# What's the minimum amount of dope dogs can smell? **URL:** \ **Category:** Factual Questions\ **Created:** [May 1, 2015, 6:26am UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972 "2015-05-01T06:26:39Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Tron](https://avatars.discourse-cdn.com/v4/letter/t/3da27b/32.png) [@Tron](https://boards.straightdope.com/u/Tron)\ **Post date:** [May 1, 2015, 6:26am UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/1 "2015-05-01T06:26:39Z")
I’ve always wondered this, even before my pot-smoking days… I’ve asked this before but got no reply: How little marijuana can dogs smell? An ounce; a joint; a seed??? What is the minimum amount of marijuana you can carry that can’t be sniffed by dogs? (Seriously.) ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [May 1, 2015, 10:00am UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/2 "2015-05-01T10:00:08Z")
On a local TV show about NZ Customs, they regularly point out that the Drug Sniffing dogs will indicate on people who have recently used but are not currently carrying illegal drugs (up to several weeks), so for all practical purposes, there is no safe limit. I have also heard of cases of people caught with a few seeds in the treads of their shoes. Dog have noses that are many, many times more sensitive than ours. ---
**Author:** ![grude](https://avatars.discourse-cdn.com/v4/letter/g/e47774/32.png) [@grude](https://boards.straightdope.com/u/grude)\ **Post date:** [May 1, 2015, 12:15pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/3 "2015-05-01T12:15:04Z")
Drug sniffing dogs have such sensitive noses they can even smell drugs when none are present! [https://secure.ucdmc.ucdavis.edu/welcome/features/2010-2011/02/20110223\_drug\_dogs.html](https://secure.ucdmc.ucdavis.edu/welcome/features/2010-2011/02/20110223_drug_dogs.html) ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [May 1, 2015, 1:15pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/4 "2015-05-01T13:15:13Z")
Yeah, mostly it’s the “Clever Hans” effect, where the handler decides who needs searching and the dog cues off that. ---
**Author:** ![MikeF](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@MikeF](https://boards.straightdope.com/u/MikeF)\ **Post date:** [May 1, 2015, 6:32pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/5 "2015-05-01T18:32:59Z")
Hey Bill Door - have you ever seen a drug dog work? I have. Many, many times. There is little doubt, even to the untrained eye, when a dog indicates on where drugs are (or were). Does the “Clever Hans” thing happen? I’m sure it does but to say its mostly that is more than a bit of a stretch. ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [May 1, 2015, 7:00pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/6 "2015-05-01T19:00:59Z")
I saw some testimony about fire sniffing dogs, and the handlers are careful not to influence the dog. The dog gives an unambiguous sign if he sniffs an accelerant: he sits. In their training, they don’t get their treat (in this case, a game of tugging on a rag) unless they’re right. They learn that a false ID will get them nothing. ---
**Author:** ![fire\_hazard](https://avatars.discourse-cdn.com/v4/letter/f/6de8d8/32.png) [@fire\_hazard](https://boards.straightdope.com/u/fire_hazard)\ **Post date:** [May 1, 2015, 11:35pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/7 "2015-05-01T23:35:58Z")
Hi, don’t ever take that chance. Seriously. A well trained dog of a suitable breed can easily identify where something was. Finding where it is now is trivial. Seriously. Take care… don’t take chances… ---
**Author:** ![DinoR](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dinor/32/2821_2.png) [@DinoR](https://boards.straightdope.com/u/DinoR)\ **Post date:** [May 2, 2015, 12:14am UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/8 "2015-05-02T00:14:37Z")
> [@RealityChuck](#): > > The dog gives an unambiguous sign if he sniffs an accelerant: he sits. In their training, they don’t get their treat (in this case, a game of tugging on a rag) unless they’re right. They learn that a false ID will get them nothing. Similarly someone I knew worked as part of a canine unit. His dog was explosives sniffing. False positives weren’t an excuse to search they meant evacuating buildings and involving the bomb squad. A false positive counted against them the same as missing something in training and certification. The dog learned being right is what mattered. He was pretty good at getting it right. ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [May 2, 2015, 7:12pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/9 "2015-05-02T19:12:20Z")
> [@MikeF](#): > > Hey Bill Door - have you ever seen a drug dog work? I have. Many, many times. There is little doubt, even to the untrained eye, when a dog indicates on where drugs are (or were). Does the “Clever Hans” thing happen? I’m sure it does but to say its mostly that is more than a bit of a stretch. [Here you go.](http://articles.chicagotribune.com/2011-01-06/news/ct-met-canine-officers-20110105_1_drug-sniffing-dogs-alex-rothacker-drug-dog) 56% misses, 44% hits. Mostly is as mostly does. Surprisingly, a 92% miss rate with Hispanic drivers. Either the dogs are racist, or they’re cueing off the handler’s bias. Clever Hans fooled a lot of people, and it’s even easier when those people have a vested interest in the dog smelling dope. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [May 4, 2015, 5:01pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/10 "2015-05-04T17:01:02Z")
> [@DinoR](#): > > Similarly someone I knew worked as part of a canine unit. His dog was explosives sniffing. False positives weren’t an excuse to search they meant evacuating buildings and involving the bomb squad. A false positive counted against them the same as missing something in training and certification. The dog learned being right is what mattered. He was pretty good at getting it right. Do those same penalties for a false positive apply in the case of drug sniffing dogs? The handlers have very different sets of incentives in an explosives case where a building is likely to be evacuated than they do in a case where all that will happen in case of a false positive is that someone gets searched for no reason. Are handlers likely to lose their jobs if they get too many false positives that result in someone being searched? Or can the handler use some excuse, such as that the suspect must have had drugs at some point, and expect to be believed, especially if the suspect is someone who might stereotypically be expected to be around drugs? The handlers wouldn’t necessarily have to be consciously trying to influence the dogs. I wouldn’t be at all surprised if dogs could pick up on subtle cues that its handler is less comfortable around people of a particular race. It’s also possible that people of demographics more likely to be falsely targeted by a sniffer dog know this (consciously or not), and are more nervous around the dog. Or they might know that they are likely to face more serious penalties than people of other demographics, and be more nervous for that reason. I wouldn’t consider it irrational if a young black man, for example, were more nervous around police officers than I, a middle-aged white woman, might be. Dogs can tell when people are nervous. ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [May 4, 2015, 5:16pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/11 "2015-05-04T17:16:30Z")
Drug detecting dogs that alert on people carrying marijuana in areas where it is legal may need to be replaced with newly trained dogs that do not alert on pot. Medford Oregon has already asked for money for new dogs trained on heroin, cocaine, etc. but not pot. > [@](#): > > The issue arises because drug-sniffing dogs are often used to provide leads — probable cause — that can allow police to search people or property for drugs. If a suspect were carrying marijuana and heroin and a dog trained to smell both indicated the presence of a drug, any arrest could be invalidated, because the dog may have been smelling legal marijuana. > > Because it’s difficult to retrain a dog on what to search for with its nose, one or both dogs may be phased out. Medford police have requested $24,000 in the upcoming city budget for new dogs trained to smell only heroin, cocaine and methamphetamine, and not marijuana. Each dog costs $12,000, an amount that includes extensive training and certification. [http://www.seattletimes.com/seattle-news/medford-police-may-have-to-retire-their-pot-sniffing-dogs/](http://www.seattletimes.com/seattle-news/medford-police-may-have-to-retire-their-pot-sniffing-dogs/) ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [May 4, 2015, 5:54pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/12 "2015-05-04T17:54:24Z")
Cuing aside, the acuity of the dogs’ noses is nkt in doubt. In tests, they can tell which direction a person walked through a room after smelling as few as three steps, because the smell is stronger in the more recent direction. ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [May 4, 2015, 7:46pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/13 "2015-05-04T19:46:45Z")
> [@Sailboat](#): > > Cuing aside, the acuity of the dogs’ noses is nkt in doubt. In tests, they can tell which direction a person walked through a room after smelling as few as three steps, because the smell is stronger in the more recent direction. Nobody doubts the ability of dogs to smell things, I doubt that dogs are sufficiently well trained to avoid false positives and it is irresponsible to use a indication by one as probable cause. You saw the report above where 92% of Hispanic drivers searched after a dog alert were not found to be carrying drugs. ---
**Author:** ![Blue\_Blistering\_Barnacle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_blistering_barnacle/32/3386_2.png) [@Blue\_Blistering\_Barnacle](https://boards.straightdope.com/u/Blue_Blistering_Barnacle)\ **Post date:** [May 4, 2015, 11:33pm UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/14 "2015-05-04T23:33:17Z")
According to John Bradshaw, although dogs are waaaay better at smelling than humans, they are merely average for mammals. But they are very trainable. Now if someone comes at you with a drug sniffing bear… > **[Dog Sense: How the New Science of Dog Behavior Can Make You A Better Friend to...](https://www.amazon.com/Dog-Sense-Science-Behavior-Better/dp/B0064X82SY)** > > Buy Dog Sense: How the New Science of Dog Behavior Can Make You A Better Friend to Your Pet on Amazon.com ✓ FREE SHIPPING on qualified orders ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [May 5, 2015, 12:48am UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/15 "2015-05-05T00:48:19Z")
My understanding is dogs can smell in the ppt range (parts per trillion). I have no idea what that means for drug users, but people have gotten checked out for smelling like weed they smokes a few days in the past before they ran into the dog. Plus as others have said police dogs are not too reliable. ---
**Author:** ![Siam\_Sam](https://avatars.discourse-cdn.com/v4/letter/s/d78d45/32.png) [@Siam\_Sam](https://boards.straightdope.com/u/Siam_Sam)\ **Post date:** [May 5, 2015, 1:53am UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/16 "2015-05-05T01:53:04Z")
Once when arriving at the international terminal at LAX, we were standing near a young lady picking up her luggage from the belt when a passing drug-sniffing dog started checking her out. Not her bags but she herself. She claimed she’d just come from Nepal and had been around people who were smoking weed. ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [May 5, 2015, 2:02am UTC](https://boards.straightdope.com/t/whats-the-minimum-amount-of-dope-dogs-can-smell/718972/17 "2015-05-05T02:02:59Z")
Tracking dogs are actually smelling shedded skin cells from your body. Friggin’ dead skin cells!