Temporary-help agencies booming

''Temporaries'' -- that new-use word meaning part-time employees -- represents a booming recession business, growing five times as fast as the nation's labor force. According to the US Bureau of Labor Statistics, there are now more than 2.5 million temporaries working, a 25 percent growth in the past four years.

Although many permanent employees turn to temporary-help agencies when laid off, this has not been the main factor for growth, analysts say. The biggest reason for increases has been the attraction of ''own time'' work, which permits flexible personal schedules and allows time to pursue home duties or other responsibilities.

Employers have bolstered the part-time help market by making greater planned use of temporaries. Companies using this class of worker on a regular basis make savings in testing, recruitment, training, payroll calculations, and fringe benefit deductions. Many of these details are handled by temp-organizations directly with the employees they furnish.

Temporary help demand has broadened beyond the clerical-typist-secretarial stage. New companies have entered the ''temp'' field to provide specialists in health care, word processing, accounting, engineering, and technical expertise for light industry. Old-time and well-known firms in the field have expanded and are prospering.

Kelly Services -- with its Kelly Girl image -- has tripled revenues since 1977 and its profits have doubled. Manpower, largest of this class of firms, now works worldwide with 800 offices in 31 countries.