It’s a profession that few people realize exists—until tragedy strikes, and suddenly they have to deal with the unimaginable. That’s when they call a select group of iron-stomached, steel-nerved workers known as trauma scene restoration specialists, biohazard remediation technicians, or simply crime scene cleaners.

Until a few decades ago, the task of cleaning up after a loved one died fell to family and friends, potentially adding trauma on top of an already terrible event. In the 1990s, a small group of companies and entrepreneurs sprang up to tackle the problem, specializing in the removal of blood, fluids, human tissue, and hazardous substances. By 2012 (the last year for which reliable data is available), crime scene cleanup was a $350-million industry in the United States, and included more than 500 companies. Here’s what these hazmat-suited heroes want the world to know about their work.

1. THEY AREN'T LIMITED TO CRIME SCENES.

The phrase crime scene cleanup brings to mind police tape and furrow-browed detectives. In reality, only a fraction of the calls these companies receive—which can come from family members, property managers, hotel owners, or anyone with a dead body on their property—are the result of a major crime. Unattended natural death (i.e., a person who dies alone and isn’t discovered quickly) and suicide are the most common scenarios. Glenn Cox, general manager at Southern Bio-Recovery, which has four locations in the Southeast, says that only about 30 percent of the 60 to 100 death scenes his company handles every year are homicides.

To pay the bills, it's common for companies to supplement with other kinds of biohazard removal, whether that's removing tear gas from a property after it's been used by law enforcement or getting rid of meth labs. Cox says that Southern Bio-Recovery also cleans up hoarding situations and decontaminates homes after viral or bacterial incidents—think MRSA or hepatitis outbreaks.

2. MANY OF THEM ARE EX-MILITARY OR LAW ENFORCEMENT.

Former Marine John Krusenstjerna founded Des Moines-based Iowa CTS Cleaners after serving two tours in Iraq. “Just experiencing things out there left me kind of wondering what happened in these situations back in the United States, who takes care of it,” he tells Mental Floss. Peruse executive bios of many trauma restoration company websites and you’ll find similar military, law enforcement, or paramedic backgrounds. Exposure to death—and the chaos it wreaks on family members—also provides valuable experience in the emotional and physical challenges inherent in cleanup. "Being able to compartmentalize in your mind, to stay focused on the task, to have integrity … all of those are attributes I believe I learned from being a soldier," Cox explains.

3. THEIR TRAINING MIGHT INVOLVE PIG BLOOD.

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The certification requirements for crime scene cleaners range from nonexistent to uneven, so most training happens in-house. James Michel, CEO at Bio Recovery—which has 22 branches around the country—says all of his company's employees are taken to a special training facility at their headquarters in New York state. "We stage crime scenes there using organic and non-organic types of fake blood: stage blood, pig blood, all different types. We recreate crime scenes with sheet rock, toilets, tile, and [trainees are] able to break it down. We have decontamination stations that are permanently set up so they can walk in and out of and really grasp how to do this on a day-to-day basis." All in all, Michel says, four weeks of such training are required before their techs are even let out on a crime site.

4. THE DEATH SCENE CAN SPREAD BEYOND THE BODY.

“All of our scenes are chaotic, and there's multiple things to do,” says Nate Berg, founder and president of Scene Clean, based in Osseo, Minnesota. “For example, in a decomposition [when a body has been left undiscovered for a long period], you've got strong odors and you've got all their personal property, which now have absorbed the strong odors.” The work becomes a matter of peeling the layers of contamination—bedding and linens, furniture, carpeting, floorboards, subfloor or sheetrock. And what’s visible to the eye (say, a small bloodstain on a carpet) may actually indicate a large pool underneath.

“A bad day is when we get called to a really bad decomposition or unattended death,” Krusenstjerna says, “and find out they’ve not only decomposed in a kitchen or bathroom but it’s dripping into the basement. We had an apartment building where it went from the third floor to the first floor.”

5. THEIR CLEANING SUPPLIES ARE NEXT-LEVEL.

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As you might expect, cleaning up the blood, fluids, and tissue left in the wake of a violent death or long-undiscovered decomposition takes more than bleach and elbow grease. The first step is detection of every spot, splatter, or shard. “We use an indicator similar to hydrogen peroxide, but it’s a much, much stronger version,” Cox says. “When it [comes into] contact with bodily fluids, it foams up and turns a very bright white color. It’s also a very strong disinfectant.”

When dealing with brain matter—which tends to harden to a cement-like consistency—Berg prefers to use an enzyme cleaner that, when absorbed by the tissue, softens it just enough to allow it to be removed with a scraper. For stubborn brain tissue, or fluid that’s seeped into the cracks between floorboards, it might be time to break out the demolition tools: crowbars, weighted hammers, circular saws. It’s also not uncommon for techs to have to dismantle furniture, remove sheetrock, or rip up flooring to get at the contaminants that have seeped in or gotten stuck.

6. THEY CAN MITIGATE THE SMELL ... SORT OF.

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There’s nothing like the smell of death. And while some techs get used to the odor, “when a body’s been there for 60 days, in moist air, you walk in and breathe that smell, and you just go, ‘This is going to be a long day,’” Michel says. Every technician wears personal protective equipment (a.k.a. PPE; think lined suits, booties, layers of gloves and respirators) to guard against blood- and air-borne pathogens, but it can be hard to avoid a quick waft now and then. “I don’t care how good you are,” Michel says, “when you twist your head in a certain way and break that [respirator] seal, that smell is coming in the mask.” To cope, and to deodorize the home, techs employ HEPA filters, air scrubbers, ozone machines, and hydroxyl generators—which use concentrated UV light to target and destroy pollutants.

7. THEY HATE SEEING CATS ON-SITE.

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That's because cats could mean cat pee. “Cat pee is my fricking nemesis,” Berg says. “Most of the time we have to pull up floors or walls and make physical contact with the cat urine because it crystallizes.” Michel agrees: “When you leave a dog by himself and they [defecate] or urinate, you can clean that for the most part. Cat spray is the hardest odor to remove.”

8. THE TURNOVER RATE IS PRETTY HIGH.

Even the toughest clean-up doesn’t compare to the emotional stress of working with grieving families or glimpsing the violence people inflict upon each other. "We only go to the worst of the worst," Michel explains. He's seen professionals in his office and around the industry turn over at a rapid rate. “We’ve had hundreds of employees come in and out of these doors throughout the years and the psychological toll is extremely difficult. Some of the tough cases, where there’s children involved, there’s a somberness in the office for days.” He says that most employees, and even owners, only last about five or 10 years, max.

9. TECHS OFTEN FUNCTION AS COUNSELORS ...

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Because everyone deals with grief differently, a crime scene cleanup tech has to be prepared for every kind of human interaction. Usually, it’s the owner or senior tech who deals with loved ones, and that might mean listening to detailed accounts of the deceased or protecting customers from seeing the worst. “Customers tend to want to tell us the whole story, starting two months back,” Cox says. “They need to vent. I have to talk with them, and sometimes I have to give them a hug and let them know that we’re here to help. We understand their situation and let them know that time heals. This is part of the healing process as well.”

10. ... BUT THEY SOMETIMES NEED HELP THEMSELVES.

Experienced techs and owners talk about the importance of separating their work and home lives. Still, not everyone is gifted with the ability to disengage (and even those who can may find the toll adds up over time). Several of the people we spoke to said their companies provide paid counseling for techs on a confidential, request-by-request basis. "All they have to do is submit a request. We take care of everything," Michel notes.

11. THEY MIGHT BLAST THE RADIO—OR WORK AS QUIETLY AS POSSIBLE.

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Techs have to find a way to work amid all that emotion. While on site, that might mean keeping things light among themselves. “We have radios in our truck,” Krusenstjerna says. “We bring the radio in the house, to help break up the time. We’ll talk amongst each other, joking about what we saw on TV the night before or what’s funny on Facebook. But the last thing we want, and where we draw the line, is if the family is in the house. Not to sound like we’re gross or gruesome but we’re not going to say, ‘Grab the tooth off the window ledge,’ because we don’t know if they’re sitting there with their ear to the bedroom door. So we’ll be quiet, and use body language and signs and stuff like that.”

12. A CLEAN-UP CAN COST $10,000.

Based on region, type of cleanup, and number of techs, the cost to customers varies wildly, from around $1000 to over $10,000. Generally, the more dispersed the fluids and tissue in the home, or the longer the decomp, the more manpower it will take and the longer the job will be—leading to higher costs. (While insurance and victim compensation will cover some of the cost, at least part of the bill still falls to the customers.) Depending on the number and type of jobs undertaken, owners of crime scene cleanup companies can clear hundreds of thousands of dollars, if not more, in profit every year. Techs themselves can make anywhere from $25 per hour to over $100 per hour. According to the Bureau of Labor Statistics, the median annual compensation for a hazardous materials removal worker hovers around $41,500, but the top 10 percent earn more than $75,000.

13. THE FACT THAT THEY'RE HELPING PEOPLE MAKES IT WORTHWHILE.

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If there was a common thread in all the conversations we conducted with crime scene cleaners, it was the immense satisfaction they take from their jobs. Despite the smells, the gore, and the grief, these individuals find great reward in the help they’re able to provide to others in their hour of darkness. “When I have a family member who’s just lost a loved one give me that hug—because they could not have done this for themselves—there is no greater satisfaction in my life,” Michel says. “If I were to die tomorrow, that would be one of the greatest things I've ever been a part of. You can't describe in words. The only way I can say is, it's the beat of another human being's heart against yours, thanking you for helping them on the worst day of their lives."