5 CFR § 337.205 - Critical hiring needs.
(a)OPM will determine when there is a critical hiring need for particular occupations, grades (or equivalent) and/or geographic locations. OPM may decide independently that such a need exists or may make this decision in response to a written request from an agency.
(1) Identify the position(s) that must be filled;
(2) Describe the event or circumstance that has created the need to fill the position(s);
(3) Specify the duration for which the critical need is expected to exist; and
(4) Include supporting evidence that demonstrates why the use of other hiring authorities is impracticable or ineffective.