Of Norfolk's 40 fire stations, for example, 35 are staffed by part-timers.Which means that the figure in breathing apparatus which looms miraculously through the smoke to save your life may have spent the day being a bus driver or a builder.
Or a headteacher. Sean O'Neill, a fire-fighter in Loddon, a few miles east of Norwich, is acting head of The Denes High School in Lowestoft, Suffolk.
A PE teacher by training (he was at High Melton College in Doncaster in the early Seventies), he moved to Norfolk at the start of his career. Settling in Loddon with his wife, a nurse, and his children who attend local schools, he quickly became a parish councillor, and in 1983 friends at the local fire station persuaded him to join.
Loddon fire station is an unassuming place, built around its one Mercedes fire engine. I visited for the regular Monday drill and found the headteacher looking very much one of the team as they carried out a simulated rescue from a stricken Ford Escort which was on its roof in the yard behind the station. Heavy cutting gear and a good tug from the fire engine was needed.
There wasn't much talk, but everyone knew what to do. "Everything is actually a team-building exercise," says Sean O'Neill. "Communication is such that you don't need a long speech - two grunts and everyone knows what you mean."
This emphasis on, as he puts it, "nobody being above the team" has many parallels and lessons for his work in school. "You learn to value people for their strengths as opposed to harping on their weaknesses. That's what I try to do in school."
Humour, too, is a great reliever of tension. "Whatever the job - perhaps there's been a tragedy - somebody afterwards will read the signs in the others and know just when to make the wisecrack. We are offered counselling, but we feel our best counselling is from each other."
This, too, has its parallels in his school management style. "Humour permeates relationships in the senior management team at The Denes. Anyone taking themselves too seriously is open to a wind-up."
Teachers, all too often, have little contact with people from other walks of life. Sean O'Neill has it in abundance. "Tony is in bottled gas," he says. "So he knows all about that. Ray is a bus driver. Chris is a postman,and he's our mobile address book - when we come to a junction, he knows which way the house numbers run."
These men, and the job they do together, are important in his life. "It's so different from being a head. I can come home from school with my eyebrows meeting in the middle from studying a problem, and then that bleep goes off and I'm mentally refreshed."
Apart from the commitment to the two-hour Monday evening drill, he is on call from 6pm to 6am and at weekends (school functions apart), and all the time for most of the school holidays. He has to attend 65 per cent of the call-outs ("shouts") that come during those times in order to qualify for his annual retainer of #163;1,600, plus #163;10 a shout. "But I don't do it for the money. In France or Germany, I would be an unpaid volunteer."
Last year he was out 160 times, many of them in the holidays. August alone saw him on 22 shouts. Nevertheless, he is proud of the fact that in 15 years in the fire service, he has never missed a school day or event because of his fire-fighting work.
His two worlds rarely meet. "Most of the youngsters in school don't even know I'm a fire-fighter," he says. That said, a group of his pupils once spotted him driving the fire engine, which caused a minor sensation in school the next day.
At least once or twice a week, as he is working in his study at home - perhaps at nine in the evening, preparing the staff bulletin for next day - his bleeper goes off. "It might be a cow in a dyke, a multiple pile-up on the main road, a thatched roof on fire or a puppy with its head stuck down a hole." (All recent happenings.)
He may be back at his desk within the hour, or he may be out until dawn. "I come in wide awake, and have a shower. I can't sleep straight away so I go back to my work, or read."
Some incidents, especially traffic accidents involving children, are deeply distressing, and others - such as the blaze that destroyed Norwich public library some years ago - are dangerous. "I've never felt such intense heat," he recalls. "The building was cooking inside ."
And some shouts verge on the bizarre. An escaped parrot was recently brought down from a tree - only to bite its owner so badly he had to go to hospital. Then there was the time when the intrepid crew tackled a fire by putting a hose down the chimney. Alas, recalls Sean, it was the wrong chimney. "The lady's beautiful white room, with a white carpet, became entirely black. I just remember her apoplexy and the guilt and shame on our faces. "
Next term, he will become headteacher of Leiston High. For the time being,at least, he intends to continue firefighting. "It's important to have a life outside education, and this is something that keeps me sharp. I'm a lucky man, blessed with two jobs that I always wanted to do."