Aid agencies welcome volunteers to their cause, but fear they will not last the course

When Paddy Maguiness arrived amid the devastation of Banda Aceh, his first report was terse. The most vital need, he said, was "equipment to bury the dead, body bags, masks and breathing equipment, disinfectant and gloves." The other issue of desperate urgency was communications. "They have one satellite phone, and are relying on the mobile network which is intermittent to non-existent.

When Paddy Maguiness arrived amid the devastation of Banda Aceh, his first report was terse. The most vital need, he said, was "equipment to bury the dead, body bags, masks and breathing equipment, disinfectant and gloves." The other issue of desperate urgency was communications. "They have one satellite phone, and are relying on the mobile network which is intermittent to non-existent.

Mr Maguinness does the job that many, many British people felt a sudden urge to do after the scale of the Indian Ocean's tsunami disaster became clear. He's one of the guys who gets the foreign aid flowing. "All sorts of people began calling up," says the young woman at Save the Children recalling the days after Boxing Day. "We got firemen, policemen, all sorts offering help. 'I've given money.' they said, 'but I want to do something concrete ...'

"Everybody was ringing up, wanting to help, to contribute in some tangible way," says Aine Fay, country director of the Irish charity Concern's Indonesian operation.

It's a natural human reaction, though you would probably have to go back to the war in Biafra to find a tragedy that evoked it so powerfully. You see the misery, the destruction, the crying need. You appreciate, with a creeping sense of guilt, the snugness of your own circumstances. Thumbing off a donation doesn't relieve the sense that here you are, embedded in consumer durables, and there they are, homeless, hungry and bereaved. Shouldn't you, couldn't you, be out there doing something?

Well probably not, in all honesty. Yet the need for help is enormous and will continue to grow, simply because this tragedy is so gigantic. "I'm looking at this disaster," says Geoff Poynter of Save the Children, "and I'm thinking, my God, this is going to be a huge operation..." But who should apply, and who would be better off not bothering?

One reason there is a screaming need for help in recent disasters, according to some aid workers in Banda Aceh , is because professionals in this line of work are not being produced in sufficient numbers. The aid trade divides into two main paths, development and emergencies. Development is what the agencies do in normal times: microfinance, education, reproductive health, housing, the long slow slog of raising standards of living in the poorest countries. But emergencies call for very different skills: the ability to move fast without referring up a chain of command, to take decisions instantly, to adapt to difficult and dangerous situations prone to constant change. The United Nations runs courses in emergency work. But there may be no sure way to learn how to do it other than by doing it.

"People are coming through in the development field," says Mr Poynter, "but it may be true that for emergency work there are not enough of them."

"It's highly stressful: nobody wants to do it long term," says Philip Maher, a Canadian who has worked on disasters in 80 countries with the American organisation World Vision. "There's no shortage of people coming here now, but it's a challenge getting people who want to hang in for the long haul."

Mr Maguinness of Concern has been doing it for 24 years, and shows no signs of flagging. He's head of an organisation that turns over €100m a year and he rolled into town with €6m to relieve the disaster. He spent his first three nights in Banda Aceh on wood, grass and concrete respectively. The first man on the ground after a major disaster is in many ways in the same boat as the victims: no hotels, no shops open, no restaurants, no banks, no transport, no nothing. Just a city-wide howl of suffering, and a mission to relieve it.

Since 1968, Concern has grown from nothing to a size that invites comparison with giants such as Oxfam. It goes into disaster zones for the long haul. It is deeply involved in Darfur (remember Darfur?), and even though Indonesia is not one of the world's 40 poorest countries, and therefore not a place on which it would normally focus, the charity plans to stay for three or four years, long enough to achieve something solid.

Concern's concern is helping shattered people put their lives back together again, doing whatever's necessary to make that happen. "We're at the sharp end of implementation," says Mr Maguinness. "The big agencies bring the stuff in the front door; the building materials, the cables, drainage pipes, everything. We're in the camps and in the city as it gets back on its feet, helping people get it installed and up and running."

But that's all weeks, months, years ahead. This week, as so often since quitting his job as a quantity surveyor and joining Concern 24 years ago, he's a pioneer again. It's a task that requires certain qualities of character: pragmatism, sharp wits, a sense of humour, generosity.

Mr Maguinness speaks no Indonesian, but within two days of his arrival in Banda Aceh he found a house to accommodate Concern's forward team - the home of a middle-class family in an area just above the tsunami's high-tide mark. The family was only too happy to move in with relatives in Jakarta in return for a decent rent and full refurbishment.

This city is full of people who have lost everything: relatives, home, money, job, the lot. "One of the first things they need is a cash-for-work programme," he says. "Get local people clearing away the mud and rubble, and pay them for it." And to get Concern up and running here, he's operating a micro version of such a programme himself.

He ran into a Pakistani resident who had worked for the UN for years and who had lost everything in the tsunami and put him to work hunting down another couple of houses. Within a week or two - when Nr Maguinness is back in Belfast - a large complement of Concern staff will be on the ground, and as he says: "Without a place to stay you're stuffed."

The Pakistani's son is an electronics whizz, so he was given the task of sorting out phone lines and an internet connection. A man called Daniel showed up on the doorstep: he was from the devastated town of Meulaboh, and had walked for five days through the mountains to reach Banda Aceh. He spoke passable English, so he became Mr Maguinness's personal assistant. Slowly Concern was clearing itself a space in the jungle.

That's the sharp end of disaster work: the ability to do a bit of everything, a bagload of street smarts, and the brain of a quantity surveyor quietly grinding away in the background, making sure all the numbers make sense.

The UN runs courses in emergency work, but it's not until you are confronted by a city or nation in shock, and have the task of doing something about it, that you discover what's really entailed.