Safety Concerns of Cold Tests. Concerns have been raised
in the past about the possible damaging effects of cold
testing agents with particular reference to CO2 given its
measured laboratory temperature of −78◦C. Ehrmann [2]
described the “phenomenon of Leidenfrost” that occurs
when a small amount of CO2 snow enters the oral cavity
but causes no harm in spite of its physical contact with the
oral mucosa. This is due to an insulating layer of gaseous
CO2 surrounding the melting mass as the dry ice “film boils”
during sublimation so there is insufficient time for soft tissue
burns to occur.