When is a chair not a chair? When it's a backpack, a briefcase or condensed into a plastic package the size of an Evian bottle.

At the Paris Furniture Fair which ended here last week, young designers proved that the telephone is not the only aspect of modern life that's become mobile of late. Even chairs can travel.

French designer Francois Azambourg's "Instant Chair" was the most revolutionary. It starts as a package about the size of a six-pack. Bring one home, turn the ignition buttons, shake, and, like magic, it will unfold into a chair. The secret: a newly patented airtight textile pouch containing two liquid components and a structural network of wires. When combined, the liquids heat to boiling point, turning into a polyurethane foam, which inflates the plastic pouch and cools into a solid.

The Paris show opens the international design season each January with a five-day streak of creativity. Buyers and manufacturers race on to Germany to take in Cologne's major furniture trade show, this year Jan. 17-23. Milan's trend-setting Salone del Mobile follows in April, New York's quirkier International Contemporary Furniture Fair takes place in May, and London's 100% Design show will be in October.

As Azambourg's chair shows, the French fair is an incubator of talent at the cutting edge. One reason is VIA, the design support group that displayed the inflatable chair.

VIA is an organization particular to France in which government and industry come together to fund and manufacture contemporary design. VIA has provided a showcase for young French designers, and foreigners working in France, for 20 years.

To celebrate its anniversary, VIA has launched an expanded Web site (www.via.asso.fr) to introduce over 600 designers, either French or working in France, to the global Internet audience. The site is up in French; an English-language version is scheduled for Feb. 1. Along with photos and biographies, videos are planned to demonstrate the avant-garde designs in action.

Philippe Starck is proof that VIA proteges are not just one-day wonders. In 1982, VIA financed a collection of Starck's designs, which led to his collaboration on the Cafe Costes in Paris. The cafe chair became a design icon. (It's on display in the renovated Centre Pompidou along with a molded plastic bookcase by Gaetano Pesce, another VIA beneficiary.) Starck moved on, of course, to design a string of high-profile hotels for Ian Schrager, as well as a plethora of furniture and objects. Starck credits VIA with giving his career a 10-year jump.

A recurring theme at this year's fair was a new lifestyle emphasis on what the French call "nomadism." Don't try to pack up and go with Azambourg's inflatable chair; his process is irreversible. But Xavier Moulin's designs, also for VIA, included the multi-functional nylon and foam "Padybag" briefcase. It unfolds over a chair like a desk or can be used as a cushion. His inflatable, thermo-sealed "Poufybag" is a backpack that doubles as a stool. Moulin also showed an all-terrain lamp called the "Balladeuse," designed with Izumi Kohama. It consists of two polyurethane gel-filled pouches enclosing a light bulb, and can be worn over the shoulder, thrown over a door or draped across the back of a sofa or chair.

Brothers Ronan and Erwan Bouroullec were commissioned to produce the fair's colorful scenography. With VIA support, Erwan also showed a contemporary version of a traditional enclosed bed from his native Brittany. It consists of a raised compartment with a ladder for access. Enclosed beds provided privacy in one-room cottages; Bouroullec's could do the same in a modern loft.

Where once VIA offerings might have been more wacky than workable, the emphasis this year was on designs that could be the first model of a production line. A multi-position bed, chaise and chair by Jean-Marc Gady is one example. Called "Moods," it consists of a gray flannel-covered foam platform and an adjustable white leather cushion that slides along an integrated track. Jean-Louis Guinochet's multipurpose plastic bench comes with stackable stools that slide over the bench. The pieces could be arranged as a coffee table, chair, game table or waiting-room seating.

Israeli designer Ilan Korren blurred the barrier between carpet and table with a piece that could serve as coffee table, magazine rack or footrest. Named "Fraise" (French for a ruff collar), it is made of a nonsticky Velcro-like rug held with large hair clips. It, too, can be rolled up and carted away.

Jean Bond Rafferty writes regularly from Paris for Town & Country, Metropolitan Home, House & Garden and other design magazines. She has reported on the Paris Furniture Fair for The Washington Post since 1993.

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CAPTION: All shook up: Francois Azambourg's instant chair.

CAPTION: Form and function: Ilan Korren's bunched rug serves as coffee table or magazine rack. Above left, Moulin-Kohama's all-terrain lamp.

CAPTION: Bed in a box by Erwan Bouroullec.