+
+[ATA] Health status is obtained by checking the (boolean) result returned
+by the SMART RETURN STATUS command.
+The return value of this ATA command may be unknown due to limitations or
+bugs in some layer (e.g. RAID controller or USB bridge firmware) between
+disk and operating system.
+In this case, \fBsmartctl\fP prints a warning and checks whether any
+Prefailure SMART Attribute value is less than or equal to its threshold
+(see \'\-A\' below).
+
+[SCSI] Health status is obtained by checking the Additional Sense Code
+(ASC) and Additional Sense Code Qualifier (ASCQ) from Informal Exceptions
+(IE) log page (if supported) and/or from SCSI sense data.
+
+[SCSI tape drive or changer] TapeAlert status is obtained by reading the
+TapeAlert log page.
+Please note that the TapeAlert log page flags are cleared for the initiator
+when the page is read.
+This means that each alert condition is reported only once by \fBsmartctl\fP
+for each initiator for each activation of the condition.
+.\" %IF OS FreeBSD Linux Windows Cygwin
+
+[NVMe] [FreeBSD, Linux, Windows and Cygwin only]
+[NEW EXPERIMENTAL SMARTCTL FEATURE]
+NVMe status is obtained by reading the "Critical Warning" byte from
+the SMART/Health Information log.
+.\" %ENDIF OS FreeBSD Linux Windows Cygwin