Chapter 15 Unified Threat Management for FortiOS 5.0 : Other Security Profiles considerations : Conserve mode : Conserve mode effects : pass
  
pass
The pass setting allows traffic to bypass the AV proxy and continue to its destination. Since the traffic is bypassing the proxy, no Security Profiles scanning that requires the AV proxy is performed. Security Profiles scanning that does not require the AV proxy continues normally.
Use the pass setting when access is more important than security while the problem is rectified.
Pass is the default setting.