Pasadena's Hot Hot Hot shop fires up its customers.

The question typical "chile-heads" ask most frequently when visiting the Hot Hot Hot shop in Old Town Pasadena for the first time: "What's the hottest you got?"

And proprietors Perry and Monica Lopez have a ready answer.

"We lead them to Pure Hell," explains Perry, a professional jazz drummer who once attended chef's school.

But heat is in the mouth of the beholder, adds Monica, a former entertainment industry professional who shares her husband's passion for things fiery. "Hot is a relative term - it varies with different people," she explains.

Pure Hell, which has a pineapple twang, is among the absolute hottest of the 200-some sauces and salsas Hot Hot Hot carries. Like other sauces high on the heat scale, Pure Hell's base chile pepper is the habanero.

On a standard 1-to-10 rating scale, the habanero rates a 10, tabasco and cayenne are eights, while the jalapeno wimps out with a five, the Lopezes explain.

But as many of the five-month-old shop's regular customers know, the difference is even more dramatic on the "Scoville" scale, which is based early 20th Century experiments conducted by Parke-Davis pharmacologist Wilbur Scoville.

In developing the scale, Scoville began by extracting capsaicin, the substance that makes chiles hot, from leading pepper varieties. He then added sweetened water in defined proportions until a mixture was barely perceptible on his tongue.

Jalapenos check in at 2,500 to 15,000 Scoville Units - habaneros range from 100,000 all the way up to 300,000.

As any visitor can plainly see and taste, hot sauce names frequently reflect the higher end of the scale. Hot Hot Hot's sample table - which occupies much of the floor space at the Lopez's small shop - features bottles and jars of selections such as Devil's Tingle, 911, Jamaica Hell Fire, Brother Bru-Bru's Spitfire Red and Hot Buns at the Beach.

In fact, container names and labels alone can create an attraction, the partners point out. The popular Ring of Fire - Monica's favorite - comes equipped with a crying towel. The Vic's Fire hot sauce bottle includes an eye dropper.

Along with heat degree and label "fun," unusual taste is a third general ingredient of hot sauce popularity, Monica notes. Various mustards, fruits - even the sweet potato - constitute the "base" of selections available at Hot Hot Hot.

The relative popularity of various sauces "runs in cycles." Perry observes after five months of operations. And those cycles have been running hot -- at sales levels nearly double the Lopezes expectations. "For a while there, we couldn't keep Lotta Hotta in stock," he recalls, elaborating that Lotta Hotta is the manufacturer of a chile-laced chocolate fudge sauce.

"It's taken us six months to track some of the sauces down," Perry continues, noting that he and Monica source sauces from Michigan to Mexico to pepper-rich Costa Rica. And of course, "we try everything before we buy it," Monica assures, adding that she and Perry found scores of selections at the Fiery Foods Show in Albuquerque.

Why do these two chile-lovers-turned-retailers search so far and wide to fill their shelves with super-spicy sauces? Because a growing segment of the population -- worldwide, apparently -- is becoming hooked on peppers.

Hot Hot Hot's mailing list already numbers some 800 addresses -- stretching from Austria to Australia. And certain repeat customers to the Pasadena shop regularly trek from San Diego and Redlands. Half of Hot Hot Hot's visitors make the trip specifically to shop for hot sauce; half stop in while touring the trendy Old Town shopping district.

"One guy comes in here every day," Monica notes.

For the regulars -- which the Lopezes dub "chile-heads" or "culinary thrill seekers" -- the main attractions are the edible adventures and reported health benefits chile peppers provide.

Like the proprietors, many regular clients cook with chile peppers and hot sauces "every day of the week," Perry explains. He and Monica note that hot sauces can be great on or in meats, fish and poultry, pastas and potatoes, vegetables, soups and salads, eggs, muffins -- even cookies, ice cream and peanut brittle.

"Like us, a lot of people see it as fun, different, adventurous," Monica says. "It also gives some people a 'buzz,' an endorphin kick -- like when you exercise," she continues.

"It can be kind of addictive, too," she cautions. "Some people build up a tolerance and need more and more peppers to get the same thrill," she continues.

And then there's the "medicinal qualities" of chile peppers, as Perry puts it. As a recent report in "Longevity" magazine notes, peppers are natural anti-oxidants full of beta-carotene and vitamin C. High levels of capsaicin are also thought to help peppers speed metabolism and reduce clotting, the "Longevity" report states.

And as most who partake of the sauces immediately realize, the concoctions are highly effective decongestants, and capsaicin is a natural expectorant, the magazine reports.

With more than 70,000 people now subscribing to "Chile Pepper" magazine, the Lopezes assert Hot Hot Hot's unexpectedly good fortune will continue. "It's not just a passing fancy," Monica insists.

She and her husband also offer some advice to neophyte customers who come in to taste sauces -- using tortilla chips or paper cups or directly from their hands -- at the Hot Hot Hot sample table. Milk, not water, kills the burn.