Guidance Concerning Use of Carbon Dioxide for Euthanasia of Small Animals: The Office of Laboratory Animal Welfare has issued PHS Policy on Humane Care and Use of Laboratory Animals guidance to Assured institutions clarifying current requirements regarding the use of carbon dioxide (CO2) as a euthanasia agent for small laboratory animals. Guidance regarding prompt reporting of related serious noncompliance is included. The guidance is contained in a July 17, 2002 notice published in the National Institutes of Health (NIH) Guide for Grants and Contracts (OD-02-062) (external link)