diff --git a/src/api.F90 b/src/api.F90
index 2c1fc968b..b767d1ab4 100644
--- a/src/api.F90
+++ b/src/api.F90
@@ -92,11 +92,11 @@ contains
     integer(C_INT32_T), optional, intent(in) :: instance
     integer(C_INT) :: err
 
-    integer :: i, n
+    integer :: n
 
     err = E_UNASSIGNED
     if (index >= 1 .and. index <= size(cells)) then
-      associate (c => cells(i))
+      associate (c => cells(index))
         if (allocated(c % sqrtkT)) then
           n = size(c % sqrtkT)
           if (present(instance) .and. n > 1) then
@@ -122,7 +122,7 @@ contains
 
   subroutine openmc_finalize() bind(C)
 
-    integer :: hdf5_err
+    integer :: err
 
     ! Clear results
     call openmc_reset()
@@ -190,14 +190,14 @@ contains
     call free_memory()
 
     ! Release compound datatypes
-    call h5tclose_f(hdf5_bank_t, hdf5_err)
+    call h5tclose_f(hdf5_bank_t, err)
 
     ! Close FORTRAN interface.
-    call h5close_f(hdf5_err)
+    call h5close_f(err)
 
 #ifdef MPI
     ! Free all MPI types
-    call MPI_TYPE_FREE(MPI_BANK, mpi_err)
+    call MPI_TYPE_FREE(MPI_BANK, err)
 #endif
 
   end subroutine openmc_finalize
diff --git a/src/cmfd_execute.F90 b/src/cmfd_execute.F90
index 0d4a9f4d3..e87bff930 100644
--- a/src/cmfd_execute.F90
+++ b/src/cmfd_execute.F90
@@ -108,6 +108,9 @@ contains
     real(8) :: hxyz(3) ! cell dimensions of current ijk cell
     real(8) :: vol     ! volume of cell
     real(8),allocatable :: source(:,:,:,:)  ! tmp source array for entropy
+#ifdef MPI
+    integer :: mpi_err ! MPI error code
+#endif
 
     ! Get maximum of spatial and group indices
     nx = cmfd % indices(1)
@@ -232,6 +235,9 @@ contains
     logical :: outside  ! any source sites outside mesh
     logical :: in_mesh  ! source site is inside mesh
     type(RegularMesh), pointer :: m ! point to mesh
+#ifdef MPI
+    integer :: mpi_err
+#endif
 
     ! Associate pointer
     m => meshes(n_user_meshes + 1)
diff --git a/src/eigenvalue.F90 b/src/eigenvalue.F90
index 9f4da7c82..accf80b31 100644
--- a/src/eigenvalue.F90
+++ b/src/eigenvalue.F90
@@ -40,6 +40,7 @@ contains
          & temp_sites(:)       ! local array of extra sites on each node
 
 #ifdef MPI
+    integer    :: mpi_err      ! MPI error code
     integer(8) :: n            ! number of sites to send/recv
     integer    :: neighbor     ! processor to send/recv data from
 #ifdef MPIF08
@@ -372,6 +373,9 @@ contains
   subroutine calculate_generation_keff()
 
     integer :: i  ! overall generation
+#ifdef MPI
+    integer :: mpi_err ! MPI error code
+#endif
 
     ! Get keff for this generation by subtracting off the starting value
     keff_generation = global_tallies(RESULT_VALUE, K_TRACKLENGTH) - keff_generation
@@ -614,6 +618,7 @@ contains
     logical :: sites_outside ! were there sites outside the ufs mesh?
 #ifdef MPI
     integer :: n             ! total number of ufs mesh cells
+    integer :: mpi_err       ! MPI error code
 #endif
 
     if (current_batch == 1 .and. current_gen == 1) then
diff --git a/src/initialize.F90 b/src/initialize.F90
index 69479907e..1e29c638c 100644
--- a/src/initialize.F90
+++ b/src/initialize.F90
@@ -172,6 +172,7 @@ contains
     integer, intent(in) :: intracomm         ! MPI intracommunicator
 #endif
 
+    integer                   :: mpi_err          ! MPI error code
     integer                   :: bank_blocks(5)   ! Count for each datatype
 #ifdef MPIF08
     type(MPI_Datatype)        :: bank_types(5)
diff --git a/src/main.F90 b/src/main.F90
index b8c96927e..fadf9f3bb 100644
--- a/src/main.F90
+++ b/src/main.F90
@@ -9,6 +9,10 @@ program main
 
   implicit none
 
+#ifdef MPI
+  integer :: mpi_err ! MPI error code
+#endif
+
   ! Initialize run -- when run with MPI, pass communicator
 #ifdef MPI
 #ifdef MPIF08
diff --git a/src/mesh.F90 b/src/mesh.F90
index 427710790..c25e3f7a6 100644
--- a/src/mesh.F90
+++ b/src/mesh.F90
@@ -144,6 +144,9 @@ contains
     integer :: ijk(3)   ! indices on mesh
     integer :: n        ! number of energy groups / size
     integer :: e_bin    ! energy_bin
+#ifdef MPI
+    integer :: mpi_err  ! MPI error code
+#endif
     logical :: in_mesh  ! was single site outside mesh?
     logical :: outside  ! was any site outside mesh?
 
diff --git a/src/message_passing.F90 b/src/message_passing.F90
index 6c13b00e8..0f2b94d1a 100644
--- a/src/message_passing.F90
+++ b/src/message_passing.F90
@@ -16,7 +16,6 @@ module message_passing
   integer :: rank        = 0       ! rank of process
   logical :: master      = .true.  ! master process?
   logical :: mpi_enabled = .false. ! is MPI in use and initialized?
-  integer :: mpi_err               ! MPI error code
 #ifdef MPIF08
   type(MPI_Datatype) :: MPI_BANK   ! MPI datatype for fission bank
   type(MPI_Comm) :: mpi_intracomm  ! MPI intra-communicator
diff --git a/src/simulation.F90 b/src/simulation.F90
index 8a32493ca..b406679ce 100644
--- a/src/simulation.F90
+++ b/src/simulation.F90
@@ -285,6 +285,10 @@ contains
 
   subroutine finalize_batch()
 
+#ifdef MPI
+    integer :: mpi_err ! MPI error code
+#endif
+
     ! Reduce tallies onto master process and accumulate
     call time_tallies % start()
     call accumulate_tallies()
@@ -392,7 +396,11 @@ contains
 
     integer :: i       ! loop index for tallies
     integer :: n       ! size of arrays
-    real(8) :: temp(3) ! temporary array for communication
+#ifdef MPI
+    integer    :: mpi_err  ! MPI error code
+    integer(8) :: temp
+    real(8)    :: tempr(3) ! temporary array for communication
+#endif
 
 !$omp parallel
     deallocate(micro_xs)
@@ -420,18 +428,23 @@ contains
 
     ! These guys are needed so that non-master processes can calculate the
     ! combined estimate of k-effective
-    temp(1) = k_col_abs
-    temp(2) = k_col_tra
-    temp(3) = k_abs_tra
-    call MPI_BCAST(temp, 3, MPI_REAL8, 0, mpi_intracomm, mpi_err)
-    k_col_abs = temp(1)
-    k_col_tra = temp(2)
-    k_abs_tra = temp(3)
+    tempr(1) = k_col_abs
+    tempr(2) = k_col_tra
+    tempr(3) = k_abs_tra
+    call MPI_BCAST(tempr, 3, MPI_REAL8, 0, mpi_intracomm, mpi_err)
+    k_col_abs = tempr(1)
+    k_col_tra = tempr(2)
+    k_abs_tra = tempr(3)
+
+    if (check_overlaps) then
+      call MPI_REDUCE(overlap_check_cnt, temp, n_cells, MPI_INTEGER8, &
+           MPI_SUM, 0, mpi_intracomm, mpi_err)
+      overlap_check_cnt = temp
+    end if
 #endif
 
     ! Write tally results to tallies.out
     if (output_tallies .and. master) call write_tallies()
-    if (check_overlaps) call reduce_overlap_count()
 
     ! Stop timers and show timing statistics
     call time_finalize%stop()
@@ -444,20 +457,4 @@ contains
 
   end subroutine finalize_simulation
 
-!===============================================================================
-! REDUCE_OVERLAP_COUNT accumulates cell overlap check counts to master
-!===============================================================================
-
-  subroutine reduce_overlap_count()
-
-    integer(8) :: temp
-
-#ifdef MPI
-    call MPI_REDUCE(overlap_check_cnt, temp, n_cells, MPI_INTEGER8, &
-         MPI_SUM, 0, mpi_intracomm, mpi_err)
-    overlap_check_cnt = temp
-#endif
-
-  end subroutine reduce_overlap_count
-
 end module simulation
diff --git a/src/state_point.F90 b/src/state_point.F90
index 301a4efdd..e2a476e7e 100644
--- a/src/state_point.F90
+++ b/src/state_point.F90
@@ -522,7 +522,8 @@ contains
     real(8), allocatable :: tally_temp(:,:,:) ! contiguous array of results
     real(8), target :: global_temp(3,N_GLOBAL_TALLIES)
 #ifdef MPI
-    real(8) :: dummy  ! temporary receive buffer for non-root reduces
+    integer :: mpi_err ! MPI error code
+    real(8) :: dummy   ! temporary receive buffer for non-root reduces
 #endif
     type(TallyObject) :: dummy_tally
 
@@ -841,6 +842,7 @@ contains
 #else
     integer :: i
 #ifdef MPI
+    integer :: mpi_err ! MPI error code
     type(Bank), allocatable, target :: temp_source(:)
 #endif
 #endif
diff --git a/src/tally.F90 b/src/tally.F90
index 8b52ad032..cf62412f0 100644
--- a/src/tally.F90
+++ b/src/tally.F90
@@ -4246,9 +4246,10 @@ contains
   subroutine reduce_tally_results()
 
     integer :: i
-    integer :: n      ! number of filter bins
-    integer :: m      ! number of score bins
-    integer :: n_bins ! total number of bins
+    integer :: n       ! number of filter bins
+    integer :: m       ! number of score bins
+    integer :: n_bins  ! total number of bins
+    integer :: mpi_err ! MPI error code
     real(C_DOUBLE), allocatable :: tally_temp(:,:)  ! contiguous array of results
     real(C_DOUBLE), allocatable :: tally_temp2(:,:) ! reduced contiguous results
     real(C_DOUBLE) :: temp(N_GLOBAL_TALLIES), temp2(N_GLOBAL_TALLIES)
diff --git a/src/volume_calc.F90 b/src/volume_calc.F90
index 3659293b3..f8cf4085a 100644
--- a/src/volume_calc.F90
+++ b/src/volume_calc.F90
@@ -132,6 +132,7 @@ contains
     integer :: min_samples ! minimum number of samples per process
     integer :: remainder   ! leftover samples from uneven divide
 #ifdef MPI
+    integer :: mpi_err ! MPI error code
     integer :: m  ! index over materials
     integer :: n  ! number of materials
     integer, allocatable :: data(:) ! array used to send number of hits