"All libraries are special, but some are more special than others".
~ J. Leide
What is a special library? Why is one library more special than others?
Over the years, many definitions of special libraries have emerged and varied means of identification. Collection size, narrow fields of interest, staff size and an emphasis on personalized service have all been used at one time or another as identifiers.
In an introductory text published by the Special Library Association, the authors define special libraries "as those information organizations sponsored by private companies, government agencies, not-for-profit organizations, or professional associations" (4). They go on to include units within public and academic libraries with subject specialties.
In the same text, the authors note that information centers were originally defined as "those organizations in which user services invariably involved a deeper understanding of the subject areas of the sponsoring agency than would be the case in the average special library" (4). Today, however, according to the authors of this text "differences between the types of organizations are now largely insignificant" (4).
Large organizations may have several special libraries or information centers - one for the banking and finance department, one for the legal department, and perhaps a technical one for its R&D department. Smaller organizations may have just one librarian on staff (a 'solo' librarian) and that person may be responsible for collections that meet the needs of many departments.
While all librarians today are expected to provide excellent service to their users, the nature of service provision in special libraries differs from public, school or academic libraries. Special librarians are expected to be immersed in the activities and goals of the sponsoring, or 'parent' organization; thus they may take on assignments that other libraries would not, such as conducting research (not just conducting a search), writing reports or helping a top executive draft a speech. A librarian in a school or academic setting would never be expected to do the research and write the report of a student! As public libraries are supported by tax dollars, staff are required to serve all members of the public; special librarians are under no such obligation, and while some welcome the public (typically government agencies and not-for-profit organizations), a great many others are not open to the general public.
There is another significant difference between special libraries and public, school or academic libraries. The latter may be mandated by a legal or policy document from an educational institute or town council which requires them to exist; special libraries, on the other hand, exist because the top management of the parent organization have seen the need for maintaining such services. Change in the leadership or strategic direction of the organization, or budget reductions during economic difficulties, leave special libraries particularly vulnerable.
References: Mount, Ellis and Renée Massoud. Special Libraries and Information Centers: An Introductory Text. Washington, DC, USA: Special Libraries Association, 1999.