diff --git a/Src/Extern/HDF5/AMReX_ParticleHDF5.H b/Src/Extern/HDF5/AMReX_ParticleHDF5.H
index a1b9d8faeb8..29747ea9d76 100644
--- a/Src/Extern/HDF5/AMReX_ParticleHDF5.H
+++ b/Src/Extern/HDF5/AMReX_ParticleHDF5.H
@@ -17,6 +17,8 @@
 #include "H5Z_SZ.h"
 #endif
 
+namespace amrex {
+
 template <typename ParticleType, int NArrayReal, int NArrayInt,
           template<class> class Allocator, class CellAssignor>
 void
@@ -1534,5 +1536,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     Gpu::streamSynchronize();
 }
 
+}
+
 #endif /*AMREX_USE_HDF5*/
 #endif /*AMREX_PARTICLEHDF5_H*/
diff --git a/Src/Extern/HDF5/AMReX_ParticleUtilHDF5.H b/Src/Extern/HDF5/AMReX_ParticleUtilHDF5.H
index 95f96900b00..aa2a30a3973 100644
--- a/Src/Extern/HDF5/AMReX_ParticleUtilHDF5.H
+++ b/Src/Extern/HDF5/AMReX_ParticleUtilHDF5.H
@@ -1,6 +1,8 @@
 #ifdef AMREX_USE_HDF5_ASYNC
 #include "hdf5.h"
 
+namespace amrex {
+
 hid_t es_par_g = 0;
 
 void async_vol_es_wait_particle()
@@ -29,4 +31,7 @@ void async_vol_es_wait_close_particle()
     }
     return;
 }
+
+}
+
 #endif
diff --git a/Src/Extern/HDF5/AMReX_WriteBinaryParticleDataHDF5.H b/Src/Extern/HDF5/AMReX_WriteBinaryParticleDataHDF5.H
index 462716ae2a3..f0e269c5f42 100644
--- a/Src/Extern/HDF5/AMReX_WriteBinaryParticleDataHDF5.H
+++ b/Src/Extern/HDF5/AMReX_WriteBinaryParticleDataHDF5.H
@@ -1,6 +1,8 @@
 #ifndef AMREX_WRITE_BINARY_PARTICLE_DATA_HDF5_H
 #define AMREX_WRITE_BINARY_PARTICLE_DATA_HDF5_H
 
+namespace amrex {
+
 static int CreateWriteHDF5Attr(hid_t loc, const char *name, hsize_t n, void *data, hid_t dtype)
 {
     herr_t ret;
@@ -476,4 +478,6 @@ void WriteHDF5ParticleDataSync (PC const& pc,
     return;
 } // End WriteHDF5ParticleDataSync
 
+}
+
 #endif /*AMREX_WRITE_BINARY_PARTICLE_DATA_HDF5_H*/
diff --git a/Src/Particle/AMReX_MakeParticle.H b/Src/Particle/AMReX_MakeParticle.H
index 5395b4443f5..f361a34727e 100644
--- a/Src/Particle/AMReX_MakeParticle.H
+++ b/Src/Particle/AMReX_MakeParticle.H
@@ -3,6 +3,8 @@
 
 #include <type_traits>
 
+namespace amrex {
+
 template< class T >
 struct is_soa_particle
      : std::integral_constant<
@@ -37,4 +39,6 @@ struct make_particle<T_ParticleType, std::enable_if_t<is_soa_particle<T_Particle
     }
 };
 
+}
+
 #endif
diff --git a/Src/Particle/AMReX_NeighborParticles.H b/Src/Particle/AMReX_NeighborParticles.H
index 9b3f01d4318..47dc17413fd 100644
--- a/Src/Particle/AMReX_NeighborParticles.H
+++ b/Src/Particle/AMReX_NeighborParticles.H
@@ -483,6 +483,8 @@ protected:
     bool m_has_neighbors = false;
 };
 
+}
+
 #include "AMReX_NeighborParticlesI.H"
 
 #ifdef AMREX_USE_GPU
@@ -491,6 +493,4 @@ protected:
 #include "AMReX_NeighborParticlesCPUImpl.H"
 #endif
 
-}
-
 #endif // _NEIGHBORPARTICLES_H_
diff --git a/Src/Particle/AMReX_NeighborParticlesCPUImpl.H b/Src/Particle/AMReX_NeighborParticlesCPUImpl.H
index 6f7da58f06e..c4d0b91c1ed 100644
--- a/Src/Particle/AMReX_NeighborParticlesCPUImpl.H
+++ b/Src/Particle/AMReX_NeighborParticlesCPUImpl.H
@@ -2,6 +2,8 @@
 #define AMREX_NEIGHBORPARTICLESCPUIMPL_H_
 #include <AMReX_Config.H>
 
+namespace amrex {
+
 template <int NStructReal, int NStructInt, int NArrayReal, int NArrayInt>
 void
 NeighborParticleContainer<NStructReal, NStructInt, NArrayReal, NArrayInt>
@@ -653,4 +655,6 @@ fillNeighborsMPI (bool reuse_rcv_counts) {
 #endif
 }
 
+}
+
 #endif
diff --git a/Src/Particle/AMReX_NeighborParticlesGPUImpl.H b/Src/Particle/AMReX_NeighborParticlesGPUImpl.H
index ce0444ac44d..5932063510c 100644
--- a/Src/Particle/AMReX_NeighborParticlesGPUImpl.H
+++ b/Src/Particle/AMReX_NeighborParticlesGPUImpl.H
@@ -2,6 +2,8 @@
 #define AMREX_NEIGHBORPARTICLESGPUIMPL_H_
 #include <AMReX_Config.H>
 
+namespace amrex {
+
 namespace detail
 {
     inline Vector<Box> getBoundaryBoxes(const Box& box, int ncells)
@@ -314,4 +316,6 @@ clearNeighborsGPU()
     }
 }
 
+}
+
 #endif
diff --git a/Src/Particle/AMReX_NeighborParticlesI.H b/Src/Particle/AMReX_NeighborParticlesI.H
index 8e5bb2b2563..de5146fbe9c 100644
--- a/Src/Particle/AMReX_NeighborParticlesI.H
+++ b/Src/Particle/AMReX_NeighborParticlesI.H
@@ -1,4 +1,6 @@
 
+namespace amrex {
+
 template <int NStructReal, int NStructInt, int NArrayReal, int NArrayInt>
 bool NeighborParticleContainer<NStructReal, NStructInt, NArrayReal, NArrayInt>::use_mask = false;
 
@@ -1127,3 +1129,5 @@ resizeContainers (int num_levels)
     AMREX_ASSERT((neighbors.size() == m_neighbor_list.size()) &&
                  (neighbors.size() == mask_ptr.size()     )    );
 }
+
+}
diff --git a/Src/Particle/AMReX_ParticleContainer.H b/Src/Particle/AMReX_ParticleContainer.H
index 82f05a11bd2..2543f0d3815 100644
--- a/Src/Particle/AMReX_ParticleContainer.H
+++ b/Src/Particle/AMReX_ParticleContainer.H
@@ -1529,6 +1529,7 @@ using ParticleContainer = ParticleContainer_impl<Particle<T_NStructReal, T_NStru
 template <int T_NArrayReal, int T_NArrayInt, template<class> class Allocator=DefaultAllocator, class CellAssignor=DefaultAssignor>
 using ParticleContainerPureSoA = ParticleContainer_impl<SoAParticle<T_NArrayReal, T_NArrayInt>, T_NArrayReal, T_NArrayInt, Allocator, CellAssignor>;
 
+}
 
 #include "AMReX_ParticleInit.H"
 #include "AMReX_ParticleContainerI.H"
@@ -1538,6 +1539,4 @@ using ParticleContainerPureSoA = ParticleContainer_impl<SoAParticle<T_NArrayReal
 #include "AMReX_ParticleHDF5.H"
 #endif
 
-}
-
 #endif /*_PARTICLES_H_*/
diff --git a/Src/Particle/AMReX_ParticleContainerI.H b/Src/Particle/AMReX_ParticleContainerI.H
index e87cda19d7e..03aa1f7aca0 100644
--- a/Src/Particle/AMReX_ParticleContainerI.H
+++ b/Src/Particle/AMReX_ParticleContainerI.H
@@ -8,6 +8,7 @@
 #include <type_traits>
 #include <vector>
 
+namespace amrex {
 
 template <typename ParticleType, int NArrayReal, int NArrayInt,
           template<class> class Allocator, class CellAssignor>
@@ -2668,3 +2669,5 @@ ResizeRuntimeIntComp (int new_size, bool communicate)
         }
     }
 }
+
+}
diff --git a/Src/Particle/AMReX_ParticleIO.H b/Src/Particle/AMReX_ParticleIO.H
index dd390309f22..f91f38f7612 100644
--- a/Src/Particle/AMReX_ParticleIO.H
+++ b/Src/Particle/AMReX_ParticleIO.H
@@ -4,6 +4,8 @@
 
 #include <AMReX_WriteBinaryParticleData.H>
 
+namespace amrex {
+
 template <typename ParticleType, int NArrayReal, int NArrayInt,
           template<class> class Allocator, class CellAssignor>
 void
@@ -1274,4 +1276,6 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     }
 }
 
+}
+
 #endif /*AMREX_PARTICLEIO_H*/
diff --git a/Src/Particle/AMReX_ParticleInit.H b/Src/Particle/AMReX_ParticleInit.H
index 9fee3729ab6..508877bb07b 100644
--- a/Src/Particle/AMReX_ParticleInit.H
+++ b/Src/Particle/AMReX_ParticleInit.H
@@ -2,6 +2,8 @@
 #define AMREX_PARTICLEINIT_H
 #include <AMReX_Config.H>
 
+namespace amrex {
+
 /*
   \brief Initialize particles from an Ascii file in the following format:
 
@@ -1683,4 +1685,7 @@ InitNRandomPerCell (int n_per_cell, const ParticleInitData& pdata)
 
     Gpu::streamSynchronize();
 }
+
+}
+
 #endif /*AMREX_PARTICLEINIT_H*/
diff --git a/Src/Particle/AMReX_ParticleUtil.cpp b/Src/Particle/AMReX_ParticleUtil.cpp
index 63d0cbe90db..41538dab317 100644
--- a/Src/Particle/AMReX_ParticleUtil.cpp
+++ b/Src/Particle/AMReX_ParticleUtil.cpp
@@ -64,8 +64,8 @@ Vector<int> computeNeighborProcs (const ParGDBBase* a_gdb, int ngrow)
     RemoveDuplicates(neighbor_procs);
     return neighbor_procs;
 }
+}
 
 #ifdef AMREX_USE_HDF5_ASYNC
 #include "AMReX_ParticleUtilHDF5.H"
 #endif
-}
diff --git a/Src/Particle/AMReX_WriteBinaryParticleData.H b/Src/Particle/AMReX_WriteBinaryParticleData.H
index 20aebe9c6d3..fb7366aca68 100644
--- a/Src/Particle/AMReX_WriteBinaryParticleData.H
+++ b/Src/Particle/AMReX_WriteBinaryParticleData.H
@@ -6,6 +6,10 @@
 #include <AMReX_ParticleUtil.H>
 #include <AMReX_GpuDevice.H>
 
+namespace amrex {
+
+namespace {
+
 struct KeepValidFilter
 {
     template <typename SrcData>
@@ -1158,6 +1162,9 @@ void WriteBinaryParticleDataAsync (PC const& pc,
     });
 }
 
+}
+}
+
 #ifdef AMREX_USE_HDF5
 #include <AMReX_WriteBinaryParticleDataHDF5.H>
 #endif