25 Pa. Code § 227a.16
Each area or room containing a radiation-producing device where an individual may receive 2 mrem (0.02 mSv) in any 1 hour or 100 mrem (1 mSv) per year shall be conspicuously posted with a sign or signs bearing the radiation symbol and ‘‘CAUTION RADIATION—THIS EQUIPMENT PRODUCES RADIATION WHEN ENERGIZED,’’ or words having a similar intent.
This section cited in 25 Pa. Code § 227a.3 (relating to exemptions); and 25 Pa. Code § 227a.51 (relating to bomb detection radiation-producing devices).