There are many responsible breeders who treat their dogs with care, never over-breed them and ensure they have clean and spacious living quarters and plenty of exercise and personal attention.

Unfortunately, there are also more than 10,000 puppy mills in the United States—and almost all of them promote themselves as "responsible" breeders or promise "home-raised" puppies.

So how do you know which producers might actually be puppy mills?

Despite what they may tell you, many people who sell their puppies online, through the classifieds or to pet stores are actually puppy mill operators. Here's a list of statements commonly made by questionable puppy sellers, and what they may really mean:

Puppy mills say: "My place is hard to find. I'll meet you in the local parking lot."

What they mean is: "I don't want you to see where I keep my dogs."

Be extremely wary of anyone who discourages you from visiting their facility or who invites you to their home or property, but only shows you one puppy at a time. Responsible breeders have nothing to hide and will be glad to show you not only the puppy you are interested in, but his or her parents and the other dogs on the property as well. They will also show you the areas where both the adult breeding dogs and the puppies spend their time. They may ask you to sanitize your hands or shoes before you enter or touch the dogs.

Only the public can stop the cruel cycle of puppy mills ... by refusing to make the purchases that keep underhanded breeders in business.

Truly responsible breeders want to meet their puppy buyers face-to-face and will likely interview you as much as you interview them. They do not sell their puppies to the first person who shows up with cash in hand. They will be proud to show you where they keep their animals—in a clean, spacious and comfortable area.

Puppy mills say: "My puppies come with a health guarantee."

What they mean is: "If you sign this, it limits my liability if your puppy gets sick."

While a health guarantee itself is not a sign of a bad breeder, it's important to read health guarantees or contracts with a critical eye. They are often designed to protect the seller's interests more than yours. They can be full of exclusions and loopholes and often require you to return a sick puppy to the seller in order to get a refund—which might be the last thing on your mind when you are trying to save a sick animal's life. These guarantees often list more exclusions than inclusions.

Pledge to protect puppies and stop cruel puppy mills

Puppy mills force animals to live in deplorable, inhumane conditions with minimal veterinary care or human interaction before being sold to pet stores, middleman brokers or over the internet. You can stop the cycle of cruelty by pledging to adopt your next pet from a shelter or rescue or purchase only from a responsible breeder.

B.B., a dog rescued from a Cabarrus County, North Carolina, puppy mill on 9/26/16
Amie Chou / The HSUS

Puppy mills say: "Our puppies come with a health record on our kennel's letterhead listing all the care we provided."

What they mean is: "We 'play vet' to save money."

A truly responsible breeder will be able to provide you with the name and number of their veterinarian, as well as proof of the puppy’s full veterinary examination on their veterinarian's letterhead. Many will also provide you with health reports and screening results for the puppy's parents. Less reputable breeders will give you a list of treatments they administered themselves, rather than a record from a licensed vet. Amateur breeders who skip veterinary exams to cut costs are likely to be cutting costs elsewhere as well—often at the expense of the dogs in their care.

If the seller has administered their own vaccinations, ask for a detailed explanation. Each vaccination listed on the record should be accompanied by a small label with the expiration date and lot number of the vaccine (which the manufacturers provide in self-stick format with each vaccine for this very purpose). Without these records, you have no proof that the seller administered the correct vaccinations on schedule. Be wary of breeders who take shortcuts.

Too many families have taken home a puppy who had "all his shots" only to have their pet become gravely ill with a disease the pup was supposedly already vaccinated for.

Note that some pet stores or breeders who sell animals across state lines may assure you their puppies come with a "health certificate." A health certificate is not a guarantee that the puppy was fully examined. It is a standard form that is required for any puppy sold commercially across state lines. It only means that the puppy has had a very brief visual inspection by a veterinarian. The inspection usually does not include testing the puppy or his or her parents for genetic disorders, parasites or testing for diseases such as Giardia and Brucellosis, both of which are contagious to humans and are frequently seen in puppy mill puppies.

Puppy mills say: "I am USDA-approved."

What they mean is: "I've met the bare minimum standards required to obtain a license."

There are no USDA "approved" breeders. There are USDA licensed breeders. While having a state or USDA kennel license certainly doesn't make one a puppy mill, neither does possessing a license make one a quality breeder. If a breeder is USDA licensed that means they sell their puppies to brokers or pet stores. Truly responsible breeders do not sell their puppies to pet stores; they want to meet their puppy buyers in person and do not sell their puppies to the first person who shows up with cash in hand.

USDA standards under the Animal Welfare Act are bare minimum survival standards, not optimal standards of care.

Under USDA standards, it is legal to keep dozens or even hundreds of breeding dogs in small wire cages for their entire lives with only the basics of food, water and rudimentary shelter. But many USDA facilities have been found in violation of even these minimal standards. It is extremely rare for the USDA to revoke a commercial breeder's license or even fine a puppy mill that has repeated violations. As a result, there are hundreds of USDA licensed puppy mills in operation that have a history of documented animal care violations that are still licensed.

The best advice, once again, is to visit the facility yourself. If you see breeding dogs in rows of small cages, consider whether this is the life your puppy's mother and father should endure. Those who purchase from these facilities are supporting the way these dogs are kept. Without such buyers, puppy mills could not survive.

Puppy mills say: "Ours is a family business. We raise healthy puppies on our 20-acre farm."

What they mean is: "We produce puppies."

Almost every breeder, even disreputable ones, has a family and many commercial breeders breed puppies on family-owned farms. Don't assume that a website offering "farm-raised" or "family-raised" puppies isn't a puppy mill. Once again, you need to see the property for yourself and view the areas where the dogs are living.

Unfortunately, being raised on a 20-acre farm doesn't mean that the dogs have access to the space. Too often, the breeding dogs at puppy mills are forced to live in small cages on the property; frequently they can see open, grassy spaces but never run and play in them. The parent dogs live behind bars from birth until death, without ever feeling the ground under their feet, enjoying a treat or toy or having loving human contact or proper veterinary care. They are bred repeatedly until they can no longer reproduce and then they are destroyed or discarded.

The real tragedy of puppy mills is that keeping breeding dogs in such a way is, in most cases, perfectly legal. Only the public can stop the cruel cycle of puppy mills, by refusing to buy the puppies that keep these kinds of breeders in business.

Now you know some of the warning signs of a disreputable breeder. Find out more about how to locate a responsible breeder.