If the apllication exits and there are still connections open using Firebird Embedded, then the exit may produce an access violation (0xc0000005 error). The root cause is that the fbembed.dll/fbclient.dll will call fb_shutdown() itself, but one of the other libraries (eg fbintl.dll) may already have been unloaded.
To prevent this, on exit the .NET provider should explicitly call fb_shutdown for any of the native libries loaded (but especially for embedded).
See also "Crash Firebird 2.5.8 Embedded with Firebird Ado.net provider." on Firebird-devel.
(cleaning up the connection pool on exit will also prevent the access violation).