The Swinging Door, in San Mateo, is holding their annual Habanero Challenge, where both the individual and company that devours the most XXX burgers will win.

“Prepare for death,” Buck Buckner warns the stranger sitting on a stool to his left.

“Twice,” adds his friend, Tom Van with a chuckle.

These two gentlemen are regulars at The Swingin Door, a popular and historic English style pub located at 106 E. 25th Ave. And no, they were not agitatedly threatening a newcomer to their bar over a game of darts or an argument over a piece of obscure sports trivia. There were no debates over politics, religion or who should start as quarterback for the 49ers.

They weren’t mad at me at all. They were trying to save me.

What had them so concerned, or perhaps more likely bemused, was the smoky object on my plate, the pub’s famous “XXX burger” that chef Bruce Johnson, the amiable but imposing looking fellow who has manned the grill and the fryer here for almost 25 years, had just prepared for me. The XXX burger compares to a habanero burger the way Angelina Jolie compares to your basic pinup run-of-the-mill superstar actress — it’s just as beautiful to stare at, but at least three times more dangerous.

“I like that I cannot get in trouble. People know they’re asking to be in pain,” admits Johnson cheerfully, estimating that he’s cooked up somewhere north of 100,000 habanero burgers in his distinguished career.

He’ll be adding to that total, considerably so, in the next 20 days as all month long The Swingin Door is holding their annual Habanero Challenge, where both the individual and company that devours the most XXX burgers will be honored, with a $50 gift certificate going to the former and a big shiny silver trophy to the latter. Last year, Informatica captured the company honor, with 65 of their employees managing to finish their burgers.

“They brought over an entire engineering department,” said owner Warren Chapman, explaining that the contest isn’t just about the trophy. “It’s also about bragging rights. Companies use it as an initiation for new employees.”

“The difference between a regular habanero burger and our XXX is the intensity of the spiciness. We use three times the peppers,” said Chapman, revealing that they use Red Savina peppers, commonly believed to be the hottest habaneros in existence. With pepper spiciness measured in Scoville Units, after William Scoville, a Detroit pharmacologist who thought to give a ratings system to such a thing back in 1912, the Red Savina checks in at 577,000 Scoville Units, according to The Chile Encyclopedia.

“It held Guinness World Records as the world’s hottest pepper, but got beat recently by a pepper from Bangladesh,” said Chapman, confirming that he is indeed in the process of tracking down the new champion for next year’s sauce.

It would be a mistake to characterize The Swingin Door as a gimmick joint, however. The pub, which was known as The Prince of Wales between 1972 and 2007 before Chapman bought the place and restored the original name, has been a San Mateo institution since 1955. Because of its close proximity to Bay Meadows, many local celebrities have set foot in here including Betty Grable, Bing Crosby and The Kingston Trio. Ronald Reagan, trying to win over potential voters, bought the bar a round when he visited in 1964.

“Famous people stopped here because they owned horses racing at Bay Meadows or knew the owners of the horses,” said Chapman.

While the rich and famous don’t show up very often anymore, the bar now draws its customers on merit. Meanwhile Chapman is effusive in his praise for Johnson, calling him the “number one fish & chips chef in the country.”

In addition, the same voters declared them “the best lunch deal” in the city for their daily $4.59 specials where there is often a line of people waiting to enter for a cheeseburger and fries or the fish & chips for what amounts to basically half of the regular menu price. The bar also features six HD TVs, (of course they have the NFL Sunday Ticket package) dueling piano contests, and a private room upstairs that’s free of charge for groups of 15 or more. It’s a scene for partyers, young and old.

My experience however, wasn’t about the good times, the drink specials, the French fries served with house ketchup made daily or the award winning fish & chips made with Johnson’s secret batter recipe. It was all about the XXX burger, a one-third pound meat patty covered in a glowing volcanic red sauce that Chapman was emphatic in pointing out could also be used on chicken or veggie burgers. To better prepare some for the experience, they give out a “firecracker,” a saltine with a dollop of the sauce.

It would’ve been easier to digest an actual firecracker.

When the actual burger is served, the bartender on duty rings a bell and all the regulars yell, “It’s habanero time,” knowing what’s in store for newbies.

“Whenever someone orders one, we watch, it’s a spectacle, an event for us. You see people sweating all the time,” explains Brian Boettcher, another regular who divulged that often watching people eat the burgers is more entertaining than whatever’s on the TVs. Johnson advises to eat the burger as fast as possible and Chapman is already holding dessert.

“We sell a lot of ice cream sandwiches, to neutralize the intense heat,” he says.