating inside the chamber. The gases keep the molecules electrically charged, or ionized. Generally, a narcotics molecule would carry a positive charge, while a bomb molecule is negatively charged.

- An electrical field then propels the ions through a detector tube, which is connected to the electrode.

- The electrode measures how fast an ion moves through the tube-narcotic and explosive ions travel at specific speeds. This also identifies the substance, since each ion has a unique chemical signature.

- It takes four to 10 seconds for the Itemiser to analyze each sample. The results are then displayed on an LCD screen.

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