IT was a sound he'd only heard once before in his life, just half an hour earlier. A terrifying cacophony "like a thousand runaway trains speeding towards me". But on second hearing the noise was worse. Because this time he knew what it was.

New York firefighter Richard 'Pitch' Picciotto was in the stairwell on the seventh floor of the World Trade Centre's north tower. When he'd heard the thunderous crash 30 minutes earlier, at 9.59am on September 11, 2000, he couldn't make sense of it.

The rest of the world knew: we watched in horror as the south tower collapsed. A stunned Pitch learned what had happened a few seconds later via his two-way radio.

So when the noise started again directly above him, far louder this time and accompanied by a blast of wind, it was a chilling moment.

"There were a lot of difficult points that day," he said, with remarkable understatement. "One of the two most traumatic moments was when that noise started again and I knew the tower was collapsing.

"That was the realisation that I was going to die in a couple of seconds. That's what I thought."

He tore down the stairs for dear life as the solid earth beneath his feet turned into a torrent of rubble. Seconds later, all was silence and darkness. Amazingly he had survived without serious injury.

But any elation was followed by the other lowest point of this fireman's difficult day. "I then realised I'm stuck in a void, in a cavity, and there's who knows how many tonnes of debris on top of me.

"I thought no one's ever going to get to us. It's impossible to get to us before we suffocate, or starve, or there's a secondary collapse."

Pitch spent several hours in the blackness. Above and below him were other survivors: firefighters, one of whom died from his injuries; a police officer; and a Brooklyn grandmother who they were helping down the stairs at the time the tower fell.

It took an age for anyone to respond to Pitch's Mayday calls, and even then it seemed that the chance of a rescue team finding them amid the 50-acre wasteland of Ground Zero was slim.

How did he get through those bleakest hours? "You just do. Now, it's day by day. Then it was minute by minute."

Even when blue sky suddenly appeared in the rubble above them, and a chance to escape opened up with it, their route to safety was extraordinarily hazardous. When Pitch scrambled through the opening, he found himself 40 feet above the worst scene of devastation imaginable.

Although drained to the point of exhaustion, and almost blinded by the dust, Pitch managed to lead some of his party to solid ground, and then despatched rescuers to get the rest. He was the highest-ranking firefighter to survive the collapse of the twin towers.

It's a story of epic heroism. "Like most firemen, you kinda shy away from that word hero," he said.

"My daughter said most children of firemen feel that their fathers are heroes; they're extraordinary people because of the calling they have."

Now, seven months on, he can still barely come to terms with what happened the day terrorists plunged two planes into New York's highest skyscrapers. It seems a long way from his present location: sipping iced tea in York's Moat House hotel, overlooking tourist boats gliding along the Ouse.

"It's dream-like. I don't believe it's happened.

"You see the film, I see the film. Every time I see that I can't believe I was in that building and survived."

The knowledge that his actions saved the lives of many of his colleagues "makes me feel good," he said. But 343 firefighters did not make it out. Those like Pitch who did are condemned to rerun the experience over and over.

"There's this guilt thing that goes on after a lot of fires when someone dies. Maybe I could've pushed a little bit more, maybe I could've done this a little bit faster.

"With this tremendous loss of life that's magnified. I have relived a lot of the decisions that I took and, given the same circumstances, I believe I would make every decision exactly the same."

Has he sought counselling? He nods. "I spoke to a few people. We've been through some tough times. I refused to count how many friends and co-workers I lost.

"A lot of guys are having natural reactions, which range from depression, sleep disorders, flashbacks.

"I think about it all the time."

As he was recovering from his injuries, he started to write everything down. "It was very cathartic. It helped me to go through this grieving process." These notes have now been turned into a gripping book, Last Man Down: The Fireman's Story. Dedicated to the firefighters who lost their lives, and with a portion of the proceeds going to relevant charities, Pitch promoted the book at his first-ever signing session in Borders, Davygate, York, on Wednesday night. It is published in the States later this month.

The book is a vivid and often heartstopping account of one man's September 11. It opens in the suburban home he shares with his wife Debbie and their two children as he rushes off to a routine shift at his New York firehouse, and ends in his hospital bed.

Soon after arriving for work, the first plane struck the World Trade Centre. Pitch immediately knew he had to go. He had been the second chief on the scene after a bomb exploded in the basement car park of the twin towers in 1993 - invaluable experience.

When he arrived, he realised those trapped above the fire were lost, but led a company up the north tower to rescue office workers stuck further down. After the south tower collapsed, he took the difficult decision to abandon any further rescue attempts and evacuate the north tower. "We had to leave," he says sadly; "we had to leave."

On the way down through the now deserted lower floors he came across two extraordinary sights. The first was a room full of office workers who were disabled, or too old or too weak to make it out alone. The firefighters helped them down to safety.

The second was a lone broker, still frantically banging away on the keys of his computer. Pitch had to manhandle him out.

His story is a tribute to the courage of the firefighters in New York that day, and across the world. "If you are a fireman, you're part of a shared brotherhood," he said, before meeting members of York's fire service.

Unsurprisingly, Pitch is fully behind the "war on terrorism" launched by the US and backed by Britain after September 11. "We have to eliminate terrorism," he said.

"We have to eliminate terrorists trying to destroy our civilised way of life.

"We have a military power. We don't abuse it. But don't think we won't use it, especially if a country or people or an organisation are going to try to hurt our innocent people."

After promoting his book, Commander Richard Picciotto will return to his post with the New York fire department; but not for too long.

"I will probably retire soon, and hopefully enjoy life," he said. "Life is precious."

- Last Man Down: The Fireman's Story by Richard 'Pitch' Picciotto with Daniel Paisner, published by Orion, at £16.99.

Updated: 10:59 Friday, April 12, 2002