diff --git a/fmmd_concept/fmmd_concept.tex b/fmmd_concept/fmmd_concept.tex
index 09c7048..9833725 100644
--- a/fmmd_concept/fmmd_concept.tex
+++ b/fmmd_concept/fmmd_concept.tex
@@ -1148,6 +1148,21 @@ an attribute to the failure~modes must be added
 that can reference other failure~modes and environmental conditions.
 An UML diagram with inhibit conditions added is shown in figure \ref{fig:umlconcept2}.
 
+\subsection{Safe Dangerous, Detected and Undetected.}
+
+The top level or SYSTEM failure modes can be examined and
+assigned SIL~\cite{en61508} safe and dangerous attributes.
+Detected failure modes appear as symptoms that have been 
+integrated into symptoms involving self checking.
+Undetectable failure modes, will follow a direct line
+up from component level to SYSTEM level without being
+incorporated into a self checking functional group.
+These undetected failures correspond to a minimal cut 
+set where a single base~component failure mode
+can be traced to a SYSTEM level failure mode.
+They can thus be determined by searched the DAG
+for a single base~component failure mode minimal cut set~\cite{nucfta}.
+
 % UML DIAGRAM  
 
 \begin{figure}[h]