diff --git a/etc/caseDicts/solvers/chemistry/TDAC/chemistryProperties.cfg b/etc/caseDicts/solvers/chemistry/TDAC/chemistryProperties.cfg
index a781416695..9478f00aa3 100644
--- a/etc/caseDicts/solvers/chemistry/TDAC/chemistryProperties.cfg
+++ b/etc/caseDicts/solvers/chemistry/TDAC/chemistryProperties.cfg
@@ -22,11 +22,11 @@ reduction
 
     // Search initiating set (SIS) of species, needed for most methods
     initialSet
-    {
-        CO;
-        CH4;
-        HO2;
-    }
+    (
+        CO
+        CH4
+        HO2
+    );
 
     // For DAC, option to automatically change the SIS switch from HO2 to H2O
     // and CO to CO2, + disable fuel
@@ -34,9 +34,9 @@ reduction
 
     // When automaticSIS, the method needs to know the fuel
     fuelSpecies
-    {
-        CH4 1;
-    }
+    (
+        (CH4 1)
+    );
 }
 
 tabulation
diff --git a/etc/caseDicts/solvers/chemistry/TDAC/chemistryPropertiesFlame.cfg b/etc/caseDicts/solvers/chemistry/TDAC/chemistryPropertiesFlame.cfg
index fffab2c068..597f33031d 100644
--- a/etc/caseDicts/solvers/chemistry/TDAC/chemistryPropertiesFlame.cfg
+++ b/etc/caseDicts/solvers/chemistry/TDAC/chemistryPropertiesFlame.cfg
@@ -22,11 +22,11 @@ reduction
 
     // Search initiating set (SIS) of species, needed for most methods
     initialSet
-    {
-        CO;
-        CH4;
-        HO2;
-    }
+    (
+        CO
+        CH4
+        HO2
+    );
 
     // For DAC, option to automatically change the SIS switch from HO2 to H2O
     // and CO to CO2, + disable fuel
@@ -34,9 +34,9 @@ reduction
 
     // When automaticSIS, the method needs to know the fuel
     fuelSpecies
-    {
-        CH4 1;
-    }
+    (
+        (CH4 1)
+    );
 }
 
 tabulation
diff --git a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DAC/DAC.C b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DAC/DAC.C
index d20d9f3805..68f179e2c3 100644
--- a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DAC/DAC.C
+++ b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DAC/DAC.C
@@ -35,7 +35,7 @@ Foam::chemistryReductionMethods::DAC<ThermoType>::DAC
 )
 :
     chemistryReductionMethod<ThermoType>(dict, chemistry),
-    searchInitSet_(this->coeffsDict_.subDict("initialSet").size()),
+    searchInitSet_(),
     zprime_(0),
     nbCLarge_(3),
     sC_(this->nSpecie_,0),
@@ -87,22 +87,10 @@ Foam::chemistryReductionMethods::DAC<ThermoType>::DAC
     ),
     forceFuelInclusion_(false)
 {
-    label j=0;
-    dictionary initSet = this->coeffsDict_.subDict("initialSet");
-    for (label i=0; i<chemistry.nSpecie(); i++)
+    const wordHashSet initSet(this->coeffsDict_.lookup("initialSet"));
+    forAllConstIter(wordHashSet, initSet, iter)
     {
-        if (initSet.found(chemistry.Y()[i].member()))
-        {
-            searchInitSet_[j++] = i;
-        }
-    }
-    if (j<searchInitSet_.size())
-    {
-        FatalErrorInFunction
-            << searchInitSet_.size()-j
-            << " species in the initial set is not in the mechanism "
-            << initSet
-            << exit(FatalError);
+        searchInitSet_.append(chemistry.mixture().species()[iter.key()]);
     }
 
     if (this->coeffsDict_.found("automaticSIS"))
@@ -195,52 +183,29 @@ Foam::chemistryReductionMethods::DAC<ThermoType>::DAC
     // According to the given mass fraction, an equivalent O/C ratio is computed
     if (automaticSIS_)
     {
-        dictionary fuelDict;
-        if (this->coeffsDict_.found("fuelSpecies"))
-        {
-            fuelDict = this->coeffsDict_.subDict("fuelSpecies");
-            fuelSpecies_ = fuelDict.toc();
-            if (fuelSpecies_.size() == 0)
-            {
-                FatalErrorInFunction
-                    << "With automatic SIS, the fuel species should be "
-                    << "specified in the fuelSpecies subDict"
-                    << exit(FatalError);
-            }
-        }
-        else
-        {
-            FatalErrorInFunction
-                << "With automatic SIS, the fuel species should be "
-                << "specified in the fuelSpecies subDict"
-                << exit(FatalError);
-        }
+        List<Tuple2<word, scalar>> fuelSpeciesEntry
+        (
+            this->coeffsDict_.lookup("fuelSpecies")
+        );
 
-        if (this->coeffsDict_.found("nbCLarge"))
-        {
-            nbCLarge_ = fuelDict.lookup<label>("nbCLarge");
-        }
-
-        fuelSpeciesID_.setSize(fuelSpecies_.size());
-        fuelSpeciesProp_.setSize(fuelSpecies_.size());
+        fuelSpecies_.setSize(fuelSpeciesEntry.size());
+        fuelSpeciesID_.setSize(fuelSpeciesEntry.size());
+        fuelSpeciesProp_.setSize(fuelSpeciesEntry.size());
         scalar Mmtot(0.0);
 
-        forAll(fuelSpecies_, i)
+        forAll(fuelSpeciesEntry, i)
         {
-            fuelSpeciesProp_[i] = fuelDict.lookup<scalar>(fuelSpecies_[i]);
-            for (label j=0; j<this->nSpecie_; j++)
-            {
-                if (this->chemistry_.Y()[j].member() == fuelSpecies_[i])
-                {
-                    fuelSpeciesID_[i] = j;
-                    break;
-                }
-            }
+            fuelSpecies_[i] = fuelSpeciesEntry[i].first();
+            fuelSpeciesProp_[i] = fuelSpeciesEntry[i].second();
+            fuelSpeciesID_[i] =
+                this->chemistry_.mixture().species()[fuelSpecies_[i]];
             scalar curMm =
                 this->chemistry_.specieThermos()[fuelSpeciesID_[i]].W();
             Mmtot += fuelSpeciesProp_[i]/curMm;
         }
 
+        this->coeffsDict_.readIfPresent("nbCLarge", nbCLarge_);
+
         Mmtot = 1.0/Mmtot;
         scalar nbC(0.0);
         scalar nbO(0.0);
diff --git a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DRG/DRG.C b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DRG/DRG.C
index 0f8337bdc9..a807df2ca2 100644
--- a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DRG/DRG.C
+++ b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DRG/DRG.C
@@ -35,24 +35,12 @@ Foam::chemistryReductionMethods::DRG<ThermoType>::DRG
 )
 :
     chemistryReductionMethod<ThermoType>(dict, chemistry),
-    searchInitSet_(this->coeffsDict_.subDict("initialSet").size())
+    searchInitSet_()
 {
-    label j=0;
-    dictionary initSet = this->coeffsDict_.subDict("initialSet");
-    for (label i=0; i<chemistry.nSpecie(); i++)
+    const wordHashSet initSet(this->coeffsDict_.lookup("initialSet"));
+    forAllConstIter(wordHashSet, initSet, iter)
     {
-        if (initSet.found(chemistry.Y()[i].member()))
-        {
-            searchInitSet_[j++] = i;
-        }
-    }
-    if (j<searchInitSet_.size())
-    {
-        FatalErrorInFunction
-            << searchInitSet_.size()-j
-            << " species in the initial set is not in the mechanism "
-            << initSet
-            << exit(FatalError);
+        searchInitSet_.append(chemistry.mixture().species()[iter.key()]);
     }
 }
 
diff --git a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DRGEP/DRGEP.C b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DRGEP/DRGEP.C
index 13a413bb49..ce765a8e48 100644
--- a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DRGEP/DRGEP.C
+++ b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/DRGEP/DRGEP.C
@@ -36,29 +36,17 @@ Foam::chemistryReductionMethods::DRGEP<ThermoType>::DRGEP
 )
 :
     chemistryReductionMethod<ThermoType>(dict, chemistry),
-    searchInitSet_(this->coeffsDict_.subDict("initialSet").size()),
+    searchInitSet_(),
     sC_(this->nSpecie_,0),
     sH_(this->nSpecie_,0),
     sO_(this->nSpecie_,0),
     sN_(this->nSpecie_,0),
     NGroupBased_(50)
 {
-    label j=0;
-    dictionary initSet = this->coeffsDict_.subDict("initialSet");
-    for (label i=0; i<chemistry.nSpecie(); i++)
+    const wordHashSet initSet(this->coeffsDict_.lookup("initialSet"));
+    forAllConstIter(wordHashSet, initSet, iter)
     {
-        if (initSet.found(chemistry.Y()[i].member()))
-        {
-            searchInitSet_[j++]=i;
-        }
-    }
-    if (j<searchInitSet_.size())
-    {
-        FatalErrorInFunction
-            << searchInitSet_.size()-j
-            << " species in the initial set is not in the mechanism "
-            << initSet
-            << exit(FatalError);
+        searchInitSet_.append(chemistry.mixture().species()[iter.key()]);
     }
 
     if (this->coeffsDict_.found("NGroupBased"))
diff --git a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/PFA/PFA.C b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/PFA/PFA.C
index 6c0228c2c9..7375d0edbb 100644
--- a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/PFA/PFA.C
+++ b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/reduction/PFA/PFA.C
@@ -35,27 +35,12 @@ Foam::chemistryReductionMethods::PFA<ThermoType>::PFA
 )
 :
     chemistryReductionMethod<ThermoType>(dict, chemistry),
-    searchInitSet_(this->coeffsDict_.subDict("initialSet").size())
+    searchInitSet_()
 {
-    label j=0;
-
-    dictionary initSet = this->coeffsDict_.subDict("initialSet");
-
-    for (label i=0; i<chemistry.nSpecie(); i++)
+    const wordHashSet initSet(this->coeffsDict_.lookup("initialSet"));
+    forAllConstIter(wordHashSet, initSet, iter)
     {
-        if (initSet.found(chemistry.Y()[i].member()))
-        {
-            searchInitSet_[j++] = i;
-        }
-    }
-
-    if (j<searchInitSet_.size())
-    {
-        FatalErrorInFunction
-            << searchInitSet_.size()-j
-            << " species in the initial set is not in the mechanism "
-            << initSet
-            << abort(FatalError);
+        searchInitSet_.append(chemistry.mixture().species()[iter.key()]);
     }
 }
 
diff --git a/tutorials/combustion/chemFoam/ic8h18_TDAC/constant/chemistryProperties b/tutorials/combustion/chemFoam/ic8h18_TDAC/constant/chemistryProperties
index ac61548863..fba67e6bec 100644
--- a/tutorials/combustion/chemFoam/ic8h18_TDAC/constant/chemistryProperties
+++ b/tutorials/combustion/chemFoam/ic8h18_TDAC/constant/chemistryProperties
@@ -40,11 +40,11 @@ reduction
 
     // Search initiating set (SIS) of species, needed for most methods
     initialSet
-    {
-        CO;
-        IC8H18;
-        HO2;
-    }
+    (
+        CO
+        IC8H18
+        HO2
+    );
 }
 
 // Tabulation is not effective for single-cell ignition calculations
diff --git a/tutorials/combustion/reactingFoam/RAS/DLR_A_LTS/constant/chemistryProperties b/tutorials/combustion/reactingFoam/RAS/DLR_A_LTS/constant/chemistryProperties
index 332408ad4a..848fb70d2b 100644
--- a/tutorials/combustion/reactingFoam/RAS/DLR_A_LTS/constant/chemistryProperties
+++ b/tutorials/combustion/reactingFoam/RAS/DLR_A_LTS/constant/chemistryProperties
@@ -48,11 +48,11 @@ reduction
 
     // Search initiating set (SIS) of species, needed for most methods
     initialSet
-    {
-        CO;
-        CH4;
-        HO2;
-    }
+    (
+        CO
+        CH4
+        HO2
+    );
 
     // For DAC, option to automatically change the SIS switch from HO2 to H2O
     // and CO to CO2, + disable fuel
@@ -60,9 +60,9 @@ reduction
 
     // When automaticSIS, the method needs to know the fuel
     fuelSpecies
-    {
-        CH4 1;
-    }
+    (
+        (CH4 1)
+    );
 }
 
 tabulation