DOUGLAS HAYES WAS PRETTY CALM,

given that chimney sweep Jay Hall had just told him it would cost more than $5,000 to fix the chimney of the century-old Laurel house he had recently bought. Until the work was done, Hall went on, it would be risky to use the wood-burning fireplace in the dining room or the gas-log fireplace in the living room.

Hall wasn't wearing the chimney sweep's traditional trademark of top hat and tails when he broke the bad news (though he does keep a topper in his service van to don for the customer who insists). This thoroughly up-to-date representative of an old-fashioned trade looks more like an astronaut when he's ready to do battle with a chimney; he's swathed in a suit of impermeable Tyvek, peering through goggles and breathing through a $500 state-of- the-art respirator strapped to his back. A far cry, indeed, from the scrawny chimney-sweeping boys of Charles Dickens' London who, says Hall, often shinnied naked through the twisting flues they were cleaning so their clothing wouldn't snag and trap them.

Hall was an emergency medical technician before he joined with a fellow EMT, Mark Dziegrenuk, to found their firm, Sweeps of Laurel, five years ago. He talks of chimneys almost as if they were patients. There was a hint of sorrow in his voice at one customer's house as he pointed to a heavy creosote buildup in a chimney's throat. (Creosote is the most common disease Hall treats, an inflammable byproduct of burned wood that accumulates in chimneys and looks like black popcorn.)

The energy crisis of the mid-'70s and the subsequent revival of wood-burning stoves as a way to hold down home heating costs led to the unexpected renaissance of chimney sweeps, according to John Bittner, the executive secretary of the Olney-based National Chimney Sweep Guild.

Bittner estimates there are between 7,500 and 7,800 chimney sweeps or sweeping services across the country. The 11-year-old guild, which seeks to be the standard- maker of the trade, has formally certified 1,414 of them, including Hall.

Hall's diagnosis at the Hayes house -- severely water-damaged chimney in danger of collapse and flues needing dampers and stainless-steel lining -- had that familiar medical flavor of meticulous history-taking, probing investigative work and prescription of remedies that would restore the chimney to health. A good bedside manner doesn't hurt in the sweeping business.

"It makes me very happy to go into someone's home, see an obviously dangerous situation and do something about it," he said. "There are really a lot of unsafe chimneys out there."