[syslog-ng] Reg; Syslog-ng does not recognize the audit facility

Hi Syslog-ng is unable to recognize the facility audit. When I put filter as audit and restart syslog-ng it errors out. When I put the facility code as 13 ,it does not error on restarting the service but does not capture the syslog message received through this filter code 13 as well. Please advise. -- Kaladhar