In the dark of a business park in Berlin’s Reinickendorf district, about 40 men and women in blue uniforms are standing in two straight lines, awaiting orders. It is 19.00 on a Monday evening and this is where the local branch of the German Federal Agency for Technical Relief (Technisches Hilfswerk or THW) meets.

After a short briefing from team leader Sven Wersoly, they head into a large garage where there is a motorboat, five trucks and piles of equipment – wooden planks, cables, bolt-cutters and chainsaws. The workers chatter as they meticulously check equipment, lifting and sorting the planks, some fiddling with wires. Everybody seems to know exactly what to do. “Discipline is key at the THW,” says ­Wersoly, “because our missions can be extremely dangerous.” And those missions involve sending crack teams of these engineers and technicians to disaster areas around the world where their efficiency wins them – and Germany – admiration and respect.

It’s an unusual mix of order and informality that is at the heart of the group. Though THW is a government agency, its complex job of disaster relief and prevention work is almost exclusively shouldered by volunteers – a concept that’s unique in the world. More than 80,000 Germans, from 18 to 65 years old, meet regularly in their free time, slip into the trademark blue uniforms and train to fight floods, rebuild infrastructure after earthquakes and tsunamis, save people from collapsing houses and even rescue cats from trees.

The reasons for joining are manifold: some simply want to help others, some love to work with heavy machinery, some enjoy the group experience – and almost 13,000 male members commit to six years of THW service instead of conscription. The “blue angels”, as they are often known, are somewhere in between firefighters and soldiers. They locate, search, salvage, clear debris, supply electricity, purify drinking water and construct bridges all around the world.

The agency was founded in 1950 to help the population of the country in the event of an attack. The first foreign mission was to deal with a flood in the Netherlands in 1953. Today, they are regularly called in by international aid organisations: “People expect us to be neat, punctual, organised and good with money,” says Wersoly. “And we are.”

“The role of the THW changed after the end of the Cold War,” says Petra Jenning, team leader for the neighbouring Berlin Steglitz unit. The 41-year-old works for Deutsche Telekom by day and trains with THW in the evenings. “And the number of international missions is increasing steadily,” adds Jenning, who represents her institution at the United Nations Disaster Assessment and Coordination teams (UNDAC). “Often people in disaster areas simply can’t ­believe that a team of German volunteers is coming to rebuild their infrastructure,” adds Wersoly, in an office above the workshop. The fact they are civilians is a great asset – it helps the teams get on with people of different nationalities and religions. “They invite us into their homes, cook for us. And we have to explain the unique concept of the THW over and over again.”

Below, in the garage, Christian Knipphals is checking the lighting equipment in his truck. He is quite proud of the hi-tech “Powermoon” gadget, a large helium-filled balloon with integrated floodlights that floats in the sky looking like a moon and illuminating an area the size of a football pitch.

Not every THW volunteer gets to go on international missions and Knipphals’ war stories consist mainly of being asked by the Berlin police to light a public space on 1 May, in order to avert the traditional riots. Still, the industrial mechanic, aged 29, loves the work. “It builds your character,” he says. “You have the discipline, the technology and the camaraderie – and you know you are doing it for a good cause: to help people.”

Meanwhile, his fellow volunteers are busy building an old-fashioned wooden bar for their canteen. “You do spend some time here,” says Knipphals, who decided to join THW for six years: “So why not make the place homely?”