A springer spaniel trained to sniff out if fires are started deliberately is in the finals of a UK award for hero dogs.
Sammy has helped with more than 500 investigations by South Wales Fire and Rescue Service.
Seven of the cases turned out to be murder scenes, after Sammy nosed in on suspicious circumstances.
Trainer Matt Jones, 32, of Usk, Monmouthshire, said before the Dogs Trust awards on Monday: "He is very passionate for his work."
Sammy, who is eight, has lived with Mr Jones since he was one and has been trained by him to home in on a range of materials often used to start fires.
He can detect the presence of petrol, diesel, paraffin, white spirit, barbecue fluid, turpentine, acetone, lighter fluid and ethanol up to two weeks after a blaze.
Mr Jones said: "He gives a passive indication that something is there. He stares at what he has found. He is very accurate, to one or two inches."
Crime scene investigators then take a sample from the area and put it through laboratory tests to determine which of the substances is present.
But Sammy's real talent is detecting the presence of these materials in minuscule quantities, at traces 200 times smaller than a grain of sugar.
Mr Jones said: "The dog's ability is above what science can detect."
Sammy's training is based on a reward system. In his case, the reward is to play with his favourite toy, a tennis ball.
Mr Jones said: "He loves his tennis ball. He will never give it back once he's got it."
The pair usually investigate a fire as soon as it has stopped smouldering and has cooled down, said Mr Jones.
Even so, Sammy wears a pair of boots to protect his paws against any sharp items or hot embers.
Sammy is the third fire dog Mr Jones has trained and the four-legged fire service employee is helping to train his apprentice, a cocker spaniel called Bow.
Mr Jones said: "Sammy is probably the best one I've had out of the three. It's his ability and his drive. That is all he really lives to do - work.
"He is constantly searching, sniffing out and smelling."
A Dogs Trust spokeswoman said: "The annual awards ceremony recognises dogs that have performed outstanding acts of bravery, dedication or devotion and Sammy has been selected as a finalist out of hundreds of entries."