Transcript for Bedbug-Sniffing Dogs Might Not Accurately Detect Infestations
Now for a different kind of murder for hire, hiring an exterminator to get rid of bed did bugs in this case the exterminator has four legs, canines, usually beagles, what's the truth about those bed bug-sniffing dogs. Paula Faris put up some hidden cameras to find out. Reporter: Did you travel for the holidays? Maybe you saw your bestie in Baltimore, grandma in Grand Rapids, or were vacationing in Venice. Regardless, you were in someone else's room, sleeping in someone else's bed. Unbeknownst to you, you might have picked up the world's nastiest hitchhiker -- cimex lectularius -- the dreaded bedbug. If they weren't in your house before, well, they might be now. Bedbugs are back. You don't want to mess around with this. You only need to sit in a chair that's got bedbugs for 20 minutes and they'll be on you. Reporter: As the owner of town & country pest solutions in Rochester, New York, Matt Fabry spends a lot of time going home to home trying to eliminate people's bedbugs. And for many exterminators, their best ally in this fight is man's best friend. We were one of the first exterminators that actually purchased a trained bedbug dog. Hey! Where's roscoe? He's working! Reporter: Of course you've seen them on TV -- Roscoe, the bedbug dog inspects everywhere. Reporter: The bedbug-sniffing dog has become the first line of counteroffense. And it's no myth. Dogs, with their superior sense of smell, really can be trained to sniff out bedbugs. Still, a study published just last month found that trained dogs smell bed bugs where there are none about 15% of the time. Matt knows that the nose can lead you astray. You just want to make sure that that dog is really exposing a live bedbug, because you can pay a lot of money for false alerts. Reporter: Here's the thing -- Matt says most dogs get rewarded with doggie treats. Good girl! Reporter: So there's the potential for a canine conflict of interest. And if he's really hungry, he's going to do false alerts and go like this, and bark, and there won't be a bedbug there. Reporter: So we at "20/20" decided to put some super-sniffers to the test. This four-floor townhouse in Brooklyn, New York, gave us what we needed. Because we want to know how will bedbug-sniffing dogs and their handlers perform under real-life conditions. There's a lot of inexperienced technicians. They don't get paid enough, whatever. They never get good training. Reporter: In fact, the national pest management association itself lists strengthening the public's perception as one of its goals. Our industry is filled with professionals that are committed to customer satisfaction. And certainly we do recommend that homeowners do their background research, ask for references. Reporter: So, we do our research and bring in two renowned entomologists, Lou Sorkin and Paul Bello, to first confirm the home is bedbug-free. We know that there's no bedbugs here. Reporter: Then we rig the home with five hidden cameras. The stakes are high. If your home is diagnosed with bedbugs, look out -- treatment can cost thousands and disrupt a home for weeks. It's more prudent to confirm that you have an infestation before you take that kind of action, than to just do it simply because a dog alerted. Reporter: So, with cameras rolling, we watch as ten different companies and their prized pooches go to work -- Labradors, beagles, jack russells. The first several teams come and go -- not a single dog finds evidence of bedbugs. Which is great, because there are none. Let's call mike. He smells bugs on the couch, in the bed. The handler rewards him with a treat. But our homeowner wants to know more. You don't do a further inspection? No. You rely on your dog. Yes. If you had to say, like, what percentage of the time she's accurate, what would you say? A percentage? I'll say 90%. So definitely this room would have to be treated. Basically the whole room. Yes. Reporter: Hold it right there. Our experts say mike is wrong. And no treatment is necessary because, had the company bothered to look, they wouldn't have found any bedbugs. We showed the footage to entomologist Lou Sorkin. They have to understand that maybe their dog is playing them and just wants the reward. Reporter: The dog is playing the exterminator? Yes. Reporter: So we crawl out of the woodwork to ask our dog handler some friendly questions. Hi, Paula Faris from ABC and "20/20." I cannot be filmed, sorry. You were going to charge her $2500. Okay, maybe he was just erring on the side of caution by recommending treatment. But then, double-whammy. We meet this dog we'll call "Scout." Scout, too, alerts to bedbugs. He's picking up the scent of live bedbugs. He's saying that to me, yep. So is your dog telling me that I have bedbugs? Is that what your dog is saying to me? He's saying that to me, yep. Reporter: This handler seems to do everything by the book, he even brings in a second dog. We're going to check with the second dog. Reporter: But even the second dog gets it wrong and detects bedbugs. Hot on the scent, the exterminator is eager to find an actual bug for our homeowner. You're gonna show me the bug? Yeah, I'll find it for you. You're gonna promise me you're gonna find a bug based upon your dog. Reporter: He searches and searches, but no luck. So what will he say to our homeowner? I'm not gonna lie to you and say, "Yeah, I found the bedbugs here." But 100% I rely on them. I would highly recommend the treatment. Reporter: Huh. With two dogs alerting, but no visual evidence of bedbugs, this exterminator still recommends his company's expensive treatment. Believe it or not, that actually complies with industry guidelines. Still, we want to hear from him. Uh-oh. Hi, Paula Faris from ABC news and "20/20." We brought in two well-respected entomologists. They did not find any proof of bedbugs. What did you find? I didn't find anything. The dog alert. So, no bedbugs. Why not lay a trap to find proof of life before you recommend an expensive treatment? That's options. I'm not trying to steal money from you or anything like that. Reporter: Okay, anybody can make a mistake. But, after two days of hidden camera work, we find 4 out of 11 dogs are in the doghouse, they get it wrong. The lesson? Make sure that they show you that bedbug and don't just let them tell you it's there and we can't see it. Reporter: So when the bug man cometh, trust -- but verify.
This transcript has been automatically generated and may not be 100% accurate.