This is an image of the experimental set up the researchers used to sample decomposition odor from pig carcasses. CREDIT Shari ForbesToday’s search-and-rescue teams use incredible technologies to help find trapped victims. Infrared and thermal cameras, sensitive microphones, and geophones that turn ground movement into voltage measurements, just to name a few.

A highly trained dog, however, is often the most effective.

Even with recent advancements in technology, the sniffer dogs are often the most widely used because of their ability to rapidly search large swathes of land, and track odors back to the source.

Researchers now believe they have found the exact time when the scent that the dogs track changes from a living odor profile to a deceased one—a finding that could give search and rescue teams an advantage when searching for both live and deceased victims.

The team, from the University of Technology Sydney, analyzed the scent profile from three domestic pig carcasses that were left out to decompose naturally in the Australian summer. Researchers discovered a significant change in the chemical makeup of the scent after the 43-hour mark, which they believe marks the transition from an antemortem to a postmortem scent profile.

"We were quite surprised to be able to identify so many volatile organic compounds during the early postmortem period," said Prue Armstrong, lead author of the study, in a written statement.

The team hopes the research might help teams decided whether to use human scent dogs that search for living victims, or human remains detection dogs. They even hope the finding might assist in the detection of clandestine graves.

However, decomposition is extremely dependent on environmental factors—like temperature and humidity—making the geographical location of the testing very significant to the findings. In this case, the findings are only relevant to the Australian summer. Researchers have since expanded the environmental conditions.

"Our motivation for the study came from information local law enforcement agencies gave us about using scent-detection dogs to help them find living and deceased victims after mass disasters like earthquakes," Armstrong said.

Researcher identified 105 volatile organic compounds using a relatively new technology, called comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC x GC-TOFMS). The most abundant chemical classes contained either nitrogen, sulfur or ester compounds.

According to the study, human scent is derived from a number of factors: metabolism, genetics, diet, etc. With a trapped victim, the scent can resemble a person who is severely injured, stressed, or even someone who is fasting. For this reason, research has focused on detecting volatile organic compounds (VOC)—organic chemicals that easily break down because of a low boiling point—in a victim’s exhaled air, blood or urine.

"We hope our findings give rescue teams the information they need about the optimal time frame in which to deploy human scent dogs versus human remains detection dogs to best ensure the recovery of victims following a mass disaster," Armstrong said.