In Reply:—

I thank Dr. McMillon for his comments regarding his experience using nasopharyngeal airways during general anesthesia for children undergoing frenectomy. An important consideration, however, is that when using nasopharyngeal airways to deliver anesthetic gases, excess gas will overflow through the mouth, escaping into the environment. Even though no firm evidence suggests that trace concentration of anesthetic agents present a health hazard, there is no definitive proof to the contrary. 1Therefore, the use of uncuffed supraglottic nasal airway devices for the delivery of anesthetic gases potentially increases pollution of the operating room. This makes compliance with the National Institute for Occupational Safety and Health more difficult. 2 

Arnold WP: Environmental Safety Including Chemical Dependency, Anesthesia, 4th edition. Edited by Miller RD. New York, Churchill Livingston, 1994
National Institute for Occupational Safety and Health: Criteria for a recommended standard: Occupational exposure to waste anesthetic gases and vapors. DHEW (NIOSH) Publication No. 77-140. Cincinnati, 1977