Section 880.2920 - Clinical mercury thermometer(a)Identification. A clinical mercury thermometer is a device used to measure oral, rectal, or axillary (armpit) body temperature using the thermal expansion of mercury.(b)Classification. Class II (special controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to § 880.9 .45 FR 69682, Oct. 21, 1980, as amended at 63 FR 59228, Nov. 3, 1998