The White House announced guidelines yesterday for granting hardship exemptions to its retroactive hiring freeze. But there was uncertainty in the Office of Management and Budget, which is in charge of considering appeals, about how many of the thousands of would-be federal workers would qualify for exemptions.

The guideline "leave room [to hire] people who have been honestly, severely injured," said one OMB official. Another, however, interpreted them as requiring a job applicant "to convince both [both] agency's Cabinet official and [OMB Director David A.] Stockman" they should be granted an exemption. President Reagan's first executive order forbade employment to any civilian hired after Nov. 5 and not yet on the job.

One OMB official said he had been barraged by exemption requests from federal personnel officers "from Anchorage to San Juan," and begged for anonymity because "I'm living in fear that some frustrated job-seeker will come in here and blow my brains out."

Yesterday's memorandum from Stockman to heads of all executive departments and agencies said that before an agency can even ask OMB for an exemption, an applicant must meet these conditions:

Produce a written offer of employment from an authorized personnel officer between Nov. 5 and Jan. 20.

Show that not being hired "will result in demonstrable, severe and irreparable financial loss."

Prove that the individual "was prudent" and did not quit another job prematurely or make financial commitments, such as buying a new house, in anticipation of the new job.

Demonstrate that the federal agency was prudent in offering the job while knowing that a freeze was imminent.