How Does Scent Work?

We know there is a lot of information in this page. Please read it all to understand how scent really works, and how our Pet Detective and specially trained bloodhounds handle the trail of your missing pet.


Our MOST frequently asked question is

“Has it been too long? Will your dog find a scent?”

As a general rule, we can say, “Yes!” – In almost every case, if it’s within 48-72 hours*. “Usually”, if it’s 72 hours to 2 weeks. “In many cases”, if it’s between 2-4 weeks. “In rare cases”, between 4-12 weeks. BUT, the thing to keep in mind is that even if your pet has been missing for weeks or months, there is a good chance they are still leaving fresh scent in your area (this is especially likely with cats). Remember, that after thousands of hours of searching, your Petsearchers Canada Pet Detective has a pretty good idea as to the “expected” behavior of your pet. So even if we are well beyond the 48-72 hour window, in a broad 2 hour bloodhound Pet Detective search, there is an excellent chance that we will still find a scent – and it’s likely to be far more recent than when your pet went missing, saving valuable tracking time and allowing us to start the search closer to your lost pets current location. Our use of perimeter setting allows us to quickly narrow down the scope of the search to a specific area, meaning lots of ground gets covered in a 2 hour search.


First things first – If you were to ask 50 professional scent dog handlers, you would get 50 different answers. The basics may be similar, but the how long, under what circumstances and certainty of the trail will vary greatly. Tracking and trailing is a skill, and there are very many levels of skill and knowledge in this field. Some handlers claim that scent disappears as soon as 24 hours after it is laid, others claim it can last up to a year – without knowing each handler individually, we have to trust that they believe their claims, based on their dog’s skills and abilities and their skills and abilities as handlers. Our depiction of how scent works is based on our thousands of search hours, hundreds and hundreds of successful finds and many happily reunited families.

Conditions always vary in every search. We have had documented cases of our dogs catching a confirmed six week old scent trail – without any risk of scent carry-in (by owners or multiple pet houses) – in a residential area. We regularly change up the routes in our training, both in busy city areas and rural locations, and regularly train on “old” (but new to the dog) trails. For any search, sooner is better, not just for the scent trail, but also for the safety of your pet and the dangers they can encounter out on the street.

We recommend reading this page here before you continue, about Bloodhounds as Tracking Dogs, to understand how the dogs work and use the scent.

The Basics of Scent

As a broad picture, let’s look at how your missing pet can leave a trail. A scent trail isn’t only left by the pads of your missing pets’ feet; more often, the strongest and most viable path to follow is a combination of skin rafts (dander), fur, drool and breath emitted from their entire body, much like mist or smoke. As an example, picture the smoke from the end of a cigarette as it drifts – it goes a long way, leaving its mark on many spots before it dissipates.

Scent tends to travel in a very similar manner and so it settles into spots, leaves a trace behind as it passes a tree trunk, and can even settle on a leaf several feet above your dog or cats tallest height! Scent is not usually left in a straight path, and if you were to watch our bloodhound work the trail, you would see lots of “back and forth” across the path, sniffing up on shrubs and tree trunks well above your pet’s height, as well as close to the ground.

Many times we have followed our bloodhounds as they are following a scent trail several feet to the right or left of the actual footprints left by our quarry. They may not be “on” the trail, but they are definitely “ON” the trail.

How Weather Conditions Affect Scent

Please note – at the onset of every change of season, each of our scent dogs receive a full refresher training and thorough scent tracking testing to ensure they are fully equipped for the forthcoming season. Regular training and testing in the environments they are working in are paramount to a search dog being successful in their environment.


A common misconception is that the rainy weather we often have here in BC is detrimental to a scent search. Most people are surprised to hear that, in fact, the opposite is true. Our rainy springs, falls and winters are more conducive to searches than the warm summer days. Rain – even quite heavy rain – and cool or warm damp weather are ideal search conditions. The rain and wet actually serve to settle the skin flakes (dander) and other scent particles down to the ground. If it is a torrential downpour, it will usually “pound the scent into the ground” (vegetation); though if the rain ravels scatter the scent, the dog will sort the confusion out by searching for where the track picks back up and continue to follow your lost pet’s path.

Damp air/humidity makes it easier for the hounds system to process the scents, rather than their sensitive olfactory system sniffing in dry, hot dusty air. The moisture also allows for more bacterial action on the scattered skin cells, which means a stronger and longer lasting trail than in dry, hot weather.
Snow is infrequent here, but when it cold, it is often of the utmost importance to find a pet before they succumb to the elements.

Snow is porous and damp, therefore very conducive to a bloodhound scent search. Our bloodhounds have been tested in snowy conditions and have proven every time that snow is no deterrent to a successful search.

Hot Weather

Most of us BC folks look forward to a nice long, hot summer 11 months of the year (ha-ha), but in reality, for our scent tracking dogs, it is the toughest environment to do searches in. We have had many successful searches in the heat – even during the hottest of heat spells – but time really is of the essence in the summer months, much more so than any other time of year.

Basically, sun is scents enemy. Scent is a combination of expelled organisms and bacteria from your pet’s body, left to sit with no sustenance. Without moisture to sustain it, scent is much more quickly “baked off” – dried out and scattered far and wide in the breeze, therefore much more difficult to locate and follow.

In a “concrete jungle” like in the city of downtown Vancouver, summer searches can be difficult after more than a few days. We will generally treat it more as a long lost pet search and strike out looking for fresh scent, as often after 48- 72 hours in a busy, hot, sunny area, a trail is rather tough to follow. In a more residential area, with grass, shrubbery and shaded areas, the scent is protected for a greater length of time, and our hounds are much more likely to catch a trail.
Summer searches are usually more likely to be done earlier in the day or later in the afternoon, as heat also tends to make scent rise. Picture looking at the blacktop on a hot summer day – you can see the heat waves rising up from the ground. The scent trail can sometimes rise higher than the bloodhound’s head – too high to be caught on a hot afternoon, and the scent is brought back down as the temperature cools in the afternoon and evening.


Luckily in BC, our windy weather is almost always accompanied by damp/wet weather, which helps the scent to cling to the area it was initially deposited. Wind may make the track a wild and crazy route, but is rarely enough to eradicate a scent trail.

How Terrain affects scent tracking

The ideal search conditions are in a rarely travelled, cool forested area, with lots of damp underbrush and foliage for the scent to cling to; with very little interference by humans and other dogs and cats.

Most often, the trail is in a city area, with cement, cars and construction going on and has usually been contaminated by owners out looking for their pet before they call us, vehicle exhaust and numerous other animals (raccoons, other dogs and cats, coyotes), along with countless other scenarios. Our dogs have been trained and excel at ignoring the interference; they are focused on following the scent blueprint they have stored.

The length of time that a trail is workable depends a lot on the terrain – let’s picture the smoke drifting from the end of a cigarette again. On a city street, with lots of people and animals, vehicle exhaust, perfumes and dust, the scent has limited surface area to settle on/into where it won’t be contaminated and overrun with other scents over time. In a more residential area, there is often grass beside the sidewalks and bushes and trees along the trail where the scent can settle and be somewhat protected from contamination as well as much less introduction of contaminants from overall area activity.

As the trail ages, there can be spots in the scent path that are eradicated, and this is often when you will see our bloodhounds using Air Scenting to attempt to pick up the trail again.

In Summary

No Pet Detective can ever offer any type of guarantee, other than that of their skills and abilities. Scent is a science, but bloodhounds, the actions of your pet, time and the environment are infinite variables that can change the outcome of any search.
At the very minimum, you know that by hiring Petsearchers Canada Pet Detectives, you can feel confident that you have explored every avenue possible to bring your pet home safely.