diff --git a/applications/utilities/preProcessing/setExprFields/setExprFields.C b/applications/utilities/preProcessing/setExprFields/setExprFields.C
index 88cbc149b3..9a7ba3dfcd 100644
--- a/applications/utilities/preProcessing/setExprFields/setExprFields.C
+++ b/applications/utilities/preProcessing/setExprFields/setExprFields.C
@@ -678,7 +678,7 @@ int main(int argc, char *argv[])
     }
 
     // Disable dimension checking during operations
-    dimensionSet::debug = false;
+    dimensionSet::checking(false);
 
     #include "createNamedMesh.H"
 
diff --git a/src/OpenFOAM/db/Time/TimePaths.H b/src/OpenFOAM/db/Time/TimePaths.H
index 58dc264403..f1b72fecbf 100644
--- a/src/OpenFOAM/db/Time/TimePaths.H
+++ b/src/OpenFOAM/db/Time/TimePaths.H
@@ -197,7 +197,6 @@ public:
 
         //- Search the case for the time closest to the given time
         instant findClosestTime(const scalar t) const;
-
 };
 
 
diff --git a/src/OpenFOAM/db/Time/TimeState.H b/src/OpenFOAM/db/Time/TimeState.H
index 188cb4b7d7..34d3bc1697 100644
--- a/src/OpenFOAM/db/Time/TimeState.H
+++ b/src/OpenFOAM/db/Time/TimeState.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2018 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -92,13 +92,13 @@ public:
             inline scalar timeOutputValue() const;
 
             //- Return current time index
-            inline label timeIndex() const;
+            inline label timeIndex() const noexcept;
 
             //- Return time step value
-            inline scalar deltaTValue() const;
+            inline scalar deltaTValue() const noexcept;
 
             //- Return old time step value
-            inline scalar deltaT0Value() const;
+            inline scalar deltaT0Value() const noexcept;
 
             //- Return time step
             inline dimensionedScalar deltaT() const;
@@ -109,12 +109,12 @@ public:
 
         // Check
 
-            //- Return true if this is a write time
-            inline bool writeTime() const;
+            //- True if this is a write time
+            inline bool writeTime() const noexcept;
 
             //- Deprecated(2016-05) return true if this is a write time.
             //  \deprecated(2016-05) - use writeTime() method
-            inline bool outputTime() const { return this->writeTime(); }
+            bool outputTime() const noexcept { return this->writeTime(); }
 };
 
 
diff --git a/src/OpenFOAM/db/Time/TimeStateI.H b/src/OpenFOAM/db/Time/TimeStateI.H
index c26dc49f17..bf9dd0f5c4 100644
--- a/src/OpenFOAM/db/Time/TimeStateI.H
+++ b/src/OpenFOAM/db/Time/TimeStateI.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -33,19 +34,19 @@ inline Foam::scalar Foam::TimeState::timeOutputValue() const
 }
 
 
-inline Foam::label Foam::TimeState::timeIndex() const
+inline Foam::label Foam::TimeState::timeIndex() const noexcept
 {
     return timeIndex_;
 }
 
 
-inline Foam::scalar Foam::TimeState::deltaTValue() const
+inline Foam::scalar Foam::TimeState::deltaTValue() const noexcept
 {
     return deltaT_;
 }
 
 
-inline Foam::scalar Foam::TimeState::deltaT0Value() const
+inline Foam::scalar Foam::TimeState::deltaT0Value() const noexcept
 {
     return deltaT0_;
 }
@@ -63,7 +64,7 @@ inline Foam::dimensionedScalar Foam::TimeState::deltaT0() const
 }
 
 
-inline bool Foam::TimeState::writeTime() const
+inline bool Foam::TimeState::writeTime() const noexcept
 {
     return writeTime_;
 }
diff --git a/src/OpenFOAM/db/Time/timeSelector.C b/src/OpenFOAM/db/Time/timeSelector.C
index 37b199bb0d..7fcdc02263 100644
--- a/src/OpenFOAM/db/Time/timeSelector.C
+++ b/src/OpenFOAM/db/Time/timeSelector.C
@@ -33,12 +33,6 @@ License
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
-Foam::timeSelector::timeSelector()
-:
-    scalarRanges()
-{}
-
-
 Foam::timeSelector::timeSelector(const std::string& str)
 :
     scalarRanges(str)
diff --git a/src/OpenFOAM/db/Time/timeSelector.H b/src/OpenFOAM/db/Time/timeSelector.H
index f4a84e10be..b7280b4453 100644
--- a/src/OpenFOAM/db/Time/timeSelector.H
+++ b/src/OpenFOAM/db/Time/timeSelector.H
@@ -82,7 +82,7 @@ SourceFiles
 namespace Foam
 {
 
-// Forward declarations
+// Forward Declarations
 class argList;
 class Time;
 
@@ -98,11 +98,11 @@ public:
 
     // Constructors
 
-        //- Construct null
-        timeSelector();
+        //- Default construct
+        timeSelector() = default;
 
         //- Construct by parsing string for time ranges
-        timeSelector(const std::string& str);
+        explicit timeSelector(const std::string& str);
 
 
     // Member Functions
@@ -165,7 +165,6 @@ public:
             Time& runTime,
             const argList& args
         );
-
 };
 
 
diff --git a/src/OpenFOAM/dimensionSet/dimensionSet.C b/src/OpenFOAM/dimensionSet/dimensionSet.C
index 770af48b84..617b3439be 100644
--- a/src/OpenFOAM/dimensionSet/dimensionSet.C
+++ b/src/OpenFOAM/dimensionSet/dimensionSet.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2017-2019 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -202,7 +202,7 @@ bool Foam::dimensionSet::operator!=(const dimensionSet& ds) const
 
 bool Foam::dimensionSet::operator=(const dimensionSet& ds) const
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("(a = b)", *this, ds);
     }
@@ -213,7 +213,7 @@ bool Foam::dimensionSet::operator=(const dimensionSet& ds) const
 
 bool Foam::dimensionSet::operator+=(const dimensionSet& ds) const
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("(a += b)", *this, ds);
     }
@@ -224,7 +224,7 @@ bool Foam::dimensionSet::operator+=(const dimensionSet& ds) const
 
 bool Foam::dimensionSet::operator-=(const dimensionSet& ds) const
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("(a -= b)", *this, ds);
     }
@@ -253,7 +253,7 @@ bool Foam::dimensionSet::operator/=(const dimensionSet& ds)
 
 Foam::dimensionSet Foam::min(const dimensionSet& ds1, const dimensionSet& ds2)
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("min(a, b)", ds1, ds2);
     }
@@ -264,7 +264,7 @@ Foam::dimensionSet Foam::min(const dimensionSet& ds1, const dimensionSet& ds2)
 
 Foam::dimensionSet Foam::max(const dimensionSet& ds1, const dimensionSet& ds2)
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("max(a, b)", ds1, ds2);
     }
@@ -275,7 +275,7 @@ Foam::dimensionSet Foam::max(const dimensionSet& ds1, const dimensionSet& ds2)
 
 Foam::dimensionSet Foam::clip(const dimensionSet& ds1, const dimensionSet& ds2)
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("clip(a, b)", ds1, ds2);
     }
@@ -325,7 +325,7 @@ Foam::dimensionSet Foam::pow
     const dimensionedScalar& dS
 )
 {
-    if (dimensionSet::debug && !dS.dimensions().dimensionless())
+    if (dimensionSet::checking() && !dS.dimensions().dimensionless())
     {
         FatalErrorInFunction
             << "Exponent of pow is not dimensionless" << endl
@@ -344,7 +344,7 @@ Foam::dimensionSet Foam::pow
 {
     if
     (
-        dimensionSet::debug
+        dimensionSet::checking()
      && !dS.dimensions().dimensionless()
      && !ds.dimensionless()
     )
@@ -483,7 +483,7 @@ Foam::dimensionSet Foam::inv(const dimensionSet& ds)
 
 Foam::dimensionSet Foam::trans(const dimensionSet& ds)
 {
-    if (dimensionSet::debug && !ds.dimensionless())
+    if (dimensionSet::checking() && !ds.dimensionless())
     {
         FatalErrorInFunction
             << "Argument of trancendental function not dimensionless" << nl
@@ -496,7 +496,7 @@ Foam::dimensionSet Foam::trans(const dimensionSet& ds)
 
 Foam::dimensionSet Foam::atan2(const dimensionSet& ds1, const dimensionSet& ds2)
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("atan2(a, b)", ds1, ds2);
     }
@@ -507,7 +507,7 @@ Foam::dimensionSet Foam::atan2(const dimensionSet& ds1, const dimensionSet& ds2)
 
 Foam::dimensionSet Foam::hypot(const dimensionSet& ds1, const dimensionSet& ds2)
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("hypot(a, b)", ds1, ds2);
     }
@@ -548,7 +548,7 @@ Foam::dimensionSet Foam::operator+
     const dimensionSet& ds2
 )
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("(a + b)", ds1, ds2);
     }
@@ -563,7 +563,7 @@ Foam::dimensionSet Foam::operator-
     const dimensionSet& ds2
 )
 {
-    if (dimensionSet::debug)
+    if (dimensionSet::checking())
     {
         checkDims("(a - b)", ds1, ds2);
     }
diff --git a/src/OpenFOAM/dimensionSet/dimensionSet.H b/src/OpenFOAM/dimensionSet/dimensionSet.H
index 5302423634..34c3c00be8 100644
--- a/src/OpenFOAM/dimensionSet/dimensionSet.H
+++ b/src/OpenFOAM/dimensionSet/dimensionSet.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2017-2019 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -54,7 +54,7 @@ SourceFiles
 namespace Foam
 {
 
-// Forward declarations
+// Forward Declarations
 
 class dimensionSet;
 class dimensionSets;
@@ -97,17 +97,17 @@ public:
 
 private:
 
-    // Private data
+    // Private Data
 
         //- The array of dimension exponents
         list_type exponents_;
 
 
-    // Private classes
+    // Private Classes
 
         class tokeniser
         {
-            // Private data
+            // Private Data
 
                 Istream& is_;
 
@@ -171,6 +171,24 @@ public:
     ClassName("dimensionSet");
 
 
+    // Static Functions
+
+        //- Turn dimension checking on/off.
+        //  \return the previous value
+        static bool checking(const bool on) noexcept
+        {
+            bool old(debug);
+            debug = static_cast<int>(on);
+            return old;
+        }
+
+        //- True if dimension checking is enabled (the usual default)
+        static bool checking() noexcept
+        {
+            return static_cast<bool>(debug);
+        }
+
+
     // Constructors
 
         //- Default construct (dimensionless).
diff --git a/src/OpenFOAM/dimensionedTypes/dimensionedMinMax/dimensionedMinMax.H b/src/OpenFOAM/dimensionedTypes/dimensionedMinMax/dimensionedMinMax.H
index 3b4a7a069b..5a6446d534 100644
--- a/src/OpenFOAM/dimensionedTypes/dimensionedMinMax/dimensionedMinMax.H
+++ b/src/OpenFOAM/dimensionedTypes/dimensionedMinMax/dimensionedMinMax.H
@@ -100,7 +100,7 @@ inline dimensioned<MinMax<T>> makeDimensionedMinMax
     const dimensioned<T>& maxVal
 )
 {
-    // Dimension check when (dimensionSet::debug)
+    // Dimension check when dimensionSet::checking()
     return dimensioned<MinMax<T>>
     (
         name,
diff --git a/src/finiteArea/faMatrices/faMatrix/faMatrix.C b/src/finiteArea/faMatrices/faMatrix/faMatrix.C
index be37b965ac..01cd2e8812 100644
--- a/src/finiteArea/faMatrices/faMatrix/faMatrix.C
+++ b/src/finiteArea/faMatrices/faMatrix/faMatrix.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -1049,7 +1049,11 @@ void Foam::checkMethod
             << abort(FatalError);
     }
 
-    if (dimensionSet::debug && fam1.dimensions() != fam2.dimensions())
+    if
+    (
+        dimensionSet::checking()
+     && fam1.dimensions() != fam2.dimensions()
+    )
     {
         FatalErrorInFunction
             << "incompatible dimensions for operation "
@@ -1070,7 +1074,11 @@ void Foam::checkMethod
     const char* op
 )
 {
-    if (dimensionSet::debug && fam.dimensions()/dimArea != vf.dimensions())
+    if
+    (
+        dimensionSet::checking()
+     && fam.dimensions()/dimArea != vf.dimensions()
+    )
     {
         FatalErrorInFunction
             <<  "incompatible dimensions for operation "
@@ -1091,7 +1099,11 @@ void Foam::checkMethod
     const char* op
 )
 {
-    if (dimensionSet::debug && fam.dimensions()/dimArea != dt.dimensions())
+    if
+    (
+        dimensionSet::checking()
+     && fam.dimensions()/dimArea != dt.dimensions()
+    )
     {
         FatalErrorInFunction
             << "incompatible dimensions for operation "
diff --git a/src/finiteVolume/expressions/base/fvExprDriverTemplates.C b/src/finiteVolume/expressions/base/fvExprDriverTemplates.C
index dc00ffebce..f77d251b87 100644
--- a/src/finiteVolume/expressions/base/fvExprDriverTemplates.C
+++ b/src/finiteVolume/expressions/base/fvExprDriverTemplates.C
@@ -405,8 +405,7 @@ Foam::tmp<GeomField> Foam::expressions::fvExprDriver::getOrReadFieldImpl
             }
 
             // Switch dimension checking off
-            const int oldDebug = dimensionSet::debug;
-            dimensionSet::debug = 0;
+            const bool oldDimChecking = dimensionSet::checking(false);
 
             // go through ALL old times
             GeomField* fp = &(fld);
@@ -418,7 +417,7 @@ Foam::tmp<GeomField> Foam::expressions::fvExprDriver::getOrReadFieldImpl
             }
 
             // Restore old value of dimension checking
-            dimensionSet::debug = oldDebug;
+            dimensionSet::checking(oldDimChecking);
         }
     }
     else if (mandatory)
diff --git a/src/finiteVolume/fvMatrices/fvMatrix/fvMatrix.C b/src/finiteVolume/fvMatrices/fvMatrix/fvMatrix.C
index 1aa4aa9ffb..96b3ff6c9f 100644
--- a/src/finiteVolume/fvMatrices/fvMatrix/fvMatrix.C
+++ b/src/finiteVolume/fvMatrices/fvMatrix/fvMatrix.C
@@ -1992,7 +1992,11 @@ void Foam::checkMethod
             << abort(FatalError);
     }
 
-    if (dimensionSet::debug && fvm1.dimensions() != fvm2.dimensions())
+    if
+    (
+        dimensionSet::checking()
+     && fvm1.dimensions() != fvm2.dimensions()
+    )
     {
         FatalErrorInFunction
             << "incompatible dimensions for operation "
@@ -2013,7 +2017,11 @@ void Foam::checkMethod
     const char* op
 )
 {
-    if (dimensionSet::debug && fvm.dimensions()/dimVolume != df.dimensions())
+    if
+    (
+        dimensionSet::checking()
+     && fvm.dimensions()/dimVolume != df.dimensions()
+    )
     {
         FatalErrorInFunction
             << endl << "    "
@@ -2033,7 +2041,11 @@ void Foam::checkMethod
     const char* op
 )
 {
-    if (dimensionSet::debug && fvm.dimensions()/dimVolume != dt.dimensions())
+    if
+    (
+        dimensionSet::checking()
+     && fvm.dimensions()/dimVolume != dt.dimensions()
+    )
     {
         FatalErrorInFunction
             << "incompatible dimensions for operation "
diff --git a/src/functionObjects/field/log/log.C b/src/functionObjects/field/log/log.C
index 70ff35eace..7ebdb96def 100644
--- a/src/functionObjects/field/log/log.C
+++ b/src/functionObjects/field/log/log.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2018-2019 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 ------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -50,13 +50,12 @@ bool Foam::functionObjects::log::calc()
     {
         const volScalarField& x = lookupObject<volScalarField>(fieldName_);
 
-        // Cache the current debug setting for dimensionSet
-        const bool dimensionSetDebug = dimensionSet::debug;
-
         // Switch-off dimension checking if requested
+        const bool oldDimChecking = dimensionSet::checking();
+
         if (!checkDimensions_)
         {
-            dimensionSet::debug = 0;
+            dimensionSet::checking(false);
         }
 
         bool stored = store
@@ -68,7 +67,7 @@ bool Foam::functionObjects::log::calc()
         // Reinstate dimension checking
         if (!checkDimensions_)
         {
-            dimensionSet::debug = dimensionSetDebug;
+            dimensionSet::checking(oldDimChecking);
         }
 
         return stored;
diff --git a/src/functionObjects/field/pow/pow.C b/src/functionObjects/field/pow/pow.C
index 6315653f93..18a4c85a30 100644
--- a/src/functionObjects/field/pow/pow.C
+++ b/src/functionObjects/field/pow/pow.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 ------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -49,13 +49,12 @@ bool Foam::functionObjects::pow::calc()
     {
         const volScalarField& x = lookupObject<volScalarField>(fieldName_);
 
-        // Cache the current debug setting for dimensionSet
-        const bool dimensionSetDebug = dimensionSet::debug;
-
         // Switch-off dimension checking if requested
+        const bool oldDimChecking = dimensionSet::checking();
+
         if (!checkDimensions_)
         {
-            dimensionSet::debug = 0;
+            dimensionSet::checking(false);
         }
 
         bool stored = store
@@ -67,7 +66,7 @@ bool Foam::functionObjects::pow::calc()
         // Reinstate dimension checking
         if (!checkDimensions_)
         {
-            dimensionSet::debug = dimensionSetDebug;
+            dimensionSet::checking(oldDimChecking);
         }
 
         return stored;