The charity, founded over 30 years ago as a domestic version of Voluntary Service Overseas, places around 3,000 people a year in full-time work away from home, caring for groups such as young offenders or blind children. Alternatively, volunteers could find themselves caring for an individual with a disability living at home.
But CSV's aim is to help the helper too. The experience, it says, can turn around someone with a difficult background or instil confidence and a sense of direction in young people who have no clear idea of what they want to do with their lives.
The organisation wants more careers advisers, youth workers and Job Centre staff to suggest volunteering to youngsters who are in danger of just wandering into any old job or no job at all. It also stresses its value to job-seekers who have no significant achievement to put on their curriculum vitae apart, perhaps, from academic qualifications.
Catherine Field, of CSV external relations, is in no doubt about the benefits: "People with a tricky background can be quite different after four months. You can see the raised self-esteem and that they know where they're going."
The organisation has a policy of never rejecting anyone, although applicants with criminal records are carefully investigated and interviewed. If a potential recruit has a violent background, CSV, which acts as a recruitment agency for 800 projects, looks for one with a clear structure and plenty of staff. The supervisor is briefed about the applicant's history and has the option of suggesting that he or she go to a different project.
Mora Dickson, co-founder of CSV, makes no apology for the policy established 30 years ago: "It suddenly occurred to us that we might be selecting someone because he'd had the nous to buy The Times on the way to the interview. It doesn't matter whether a volunteer is blind, in a wheelchair or fresh out of prison. These programmes are successful as long as you put someone in the right place."
The potential dangers for volunteers themselves were highlighted a few years ago when a young volunteer - not recruited by CSV - was killed by a disturbed hostel inmate. The dead man's family complained that he had been placed in a dangerous situation without adequate training or support.
CSV volunteers at a Cyrenian community house for homeless single young people in Edinburgh are under the supervision of a social worker, but only during the day from Monday to Friday. Volunteers are given training on how to deal with aggression, on befriending, communication skills and management of stress. They are always on duty with another volunteer.
"When you have people working with people there are always risks," says Miss Field. "But we choose people carefully and provide training and back-up. The risks are calculated ones. "
Adam Withers, 22, is one of the CSV volunteers based at the Cyrenian home.He says he is aware of danger "about
1 per cent of the time" but feels that between fellow volunteers, paid staff, police and other residents, he has adequate support. Dangerous situations are often defused, he says, by the bonds built by volunteers with clients. "If they see you as a person, that helps because it is authority they are angry with, not you."
A recent challenge was sparked by a distraught phone call from an inmate in the city centre. The man, an alcoholic, had just split up with his girlfriend and was threatening suicide. Adam and a fellow volunteer had to find him and persuade him to walk the four miles home. He was angry and aggressive. It took them three hours.
"Volunteering is rewarding and has changed me for the better," says Adam. "I am much more streetwise, more outgoing and more willing to confront people. It has also opened my eyes to the problems of others."
Adam has a business degree but was unable to get a job after graduation. He is much more optimistic about job hunting now, particularly about performance at interviews.
Fellow volunteer Scott Bradley, 26, agrees that the role is an eye-opener."Now I never want to complain about little things like not having money for a pint," he says. On an ordinary day Scott, Adam and colleagues organise the household budget and housework, get inmates out of bed, get them to sign on or go to courses, or perhaps accompany them to a court appearance. Volunteers share an evening meal and exchange banter with clients. In short, they say, they provide friendship and support to some of the most disadvantaged and damaged people in society.
Paul McInneny, 24, freely admits that he thought he wouldn't be able to handle the work on his first day in the special needs unit of Capability Scotland's New Trinity Centre in Edinburgh. Clients in the unit can be very disturbed, constantly crying out for attention or relentlessly staring directly at the volunteer. But after two weeks he was getting hugs and feeling at home.
The first time Paul took a disabled client to the lavatory, he had to leave the room. "But it gets easier," he stresses. He now finds volunteering so satisfying that he has decided to give up a career in Dixons selling computers.
School-leaver Fiona Gould, 19, also found the first couple of days at the centre "scary". As with many volunteers, it was her first time away from home, but now she enjoys feeding and communicating with clients, in sign language if necessary, and helping them with activities ranging from riding, swimming and physiotherapy to leatherwork. Another skill she is acquiring is managing a personal budget of travel expenses, #163;28 for food and #163;23 pocket money.
"It's tough managing on that," says Fiona, who is taking a year out before university. "But I love what I'm doing and have made so many new friends." She has also succeeded in confounding her parents who were doubtful that she could handle her new life. Parents are often anxious about CSV since their children can be as young as 16 and are away between four and 12 months. They ring CSV for more information and hear about the accommodation, supervision and regular social nights which allow volunteers to get to know each other and talk over their experiences.
At the Royal School for the Blind in Edinburgh volunteers do everything from pouring out cereal to accompanying the children to swimming galas. But they are not simply a cheap form of additional staffing. For Kevin Tansley, the head, they bring new ideas, enthusiasm and talent. His colleague, Margaret Dickson, a senior house parent, agrees. "They become part of the body of the school. The kids quickly sense when they are not around and ask for them."
At New Trinity Centre, deputy manager Karen Fraser is also emphatic that volunteers are "not just another pair of hands" but bring a sense of fun, enthusiasm and commitment. She lavishes praise on CSV itself, which she describes as well organised, with good interview skills. She is happy to accept placements on trust without any advance contact between her and the volunteer.
As for employers, CSV says that a survey of 500 top British companies revealed that over 75 per cent felt volunteers would have above average teamwork and communication skills. Linda Kennedy of ICI says: "If people want a management position with ICI, they need to get on with people, manage people and understand how to motivate them. Volunteering provides these skills."
For further information about becoming a volunteer, contact CSV, tel: 0800 374991.