An oral capnography accessory device provides a pathway for sampling oral exhalations of carbon dioxide from a mouth of a patient. The device is used in combination with a bite block. The device includes a main body extending linearly along a longitudinal axis, latch arms extending from a buccal facing surface of the main body and forming a cavity into which the bite block is insertable, and tube attachment extending from a lingual facing surface of the main body. Tubing is insertable through a passageway therethrough of the tube attachment. The device is configured for use with a nose or face mask, and with a monitoring system.