Trustees of the Prince George's County library system voted recently to require librarians and other employes to work an extra two and a half hours each week without any increase in pay. In response, library workers, perhaps the least vocal of the county's employes, are taking the unprecedented step of sending a petition to the board members next week.

"I just think it's making a very, very long day," said Betsy Fowler, president of the library's staff association. "Working with the public is wonderful, it's part of the job, but it's not all good. It can be very stressful. I don't think there's any room to increase the stress."

The association informally represents the system's 336 employes, who are not unionized.

Library director William Gordon, who proposed the change from a 37 1/2-hour week to a 40-hour week, said the move is necessary to cope with the financial restrictions of the hard-pressed county. The change, which takes effect in January 1984, would bring library employes' time more in line with that of other county employes, nearly all of whom work a 40-hour week, he said.

"What it boils down to is making our resources go further," he said. "I would have preferred not doing it, but these times are different from the affluent ones of yesteryear. We must adapt."

Adapting to hard realities has been a consistent theme of Gordon's administration of the 21-branch county library system. Gordon, 46, was appointed by the seven-member board of trustees in March 1977, just as activists began to organize around the county's strict property tax limit called TRIM.

Gordon moved quickly to respond to TRIM, and in the last five years has cut more than 100 positions from the system without layoffs or curtailment of library hours. At the same time, he has overseen the opening of three additional branches, including a documents library in the county administration building, and the construction of a new fourth branch.

To provide the staffing for these branches, he has used hourly workers who are paid minimum wages and no benefits. He also has instituted a job-sharing program, and given tasks formerly performed only by librarians to workers without advanced degrees.

The employes, the vast majority of whom are women, have mixed feelings about these changes.

"No one has been laid off, and I think that says a lot for the management," said Fowler.

But other employes, asking not to be named, said the widespread use of part-timers has made some career librarians fearful for their jobs, and fearful even to sign the petition being circulated through the branches this week.

"I feel we need some support," said one librarian assigned to a large branch. "This is not the kind of situation where one can stand alone."

Fowler said the association's decision to petition was not easy, since the group had previously sponsored only social activities.

Library workers' salaries range from $9,800 per year for beginning circulation assistants to $42,605 for branch supervisors with 25 years experience.

Library workers also oppose the 40-hour work week because the change will diminish their vacation and sick leave time, and curtail their participation in a "flexi-time" program.