diff --git a/definitions/gases.xml b/definitions/gases.xml
index 874c45e..378a8e2 100644
--- a/definitions/gases.xml
+++ b/definitions/gases.xml
@@ -6,14 +6,14 @@
    <!-- Quenchers -->
    <material name="TMAGas" state="gas">
       <D unit="kg/m3" value="6.70" />
-      <composite n="3" ref="C" />
-      <composite n="9" ref="H" />
-      <composite n="1" ref="N" />
+      <fraction n="0.6095775385572637" ref="C" />
+      <fraction n="0.1534682886203227" ref="H" />
+      <fraction n="0.2369541728224135" ref="N" />
    </material>
    <material name="IsobutaneGas" state="gas">
       <D unit="kg/m3" value="2.38467" />
-      <composite n="4" ref="C" />
-      <composite n="10" ref="H" />
+      <fraction n="0.8265819278538703" ref="C" />
+      <fraction n="0.1734180721461297" ref="H" />
    </material>
 
    <!-- Target gases -->
diff --git a/output/materials.xml b/output/materials.xml
index bba40ed..8e9812a 100644
--- a/output/materials.xml
+++ b/output/materials.xml
@@ -3686,14 +3686,14 @@
    </material>
    <material name="TMAGas" state="gas">
       <D unit="kg/m3" value="6.70"/>
-      <composite n="3" ref="C"/>
-      <composite n="9" ref="H"/>
-      <composite n="1" ref="N"/>
+      <fraction n="0.6095775385572637" ref="C"/>
+      <fraction n="0.1534682886203227" ref="H"/>
+      <fraction n="0.2369541728224135" ref="N"/>
    </material>
    <material name="IsobutaneGas" state="gas">
       <D unit="kg/m3" value="2.38467"/>
-      <composite n="4" ref="C"/>
-      <composite n="10" ref="H"/>
+      <fraction n="0.8265819278538703" ref="C"/>
+      <fraction n="0.1734180721461297" ref="H"/>
    </material>
    <material name="HeliumGas" state="gas">
       <D unit="kg/m3" value="0.125"/>
diff --git a/output/rest.xml b/output/rest.xml
index 1bcac2a..308b1c8 100644
--- a/output/rest.xml
+++ b/output/rest.xml
@@ -3161,14 +3161,14 @@
    </material>
    <material name="TMAGas" state="gas">
       <D unit="kg/m3" value="6.70"/>
-      <composite n="3" ref="C"/>
-      <composite n="9" ref="H"/>
-      <composite n="1" ref="N"/>
+      <fraction n="0.6095775385572637" ref="C"/>
+      <fraction n="0.1534682886203227" ref="H"/>
+      <fraction n="0.2369541728224135" ref="N"/>
    </material>
    <material name="IsobutaneGas" state="gas">
       <D unit="kg/m3" value="2.38467"/>
-      <composite n="4" ref="C"/>
-      <composite n="10" ref="H"/>
+      <fraction n="0.8265819278538703" ref="C"/>
+      <fraction n="0.1734180721461297" ref="H"/>
    </material>
    <material name="HeliumGas" state="gas">
       <D unit="kg/m3" value="0.125"/>