TWAIN, UNITED STATES (AFP) - After battling increasingly large and deadly wildfires non-stop for weeks, and with no respite in sight, firefighters in California are admitting they are burnt out.

"After a point, you start getting a little screwy, your mental health doesn't do well," said 55-year-old fire captain David Tikkanen.

"We've been up 14 days with no end in sight," he said as he fought back the flames in Twain, a small community nestled in the California pines, that his team was hosing with water to stop it being consumed by the huge Dixie Fire.

They are in a race to prevent any sparks from spreading in an area so desiccated by drought that the vegetation is a veritable tinderbox.

It is gruelling work, carried out in the middle of a conflagration covering some 80,000ha.

A veteran of 35 years on the job, Captain Tikkanen has found himself facing increasingly massive blazes, a phenomenon he attributes to climate change.

"It's becoming a year-round fire season in California, it's just a matter of time before we have fires going 24/7, all year long," he told Agence France-Presse.

"It makes it more stressful and it's more dangerous," he said, leaning on a rake, his red firefighter helmet perched on his head.

No fewer than 5,400 men and women are battling the Dixie Fire, the biggest conflagration to ravage the state this year.

On the steep roads of northern California, a succession of billboards pay homage to all the "fire heroes".

But with each passing year, their missions get longer and more dangerous, and that takes a mental toll.

"It takes what it takes, everybody has their breaking point, you know," Capt Tikkanen said.

"Some people use alcohol, I don't. I go mountain biking or find some other fun things to do.

"Sometimes you need the external help," he said, without judgment. "I've used it in the past, it saved me."

At the bottom of the hill leading up to Twain, Mr Patrick Dellenback, 36, recuperates after trying to quell several heat sources.

His unit came straight from the Bootleg Fire, a gigantic blaze in neighbouring Oregon, and is on its 12th day on the job. He admits the work can be exhausting, both physically and mentally.

"We've got peer support at work, so if something is really bad we can go to people who are specialised in mental health," he said.

"I try not to bring it home to my wife," said the firefighter, his face blackened with soot.

Behind him, Capt Tikkanen climbed behind the wheel of his car: One of the firefighters from his unit has been taken to the hospital. Nothing serious, but he has to rush to his bedside to check up on him, before driving back up these winding and smoky roads and starting work again.

"It's part of the job," he sighed as he drove off.