This code system http://hl7.org/fhir/audit-event-severity defines the following codes:

CodeDisplayDefinition
emergency EmergencySystem is unusable. e.g., This level should only be reported by infrastructure and should not be used by applications.
alert AlertNotification should be sent to trigger action be taken. e.g., Loss of the primary network connection needing attention.
critical CriticalCritical conditions. e.g., A failure in the system's primary application that will reset automatically.
error ErrorError conditions. e.g., An application has exceeded its file storage limit and attempts to write are failing.
warning WarningWarning conditions. May indicate that an error will occur if action is not taken. e.g., A non-root file system has only 2GB remaining.
notice NoticeNotice messages. Normal but significant condition. Events that are unusual, but not error conditions.
informational InformationalNormal operational messages that require no action. e.g., An application has started, paused, or ended successfully.
debug DebugDebug-level messages. Information useful to developers for debugging the application.
<status value="active"/><experimental value="false"/><date value="2022-06-06T10:01:24+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="The severity of the audit entry."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/audit-event-severity"/><content value="complete"/><concept><code value="emergency"/><display value="Emergency"/><definition value="System is unusable. e.g., This level should only be reported by infrastructure and should not be used by applications."/></concept><concept><code value="alert"/><display value="Alert"/><definition value="Notification should be sent to trigger action be taken. e.g., Loss of the primary network connection needing attention."/></concept><concept><code value="critical"/><display value="Critical"/><definition value="Critical conditions. e.g., A failure in the system's primary application that will reset automatically."/></concept><concept><code value="error"/><display value="Error"/><definition value="Error conditions. e.g., An application has exceeded its file storage limit and attempts to write are failing. "/></concept><concept><code value="warning"/><display value="Warning"/><definition value="Warning conditions. May indicate that an error will occur if action is not taken. e.g., A non-root file system has only 2GB remaining."/></concept><concept><code value="notice"/><display value="Notice"/><definition value="Notice messages. Normal but significant condition. Events that are unusual, but not error conditions."/></concept><concept><code value="informational"/><display value="Informational"/><definition value="Normal operational messages that require no action. e.g., An application has started, paused, or ended successfully."/></concept><concept><code value="debug"/><display value="Debug"/><definition value="Debug-level messages. Information useful to developers for debugging the application."/></concept></CodeSystem>