Police in Neuchâtel have a new aid in discovering the cause of suspicious fires: Dusty, Switzerland's first "fire investigation dog".
Dusty, a four-year-old springer spaniel, showed off his skills recently by picking out, from five charcoaled carpets, the one that had been treated with a drop of fuel.
Sniffer dogs are already used for detecting drugs, explosives, corpses, smuggled food and for tracking. Fire investigation dogs are trained to locate a variety of flammable liquids among fire debris when arson is suspected.
According to Emre Ertan, Dusty's owner and a fire investigator for Neuchâtel police, arson accounts for only a small percentage of fires.
"I'd say 50 per cent of fires are to do with 'human action' and the others are mainly technical, for example electrical faults," Ertan tells swissinfo. "Out of those human action fires, most are accidents such as cigarettes which aren't put out."
Fire investigators make an initial assessment of the site and then call for the dog if they suspect arson.
"We don't send the dog in on a 'blank' site not knowing what's going on – there's always a preliminary investigation," he says.
Dusty then goes into action once the fire is extinguished and the scene is cold.
Wearing fetching protective boots, he quickly tracks down the vapour given off by any liquid accelerants, substances used to aid the spread of fire such as petrol, kerosene, turpentine and diesel.
He indicates the location of the accelerant by pointing at the source with his nose. A sample is then taken away for forensic laboratory examination.
"Dogs are a great help at a fire site," says Ertan. "They can detect something that analytical instruments won't."
Humans can train their sense of smell, but even the refined nose of an expert wine taster – "Mmm, an oaky body with a hint of meths" – doesn't come anywhere near that of a dog. And then there's a dog's speed.
"If you went to a football pitch and put a drop of petrol on a blade of grass, Dusty would find it in two to three minutes," Ertan explains. "Humans, despite all our analytical instruments, would probably never find it."
A dog's ability to search a large area quickly and efficiently reduces the time an investigator spends on excavating and sampling fire debris and it reduces the number of samples required for expensive forensic testing.
If dangerous chemicals are known to be at the fire scene, dogs could be endangered by smelling debris – asbestos fibres and mineral fibres from insulation are a particular problem – but Ertan denies they are put at unreasonable risk.
"We haven't had any complaints yet," he says. "We know that in Britain the RSPCA [the Royal Society for the Prevention of Cruelty to Animals] made a few inquiries and the dogs were monitored by vets, but they haven't discovered anything suspicious."
"We always do a risk assessment at the site before sending Dusty in – to check that there are no holes for him to fall through," Ertan says. "However, he does wear little boots to protect his paws from broken glass and charred wood."
Doesn't he go berserk near a petrol station? "No, because he's totally conditioned and knows when he's 'at work' – although it's not work for him, it's a game. So when I put his boots and harness on, he goes into game mode and starts searching for petrol."
Ertan admits detection is very tiring for dogs. "They'll work for 15-20 minutes on a cold day and a maximum of ten minutes on a warm day and then they'll need an hour or an hour-and-a-half's rest." Nice work if you can get it. "It's equivalent to a good three- or four-hour walk for us," Ertan adds.
Success does not come overnight, however. Basic dog training takes at least six months and then another six months is needed to get them used to the different accelerants.
Training generally involves a series of exercises where the dog retrieves a hidden object that carries the target scent. He is then rewarded by his handler for a successful "find" – in Dusty's case a mangled tennis ball.
Although all dogs can become sniffers, some breeds are more acquiescent than others.
"Springer spaniels are very easy dogs to train and they'll do anything for their dog-handler – which is not the case with a Belgian shepherd," says Ertan. "Springer spaniels are very motivated to please their handler."
"The idea of the game is that the dog wants to play with his master," he says. "The whole thing works if there's a very strong bond between the dog and the dog-handler."
swissinfo, Thomas Stephens
The nose membranes of dogs are many times more sensitive than those of humans and a much larger part of their brain is dedicated to scent detection.
This is a result of evolution: a keener sense of smell gave a wild dog a competitive advantage in tracking down prey.
Neuchâtel police bought Dusty for SFr5,000 ($4,000) in Britain.
Normally such a dog costs around SFr15,000.
Dusty, a four-year-old springer spaniel, is Switzerland's first fire investigation dog.
A dog can detect fire accelerants more accurately and more quickly than existing technologies.
Since Dusty's success in Neuchâtel, fire investigation dogs have been introduced in cantons Solothurn and Schwyz and two are being trained in Vaud and Bern.
Of the 426 reported fires in Neuchâtel in 2004, 11 were identified as criminal.