Editor's note: There are corrections for this story at the end of it. 

Manhattan has a mind-boggling number of Irish bars—at least 85, according to Zagat—and Stephen Ceol has staked a claim in many of them.

“I’m the king of the Irish bars,” Mr. Ceol said proudly, standing by the bar at one such Gaelic-themed gastropub in midtown in the wee hours of a Wednesday night last month.

Upon arrival, the self-proclaimed king, bejeweled in Prada eyeglasses and a shiny necklace with a purple skull pendant, had received the royal treatment. Lingering patrons were told to leave, thus granting his excellency exclusive use of the premises. Later, the bartender paid him tribute, slapping a thick stack of twenties down on the counter.

Mr. Ceol, 40, isn’t an owner, manager or even some shadowy mob figure shaking down management for protection money.

He’s the exterminator.

“It’s a dirty job with social aspects,” said Mr. Ceol. “I enjoy seeing my customers.”

After chatting up the bartender, he headed downstairs, where he slipped into a pair of rubber gloves, fired up a flashlight, brandished his cockroach gel gun, and went on to recover the bodies of three dead bugs from a glue trap in the boiler room.

Otherwise, the place seemed pretty clean. “I could eat here,” he declared.

Afterward, Mr. Ceol hopped into his gleaming white Ford F-150 and sped uptown to the next restaurant on his list, a charming country-style kitchen on the Upper West Side, where properly empty mousetraps were duly rewarded with free leftover baked goods.

Hey, a gracious exterminator accepts whatever little perks he gets. Bug slayers aren’t quite celebrated the same way as chefs. There is no James Beard Award for Best Pest Control. Even the bartenders tend to get more respect. Yet, behind the scenes, these unsung heroes of the ever-volatile food-services industry play an increasingly vital role in an era when restaurant openings seem increasingly less common than restaurant closures by the city’s Health Department.

Indeed, there may never have been a better time to be a restaurant exterminator in New York City.

“Restaurateurs are deathly afraid of the Health Department,” said Mr. Ceol, who added that operators these days seem more willing to pay higher prices for enhanced extermination services, considering that even a temporary shutdown for sanitary violations can sometimes be enough to financially sink their business.

“We protect our customers’ reputations,” he said. “I have a high degree of satisfaction when we do a good job.”

From midnight until dawn, Mr. Ceol regularly makes his rounds, checking traps and spreading deadly cockroach gel throughout the cracks and crevices of the city’s culinary system, to the recurring retro sound of the “Miami Vice Theme.”

That is, the ring tone on his cell phone.

Given the late hours, the caller is usually his business partner, Scott Bregman—the entomological Rico Tubs to his Sonny Crockett—who is, meanwhile, rescuing restaurants from rodents in other parts of the city.

The dynamic duo’s 10-year-old company, Ecotect Scientific Pest Elimination Inc., is headquartered out of Mr. Ceol’s home, located, rather appropriately for a purveyor of deadly poisons, along Hemlock Drive in Sussex, N.J.

The pair also handle pest control at New Jersey restaurants, but those establishments generally don’t face the same level of “pest pressure” as the ones in Manhattan, with its underground tunnels and subways, rampant construction, piles of refuse, and people living on top of each other, all conditions conducive to vermin.

Nor do they face the same challenging regulatory climate.

In the Garden State, a mouse caught in a trap is considered a problem solved; in New York City, it’s a health-code violation, which puts the exterminator in a precarious position if a city inspector reaches the trapped critters first. You’re either part of the solution, or part of the problem, or both.

Their roster of clients includes some of the city’s trendiest, top-rated eateries, places so immaculately well kept that a guy can get down on all fours to look under the ovens and still come away without a speck of dirt. One client, Per Se, Thomas Keller’s temple of haute cuisine in the Time Warner Center, earned a perfect score on its most recent health inspection last month.

Then there are the far dirtier dives, generally newer clients, locations where even culinary adventurer Anthony Bourdain, star of the Travel Channel show No Reservations, might think twice about dining.

For a good exterminator, it can take only one night’s work to see results piling up even weeks later. “I had one client,” said Mr. Bregman, recalling his worst infestation to date. “I guess their kitchen guys were taking count. Thirty-two rats were killed—32!”

KILLING RODENTS HAS always been a big business in New York City, yet it seems especially prevalent amid the lingering aftermath of last year’s highly publicized rat infestation at a now-infamous KFC/Taco Bell in Greenwich Village. Video footage of rodents running rampant inside the since-shuttered fast-food joint ignited a media frenzy. Soon, camera crews were spying inside the storefronts of other eateries. The syndicated program Inside Edition later aired similar rodent scenes filmed at such illustrious institutions as Peter Luger and Blue Ribbon.

But it wasn’t until health inspectors shut down pricey Upper East Side dessert mecca Serendipity 3—home of the $25,000 chocolate sundae—that operators became truly paranoid, Mr. Ceol said.

No one seemed immune to the crackdown. Apparently embarrassed by the passing grade bestowed on that very same KFC/Taco Bell just days before the vermin video went viral, the Health Department continued closing restaurants left and right, every violation posted on its Web Site, every closure chronicled on the foodie blog Eater.

Even now, some 18 months after Ratgate, New York restaurateurs still aren’t feeling much relief from the regulatory heat.

“It just continually gets worse,” said Chuck Hunt, executive vice president of the New York City chapter of the New York State Restaurant Association (NYSRA). “People call me all the time complaining. … I’ve had conversations directly with the commissioner of health having to do with the way that inspections are conducted. His feeling is that the only way he can get restaurants to comply with the food-safety regulations is with a heavy hand.”

But what’s burdensome for one business can be a boon to another, and there are plenty of exterminators out there vying to work the lucrative food beat. NYSRA, for instance, at present counts at least seven different pest-control companies among its dues-paying members.

If he were purely a profiteer, Mr. Ceol joked, he could easily double his business by simply spending his days “passing out business cards” at 66 John Street, where inspector-flunked operators come to contest their violations and pay fines. “We might call them a couple of weeks later,” he said. “But we don’t bottom-feed like that.”

As profitable as it might sound, keep in mind that this is also a very fickle business.

“As a restaurant owner, you could love your exterminator for 10 years, and then one day, a customer sees a roach crawl across a wall, maybe that roach came in that morning’s delivery, and all of sudden, you hate your exterminator,” said former city health inspector Mark Nealon, now a paid adviser to restaurant operators through his S.A.F.E. Restaurant Consulting Company, based in Wantagh, N.Y.

“There are good ones and bad ones,” said Mr. Nealon. “There are guys that come in and really get on their hands and knees and get dirty and enjoy their jobs and do it the right way. Then there’s some other people that come in and without even bending their knees they spray under counters. In five minutes, they’re here and gone and you’re not quite sure what you just paid for.”

MR. CEOL AND Mr. Bregman would prefer to fall into the former category.

On the night of July 31, their company was called to a relatively new Mexican restaurant in Brooklyn, which had flunked a health inspection only weeks earlier, prompting the proprietor to switch exterminators.

Arriving on the scene that night, Mr. Bregman could understand why.

Under a stairwell in the basement, he quickly discovered a trail of tracking powder. “It’s a poison and mice run through it, it gets on their fur, they lick it off and it kills ’em,” he explained. “The label reads you gotta have it in a wall cavity—you can’t leave it out in the open like that. Between the staircase there and the prep area is only a matter of about four feet. It’s the worst-case scenario. Obviously, with the Health Department, they would shut ’em down.”

He set out a number of baitless, mechanical traps, which instead lure vermin simply by the size of their tiny entryways. “They’re naturally comfortable going into a hole,” Mr. Bregman said of his prey. “It spins them around and they can’t get out. It works great because it’s a repeater. You catch so many of them. I’ve had five live ones in there at one time.”

What happens to the captured critters? “I boil ’em and throw ’em out,” he said. “That’s what I have to do.”

By the look of things that night, Mr. Bregman might want some water boiling for his return trip in a few weeks. “Look at all the mouse droppings!” he said. “Look, there’s one right there,” he added, pointing to a small rodent crawling out from under a board in the back. “I’ll get ’em.”

Mr. Bregman quickly retrieved a glue board, whacked the tiny mouse with it, then carried the squealing, stuck critter to a nearby trash can.

Later, he plugged cracks in the floor and walls with a clear goo designed to quickly harden.

It is a substance that can also add one of the more interesting aspects of the job: the visuals.

“If I use cement, say, in an active mouse condition and mice come through that hole, they’re gonna go through wet cement. With this, if I seal up that hole and a mouse comes through, he gets stuck in it. He’s not going to be able to penetrate it.

“And I’ve had that happen,” he added. “One of my accounts has a mouse whose head is stuck in this stuff in a hole. You can barely see it because it’s thick, but if you really look close, you can actually see it.”

CORRECTION: This article has been modified to reflect a correction. The original version erroneously stated that perenially popular Union Square Cafe had been previously closed by the city Health Department; in fact, it had not been closed. The Observer regrets the error.

cshott@observer.com