I found this on the TSA website, If traveling with dry ice:
Questions about the transportation of dry ice generally fall into the hazmat realm where FAA has primary oversight. Since we often get dry ice questions, I felt that it would be a great topic for Travel Tips Tuesday.
My first tip is to check with your airline for any guidance they might have on traveling with dry ice. Dry ice is not prohibited by TSA. Secondly, as far as FAA regulations go, dry ice is permissible when traveling with perishables as long as you adhere to the following guidelines.
Packages of dry ice must allow for the release of carbon dioxide gas.
The limit for dry ice for both carry-on and checked baggage is five-pounds.
Packages of dry ice must contain the language "Carbon Dioxide Solid" or "Dry Ice" and must also have the net weight of the dry ice on the package.
See you next Tuesday with more travel tips!