From 2c45a28edd5afbf3b5c0755c703f41c76c4a6ef9 Mon Sep 17 00:00:00 2001
From: Jason Floyd <drjfloyd@gmail.com>
Date: Mon, 9 Mar 2026 15:00:29 -0400
Subject: [PATCH 1/6] FDS Docs: Fix spelling error

---
 Manuals/Bibliography/authors.tex | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Manuals/Bibliography/authors.tex b/Manuals/Bibliography/authors.tex
index 1d4baa892c9..7ad5b8fb913 100644
--- a/Manuals/Bibliography/authors.tex
+++ b/Manuals/Bibliography/authors.tex
@@ -61,7 +61,7 @@ \chapter{About the Developers}
 
 \item[Simo Hostikka] is an associate professor of fire safety engineering at Aalto University School of Engineering, since January 2014. Before joining Aalto, he worked as a Principal Scientist and Team Leader at VTT Technical Research Centre of Finland. He received a master of science (technology) degree in 1997 and a doctorate in 2008 from the Department of Engineering Physics and Mathematics of the Helsinki University of Technology.  He is the principal developer of the radiation and solid phase sub-models within FDS.
 
-\item[Jason Floyd] is a Principle Research Engineer at the UL Research Institutes' Fire Safety Research Institute in Columbia, Maryland. He received a B.S. (1993), M.S (1995), and a Ph.D. (2000) from the Nuclear Engineering Program of the University of Maryland. After graduating, he was awarded a National Research Council Post-Doctoral Fellowship at the Building and Fire Research Laboratory of NIST. He is a principal developer of the combustion, control logic, aerosol, droplet evaporation, and HVAC sub-models within FDS.
+\item[Jason Floyd] is a Principal Research Engineer at the UL Research Institutes' Fire Safety Research Institute in Columbia, Maryland. He received a B.S. (1993), M.S (1995), and a Ph.D. (2000) from the Nuclear Engineering Program of the University of Maryland. After graduating, he was awarded a National Research Council Post-Doctoral Fellowship at the Building and Fire Research Laboratory of NIST. He is a principal developer of the combustion, control logic, aerosol, droplet evaporation, and HVAC sub-models within FDS.
 
 \item[Randall McDermott] joined the Fire Research Division at NIST in 2008. He received a B.S.~from the University of Tulsa in Chemical Engineering in 1994 and a Ph.D.~from the University of Utah in 2005. His research interests include subgrid-scale models and numerical methods for large-eddy simulation, turbulent combustion, immersed boundary methods, and Lagrangian particle methods.
 

From 61bd9cc6317ea4f47f46de3d52268e858f0ca8b0 Mon Sep 17 00:00:00 2001
From: mcgratta <mcgratta@gmail.com>
Date: Mon, 9 Mar 2026 15:22:22 -0400
Subject: [PATCH 2/6] FDS Source: Add PRIVATE attribute to some modules

---
 Source/chem.f90 | 3 ++-
 Source/ctrl.f90 | 3 +++
 Source/hvac.f90 | 3 ++-
 Source/init.f90 | 1 -
 Source/main.f90 | 4 ++++
 Source/pois.f90 | 8 +++-----
 Source/prop.f90 | 4 +++-
 Source/radi.f90 | 1 +
 Source/rcal.f90 | 3 ++-
 Source/read.f90 | 1 -
 Source/soot.f90 | 4 ++--
 11 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/Source/chem.f90 b/Source/chem.f90
index d7d2cc2d327..2cf2f37c52c 100644
--- a/Source/chem.f90
+++ b/Source/chem.f90
@@ -18,6 +18,7 @@ MODULE CVODE_INTERFACE
 USE FSUNDIALS_CORE_MOD
 
 IMPLICIT NONE
+PRIVATE
 
 TYPE :: USERDATA
     REAL(EB) :: ZETA0 ! initial unmixed fraction
@@ -29,7 +30,7 @@ MODULE CVODE_INTERFACE
 
 LOGICAL :: DEBUG=.FALSE.
 REAL(EB), PARAMETER :: MIN_CHEM_TMP=200._EB
-REAL(EB) :: CUR_CFD_TIME
+REAL(EB), PUBLIC :: CUR_CFD_TIME
 
 PUBLIC CVODE_SERIAL
 
diff --git a/Source/ctrl.f90 b/Source/ctrl.f90
index 1c35864927b..4d7d648a0d9 100644
--- a/Source/ctrl.f90
+++ b/Source/ctrl.f90
@@ -8,6 +8,9 @@ MODULE CONTROL_FUNCTIONS
 USE DEVICE_VARIABLES
 
 IMPLICIT NONE (TYPE,EXTERNAL)
+PRIVATE
+
+PUBLIC UPDATE_CONTROLS,EVALUATE_CONTROL
 
 CONTAINS
 
diff --git a/Source/hvac.f90 b/Source/hvac.f90
index 9cd4bb7eaae..6bf7ba5b545 100644
--- a/Source/hvac.f90
+++ b/Source/hvac.f90
@@ -5069,8 +5069,9 @@ END SUBROUTINE HVAC_UPDATE_QFAN
 !> \brief Define the index and other properties of output quantities
 
 SUBROUTINE GET_QUANTITY_INDEX(SMOKEVIEW_LABEL,SMOKEVIEW_BAR_LABEL,OUTPUT_INDEX,Y_INDEX,Z_INDEX,UNITS,QUANTITY,SPEC_ID)
+
 USE MISC_FUNCTIONS, ONLY: GET_SPEC_OR_SMIX_INDEX
-USE OUTPUT_DATA
+USE OUTPUT_DATA, ONLY: OUTPUT_QUANTITY
 CHARACTER(*), INTENT(INOUT) :: QUANTITY
 CHARACTER(*), INTENT(OUT) :: SMOKEVIEW_LABEL,SMOKEVIEW_BAR_LABEL,UNITS
 CHARACTER(*), INTENT(IN) :: SPEC_ID
diff --git a/Source/init.f90 b/Source/init.f90
index f53548cbd9e..46912a85a91 100644
--- a/Source/init.f90
+++ b/Source/init.f90
@@ -11,7 +11,6 @@ MODULE INIT
 USE DEVICE_VARIABLES
 
 IMPLICIT NONE (TYPE,EXTERNAL)
-
 PRIVATE
 
 PUBLIC INITIALIZE_WALL_ARRAY,INITIALIZE_ATMOSPHERE,INITIALIZE_MESH_VARIABLES_1,INITIALIZE_MESH_VARIABLES_2,&
diff --git a/Source/main.f90 b/Source/main.f90
index 0836cd4fa4c..b848925a628 100644
--- a/Source/main.f90
+++ b/Source/main.f90
@@ -1073,6 +1073,7 @@ END SUBROUTINE CHECK_MPI
 
 SUBROUTINE MPI_INITIALIZATION_CHORES(TASK_NUMBER)
 
+USE CONTROL_VARIABLES, ONLY: N_CTRL
 INTEGER, INTENT(IN) :: TASK_NUMBER
 TYPE (MPI_REQUEST), ALLOCATABLE, DIMENSION(:) :: REQ0,REQ0DUM
 TYPE (MPI_GROUP) :: GROUP_WORLD,SUBGROUP
@@ -3794,6 +3795,7 @@ END SUBROUTINE DUMP_TIMERS
 
 SUBROUTINE WRITE_STRINGS
 
+USE CONTROL_VARIABLES, ONLY: CONTROL
 INTEGER :: N,NOM,N_STRINGS_DUM
 CHARACTER(:), ALLOCATABLE :: STRING_BUF
 CHARACTER(MESH_STRING_LENGTH), ALLOCATABLE, DIMENSION(:) :: STRING_DUM
@@ -4213,6 +4215,7 @@ END SUBROUTINE EXCHANGE_GLOBAL_OUTPUTS
 
 SUBROUTINE DUMP_GLOBAL_OUTPUTS
 
+USE CONTROL_VARIABLES, ONLY: N_CTRL,CONTROL
 REAL(EB) :: TNOW
 TYPE(DEVICE_TYPE), POINTER :: DV
 
@@ -4394,6 +4397,7 @@ END SUBROUTINE EXCHANGE_HVAC_SOLUTION
 
 SUBROUTINE EXCHANGE_EXTERNAL
 
+USE CONTROL_VARIABLES, ONLY: N_CTRL
 REAL(EB) :: TNOW
 
 TNOW = CURRENT_TIME()
diff --git a/Source/pois.f90 b/Source/pois.f90
index 8de04679949..9f435f60f5d 100644
--- a/Source/pois.f90
+++ b/Source/pois.f90
@@ -1,13 +1,11 @@
-MODULE POIS
-
-! CODE CONVERTED USING TO_F90 BY ALAN MILLER
-! DATE: 2006-01-18  TIME: 13:48:46
+!> \brief Fast-Fourier transfer (FFT) Poisson pressure solver, Crayfishpak
 
-! POISSON SOLVER ROUTINES
+MODULE POIS
 
 USE PRECISION_PARAMETERS
 IMPLICIT NONE (TYPE,EXTERNAL)
 PRIVATE
+
 REAL(EB) SCALE
 INTEGER :: KAPPA,NMAX,IKPWR
 LOGICAL :: TPOSE,NOCOPY,OUTARY
diff --git a/Source/prop.f90 b/Source/prop.f90
index 0b6fd4d28e7..bd71beb0994 100644
--- a/Source/prop.f90
+++ b/Source/prop.f90
@@ -1,6 +1,7 @@
 !>brief Predefined gas and liquid thermophysical properties
 
 MODULE THERMO_PROPS
+
 USE PRECISION_PARAMETERS
 IMPLICIT NONE
 
@@ -7596,6 +7597,7 @@ END SUBROUTINE DEFINE_THERMO_PROPS
 
 END MODULE THERMO_PROPS
 
+
 MODULE QREF_DATA
 USE PRECISION_PARAMETERS
 IMPLICIT NONE
@@ -8930,4 +8932,4 @@ SUBROUTINE DEFINE_QREF_ARRAYS
 END SUBROUTINE DEFINE_QREF_ARRAYS   
 
 END MODULE QREF_DATA
-   
\ No newline at end of file
+   
diff --git a/Source/radi.f90 b/Source/radi.f90
index dd0bbfb31ca..093fe41cbb9 100644
--- a/Source/radi.f90
+++ b/Source/radi.f90
@@ -2749,6 +2749,7 @@ MODULE RAD
 USE MESH_POINTERS
 USE MESH_VARIABLES
 USE RADCONS
+USE RADCAL_VAR
 
 IMPLICIT NONE (TYPE,EXTERNAL)
 PRIVATE
diff --git a/Source/rcal.f90 b/Source/rcal.f90
index fb9d9924526..e6f085aa3a7 100644
--- a/Source/rcal.f90
+++ b/Source/rcal.f90
@@ -191,8 +191,9 @@ MODULE RADCAL_CALC
 USE RADCAL_VAR
 
 IMPLICIT NONE (TYPE,EXTERNAL)
+PRIVATE
 
-PUBLIC INIT_RADCAL,RCALLOC,RCDEALLOC,PLANCK,SUB_RADCAL
+PUBLIC INIT_RADCAL,RCALLOC,RCDEALLOC,RCDEALLOC2,PLANCK,SUB_RADCAL
 
 CONTAINS
 
diff --git a/Source/read.f90 b/Source/read.f90
index 331dfd1743e..4144f103acb 100644
--- a/Source/read.f90
+++ b/Source/read.f90
@@ -16868,7 +16868,6 @@ END SUBROUTINE GET_PROPERTY_INDEX
 
 SUBROUTINE READ_CSVF
 
-USE OUTPUT_DATA
 CHARACTER(FORMULA_LENGTH) :: SPECFILE,SPECFILE_BASE,SPECFILE_NM,TMPFILE,TMPFILE_BASE,TMPFILE_NM,UVWFILE,UVWFILE_BASE,UVWFILE_NM
 INTEGER :: N_CSVF,NM,STRLEN
 NAMELIST /CSVF/ SPECFILE,TMPFILE,UVWFILE
diff --git a/Source/soot.f90 b/Source/soot.f90
index cf87102abe0..769f76a7e4c 100644
--- a/Source/soot.f90
+++ b/Source/soot.f90
@@ -5,8 +5,9 @@ MODULE SOOT_ROUTINES
 USE GLOBAL_CONSTANTS, ONLY: N_PARTICLE_BINS, MIN_PARTICLE_DIAMETER, MAX_PARTICLE_DIAMETER, K_BOLTZMANN, &
                             N_TRACKED_SPECIES, GRAV, AGGLOMERATION_SMIX_INDEX, AGGLOMERATION_SPEC_INDEX, N_AGGLOMERATION_SPECIES
 IMPLICIT NONE (TYPE,EXTERNAL)
+PRIVATE
 
-PUBLIC CALC_AGGLOMERATION, INITIALIZE_AGGLOMERATION,SETTLING_VELOCITY,PARTICLE_RADIUS, SOOT_SURFACE_OXIDATION
+PUBLIC CALC_AGGLOMERATION,INITIALIZE_AGGLOMERATION,SETTLING_VELOCITY,PARTICLE_RADIUS,SOOT_SURFACE_OXIDATION,DROPLET_SCRUBBING
 
 REAL(EB) :: MIN_AGGLOMERATION=1.E-4_EB
 REAL(EB), ALLOCATABLE, DIMENSION(:) :: BIN_S
@@ -17,7 +18,6 @@ MODULE SOOT_ROUTINES
 TYPE(WALL_TYPE), POINTER :: WC
 TYPE(CFACE_TYPE), POINTER :: CFA
 TYPE(BOUNDARY_PROP1_TYPE), POINTER :: B1
-TYPE(BOUNDARY_PROP2_TYPE), POINTER :: B2
 TYPE(BOUNDARY_COORD_TYPE), POINTER :: BC
 
 CONTAINS

From 4ca61a542309f22a161c040896a503609c8e4b0d Mon Sep 17 00:00:00 2001
From: mcgratta <mcgratta@gmail.com>
Date: Tue, 10 Mar 2026 15:52:56 -0400
Subject: [PATCH 3/6] FDS Source: Clean up USE statements, add PRIVATE to
 modules

---
 Source/ccib.f90 |   3 +-
 Source/fire.f90 |   7 +--
 Source/geom.f90 |   3 +-
 Source/hvac.f90 | 152 +++++++++++++++++++++++++++++++++++-------------
 Source/main.f90 |   4 +-
 Source/turb.f90 |   2 +-
 6 files changed, 119 insertions(+), 52 deletions(-)

diff --git a/Source/ccib.f90 b/Source/ccib.f90
index a28a83b38a8..be466134231 100644
--- a/Source/ccib.f90
+++ b/Source/ccib.f90
@@ -15,6 +15,7 @@ MODULE CC_SCALARS
 USE MATH_FUNCTIONS, ONLY: GET_SCALAR_FACE_VALUE
 
 IMPLICIT NONE (TYPE,EXTERNAL)
+PRIVATE
 
 ! Debug Flags:
 LOGICAL, PARAMETER :: DEBUG_CC_INTERPOLATION=.FALSE. ! IBM interpolation and forcing scheme.
@@ -96,8 +97,6 @@ MODULE CC_SCALARS
 ! Baroclininc torque linking variables.
 REAL(EB), SAVE, ALLOCATABLE, DIMENSION(:) :: F_LINK,A_LINK
 
-PRIVATE
-
 PUBLIC :: ADD_CUTCELL_D_PBAR_DT, ADD_LINKEDCELL_D_PBAR_DT,ADD_CUTCELL_PSUM,ADD_LINKEDCELL_PSUM,&
           ADD_INPLACE_NNZ_H_WHLDOM,CALL_FOR_GLMAT,CALL_FROM_GLMAT_SETUP,&
           CCCOMPUTE_RADIATION,CC_DIVERGENCE_PART_1,CC_VEL_FACE_TO_SOLID_NODE,CC_BAROCLINIC_CORRECTION,&
diff --git a/Source/fire.f90 b/Source/fire.f90
index bac4f1bc540..9e8477fa49a 100644
--- a/Source/fire.f90
+++ b/Source/fire.f90
@@ -12,18 +12,14 @@ MODULE FIRE
 #endif
 
 IMPLICIT NONE (TYPE,EXTERNAL)
-
-
 PRIVATE
 
 REAL(EB), ALLOCATABLE, DIMENSION(:) :: DZ_F0
 REAL(EB) :: RRTMP0,MOLPCM3,T_CHEM_ODE, T_CHEM_COMM
-
-
 LOGICAL :: COMBUSTION_INIT=.FALSE.
-!INTEGER :: I0,J0,K0, NM0
 
 ! Variables needed for chemistry load distribution
+
 REAL(EB), ALLOCATABLE, DIMENSION(:,:) :: REALS_TO_SEND_ARRAY, REALS_TO_RECV_ARRAY, RESULTS_TO_SEND_ARRAY, &
                                        RESULTS_TO_RECV_ARRAY
 INTEGER, ALLOCATABLE, DIMENSION(:) :: NCELLS_TO_SEND_ARRAY, NCELLS_TO_RECV_ARRAY, SEND_DISPS, REVC_DISPS, &
@@ -32,7 +28,6 @@ MODULE FIRE
 INTEGER :: NVAR_TO_SEND
 INTEGER :: NVAR_TO_RECEIVE
 
-
 PUBLIC COMBUSTION_LOAD_BALANCED,COMBUSTION_BC,CONDENSATION_EVAPORATION,GET_FLAME_TEMPERATURE
 
 CONTAINS
diff --git a/Source/geom.f90 b/Source/geom.f90
index 66c7c892454..ef5b7996546 100644
--- a/Source/geom.f90
+++ b/Source/geom.f90
@@ -15,6 +15,8 @@ MODULE COMPLEX_GEOMETRY
 #endif /* WITH_MKL */
 
 IMPLICIT NONE (TYPE,EXTERNAL)
+PRIVATE
+
 CHARACTER(2*MESSAGE_LENGTH) :: MESSAGE
 
 !! ---------------------------------------------------------------------------------
@@ -311,7 +313,6 @@ MODULE COMPLEX_GEOMETRY
 ! End Variable declaration for CC_IBM.
 ! ---------------------------------------------------------------------------------
 
-PRIVATE
 PUBLIC :: BLOCK_CC_SOLID_EXTWALLCELLS,GEOFCT,CALL_FOR_GLMAT,CALL_FROM_GLMAT_SETUP,CCGUARD,CC_MATVEC_DEFINED,GEOMEPS,&
           DELTA_INT,DELTA_VERT,DEBUG_SET_CUTCELLS,DEBUG_WAIT,DIST_THRES,&
           GET_CARTCELL_CUTCELLS_TIME_INDEX,GET_CFACE_INDEX,GETU,&
diff --git a/Source/hvac.f90 b/Source/hvac.f90
index 6bf7ba5b545..62fbc016af3 100644
--- a/Source/hvac.f90
+++ b/Source/hvac.f90
@@ -7,7 +7,6 @@
 MODULE HVAC_ROUTINES
 
 USE PRECISION_PARAMETERS
-USE GLOBAL_CONSTANTS
 USE MESH_POINTERS
 USE DEVICE_VARIABLES
 USE CONTROL_VARIABLES
@@ -15,7 +14,6 @@ MODULE HVAC_ROUTINES
 USE MEMORY_FUNCTIONS, ONLY: ChkMemErr
 
 IMPLICIT NONE (TYPE,EXTERNAL)
-
 PRIVATE
 
 REAL(EB) :: DT_HV !< Size of subtimestep used in HVAC solver
@@ -74,6 +72,10 @@ MODULE HVAC_ROUTINES
 SUBROUTINE READ_HVAC
 
 USE MISC_FUNCTIONS, ONLY: SEARCH_CONTROLLER,GET_RAMP_INDEX
+USE GLOBAL_CONSTANTS, ONLY: LU_INPUT,INPUT_FILE_LINE_NUMBER,STOP_STATUS,SETUP_STOP,HVAC_DEBUG,N_DUCTS,N_DUCTNODES,&
+                            N_FILTERS,N_FANS,N_AIRCOILS,N_ZONE,N_SURF,HVAC_SOLVE,DUCT_NE,DUCT_DR,DUCTNODE_NE,DUCTNODE_DR,&
+                            RHOA,TMPA,N_TRACKED_SPECIES,T_BEGIN,TANH_RAMP,TSQR_RAMP,HVAC_MASS_TRANSPORT,XS_MIN,YS_MIN,ZS_MIN,&
+                            TMPM,NODE_Z_MIN,NODE_Z_MAX,T_USED,TAU_DEFAULT,HVAC_SOLVE,N_FANS,N_AIRCOILS
 INTEGER , PARAMETER :: MAX_DUCTS = 20 !< Maximum number of ducts connected to a node
 INTEGER :: IOS !< Used for returning the status of a READ statement
 INTEGER :: IZERO !< Used for returning the status of an ALLOCATE statement
@@ -831,6 +833,9 @@ END SUBROUTINE READ_HVAC
 SUBROUTINE PROC_HVAC
 
 USE PHYSICAL_FUNCTIONS, ONLY: GET_ENTHALPY
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,N_DUCTNODES,N_DUCTS,HVAC_SOLVE,N_FANS,N_AIRCOILS,N_LAGRANGIAN_CLASSES,RSUM0,&
+                            TMPA,RHOA,P_INF,NMESHES,PROCESS,MY_RANK,HVAC_SURF_INDEX,HVAC_BOUNDARY,PYROLYSIS_NONE,N_MPI_PROCESSES,&
+                            STOP_STATUS,N_FILTERS,T_USED
 USE MPI_F08
 INTEGER :: N,ND,ND2,NM,NN,NF,NV,IERR,NG,FI(3)
 REAL(EB) :: TNOW !< Current CPU time (s) used in computing length of time spent in HVAC routines.
@@ -1221,7 +1226,10 @@ END SUBROUTINE PROC_HVAC
 
 
 !< \brief Finds all connected ducts and nodes and hence number of ductruns
+
 SUBROUTINE CONNECTION_CHECK
+
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTNODES,N_CONNECTIVITY_INDICES,N_DUCTS
 INTEGER :: NN,NN3,ND
 LOGICAL :: NODE_CHECKED(N_DUCTNODES),NODE_CONNECTED(N_DUCTNODES)
 TYPE(DUCT_TYPE), POINTER :: DU
@@ -1298,8 +1306,11 @@ END SUBROUTINE CONNECTION_CHECK
 !> \brief Initializes duct node properties for non-leakage ducts
 
 SUBROUTINE INIT_DUCT_NODE
+
 USE PHYSICAL_FUNCTIONS, ONLY: GET_ENTHALPY
 USE MATH_FUNCTIONS, ONLY: EVALUATE_RAMP
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,N_DUCTNODES,STRATIFICATION,TMPA,I_RAMP_TMP0_Z,I_RAMP_P0_Z,RSUM0,P_INF,RHOA,N_INIT,&
+                            T_USED
 REAL(EB) :: ZZ_GET(1:N_TRACKED_SPECIES) !< Species mass fraction array.
 REAL(EB) :: VF(1:N_TRACKED_SPECIES) !< Species volunme fraction array.
 REAL(EB) :: TNOW !< Current CPU time (s) used in computing length of time spent in HVAC routines.
@@ -1368,6 +1379,9 @@ END SUBROUTINE INIT_DUCT_NODE
 !> \param FIRST_PASS Flag for the first call to the HVAC solver during a timestep, i.e. the first pressure iteration.
 
 SUBROUTINE HVAC_CALC(T,DT,FIRST_PASS)
+
+USE GLOBAL_CONSTANTS, ONLY: N_ZONE,N_DUCTS,CORRECTOR,OLD,NEW,N_DUCTNODES,HVAC_MASS_TRANSPORT,PREVIOUS,GUESS,HVAC_QFAN,P_INF,&
+                            N_NETWORKS,N_AIRCOILS,T_USED
 INTEGER :: NNE,NN,ND
 REAL(EB), INTENT(IN) :: T,DT
 REAL(EB) :: TNOW !< Current CPU time (s) used in computing length of time spent in HVAC routines.
@@ -1527,7 +1541,9 @@ END SUBROUTINE HVAC_CALC
 !> \param NNE Index indicating which HVAC network is being solved
 
 SUBROUTINE MATRIX_SOLVE(NNE)
-USE MATH_FUNCTIONS,ONLY : GAUSSJ
+
+USE MATH_FUNCTIONS, ONLY: GAUSSJ
+USE GLOBAL_CONSTANTS, ONLY: NEW
 INTEGER :: NNE,IERR,ND,NN
 REAL(EB), ALLOCATABLE, DIMENSION(:,:) :: LHS_GAUSSJ
 REAL(EB), ALLOCATABLE, DIMENSION(:) :: RHS_GAUSSJ
@@ -1568,6 +1584,7 @@ END SUBROUTINE MATRIX_SOLVE
 SUBROUTINE HVAC_UPDATE(NNE,DT)
 
 USE PHYSICAL_FUNCTIONS, ONLY : GET_SPECIFIC_GAS_CONSTANT,GET_ENTHALPY,GET_TEMPERATURE
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTS,N_DUCTNODES,N_DUCTRUNS,N_TRACKED_SPECIES,HVAC_MASS_TRANSPORT,I_MAX_TEMP,CPBAR_Z,P_INF,NEW
 REAL(EB),INTENT(IN) :: DT
 INTEGER, INTENT(IN) :: NNE
 REAL(EB) :: CPTSUM,DU_DX,ETOT,MFLOW,MSUM,MTOT,TGUESS,VFLOW,ZZ_GET(1:N_TRACKED_SPECIES),&
@@ -1902,7 +1919,7 @@ END SUBROUTINE HVAC_UPDATE
 !> \param NETWORK_INDEX Index indicating which HVAC network is being solved
 
 SUBROUTINE RHSNODE(NETWORK_INDEX)
-USE GLOBAL_CONSTANTS
+USE GLOBAL_CONSTANTS, ONLY: DUCTNODE_NE
 INTEGER, INTENT(IN)::NETWORK_INDEX
 INTEGER :: NN,ND, ARRAYLOC
 TYPE(NETWORK_TYPE), POINTER::NE
@@ -1929,7 +1946,8 @@ END SUBROUTINE RHSNODE
 !> \param NETWORK_INDEX Index indicating which HVAC network is being solved
 
 SUBROUTINE LHSNODE(NETWORK_INDEX)
-USE GLOBAL_CONSTANTS
+
+USE GLOBAL_CONSTANTS, ONLY: DUCTNODE_NE,DUCT_NE
 INTEGER, INTENT(IN)::NETWORK_INDEX
 INTEGER :: NN,ND, ARRAYLOC1,ARRAYLOC2
 TYPE(NETWORK_TYPE), POINTER::NE
@@ -1955,7 +1973,7 @@ END SUBROUTINE LHSNODE
 
 SUBROUTINE DPSTARCALC
 
-USE GLOBAL_CONSTANTS
+USE GLOBAL_CONSTANTS, ONLY: N_ZONE,PSUM,CONNECTED_ZONES,OLD,NEW
 INTEGER :: NN,IPZ,IOPZ
 TYPE(DUCT_TYPE), POINTER::DU
 TYPE(DUCTNODE_TYPE), POINTER::DN
@@ -2001,7 +2019,7 @@ END SUBROUTINE DPSTARCALC
 
 SUBROUTINE RHSDUCT(NETWORK_INDEX)
 
-USE GLOBAL_CONSTANTS
+USE GLOBAL_CONSTANTS, ONLY: DUCT_NE,HVAC_LOCAL_PRESSURE,OLD,GAMMA,N_ZONE,STRATIFICATION,GVEC,PREVIOUS,GUESS
 INTEGER, INTENT(IN)::NETWORK_INDEX
 INTEGER :: ND, ARRAYLOC,IPZ
 REAL(EB) :: HEAD !< DUCT pressure head (Pa)
@@ -2066,13 +2084,14 @@ END SUBROUTINE RHSDUCT
 !> \param NETWORK_INDEX Index indicating which HVAC network is being solved
 
 SUBROUTINE LHSDUCT(NETWORK_INDEX)
-USE GLOBAL_CONSTANTS
-INTEGER, INTENT(IN)::NETWORK_INDEX
+
+USE GLOBAL_CONSTANTS, ONLY: DUCT_NE,PREVIOUS,GUESS,DUCTNODE_NE,HVAC_LOCAL_PRESSURE,GAMMA
+INTEGER, INTENT(IN) :: NETWORK_INDEX
 INTEGER :: NN,ND, ARRAYLOC1,ARRAYLOC2
-TYPE(NETWORK_TYPE), POINTER::NE
-TYPE(DUCT_TYPE), POINTER::DU,DU2
-TYPE(DUCTNODE_TYPE), POINTER::DN,DN2
-TYPE(P_ZONE_TYPE), POINTER::PZ
+TYPE(NETWORK_TYPE), POINTER :: NE
+TYPE(DUCT_TYPE), POINTER :: DU,DU2
+TYPE(DUCTNODE_TYPE), POINTER :: DN,DN2
+TYPE(P_ZONE_TYPE), POINTER :: PZ
 
 NE => NETWORK(NETWORK_INDEX)
 
@@ -2159,7 +2178,9 @@ END SUBROUTINE LHSDUCT
 !> \param ND Index indicating duct where fan is located
 
 SUBROUTINE UPDATE_FAN(T,ND)
-USE MATH_FUNCTIONS, ONLY : EVALUATE_RAMP
+
+USE MATH_FUNCTIONS, ONLY: EVALUATE_RAMP
+USE GLOBAL_CONSTANTS, ONLY: PREVIOUS,OLD,NEW
 INTEGER :: FAN_ITER,DR_INDEX,DR_NF,DR_DU
 INTEGER, INTENT(IN) :: ND
 REAL(EB), INTENT(IN) :: T
@@ -2274,6 +2295,7 @@ SUBROUTINE HVAC_BC_IN(NM)
 
 USE PHYSICAL_FUNCTIONS, ONLY: GET_ENTHALPY
 USE COMPLEX_GEOMETRY, ONLY: CC_FGSC, CC_SOLID
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,PREDICTOR,NULL_BOUNDARY,T_USED
 INTEGER, INTENT(IN) :: NM
 INTEGER :: II,JJ,KK,IW,IOR,IZ1,IZ2,ICF
 INTEGER, POINTER :: NODE_INDEX,VENT_INDEX
@@ -2344,6 +2366,8 @@ SUBROUTINE HVAC_BC_IN(NM)
 
 SUBROUTINE INITIALIZE_HVAC
 
+USE GLOBAL_CONSTANTS, ONLY: CC_IBM,HVAC_LOCAL_PRESSURE,P_INF,N_DUCTS
+
 IF (CELL(CELL_INDEX(BC%IIG,BC%JJG,BC%KKG))%SOLID) RETURN
 IF (CC_IBM .AND. WALL_FLAG .AND. VENT_INDEX > 0) THEN
    IF (FCVAR(BC%IIG,BC%JJG,BC%KKG,CC_FGSC,ABS(VENTS(VENT_INDEX)%IOR)) == CC_SOLID) RETURN
@@ -2351,7 +2375,6 @@ SUBROUTINE INITIALIZE_HVAC
 
 ZONE_LEAK_IF: IF (ALL(SF%LEAK_PATH < 0)) THEN
 
-
    IF (WALL_FLAG) THEN
       IF (VENT_INDEX == 0) RETURN
       IF (VENTS(VENT_INDEX)%NODE_INDEX < 0) RETURN
@@ -2510,12 +2533,14 @@ END SUBROUTINE INITIALIZE_HVAC
 
 END SUBROUTINE HVAC_BC_IN
 
+
 !> \brief Determines what ducts are "fixed"; i.e. they have been given fixed volume or mass flow (including fixed volume fan)
-!>
 !> \param T Current time (s)
 
 SUBROUTINE DETERMINE_FIXED_ELEMENTS(T,CHANGE)
+
 USE MATH_FUNCTIONS,ONLY:EVALUATE_RAMP
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTS,NEW,N_DUCTNODES
 INTEGER:: NN,ND, COUNTER
 REAL(EB), INTENT(IN):: T
 LOGICAL, INTENT(INOUT) :: CHANGE
@@ -2634,6 +2659,8 @@ END SUBROUTINE DETERMINE_FIXED_ELEMENTS
 !> \param T Current time (s)
 
 SUBROUTINE FIND_NETWORKS(CHANGE,T)
+
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTS,N_DUCTNODES,N_ZONE,CONNECTED_ZONES,N_NETWORKS,DUCT_NE,DUCTNODE_NE
 INTEGER:: NZ,NN,ND,DUCT_COUNTER(N_DUCTS),NODE_COUNTER(N_DUCTNODES),COUNTER,COUNTER2,ZONE_COUNTER(N_ZONE),&
           CONNECTED_ZONES2(0:N_ZONE,0:N_ZONE),NETWORK_DCOUNTER(N_DUCTS),NETWORK_NCOUNTER(N_DUCTS),RENUMBER(N_DUCTNODES+N_ZONE)
 LOGICAL, INTENT(OUT) :: CHANGE
@@ -2770,6 +2797,8 @@ END SUBROUTINE FIND_NETWORKS
 !> \brief For each HVAC network the routine defines which ducts and nodes belowng to which element of the HVAC matrix
 
 SUBROUTINE SETUP_SOLUTION_POINTERS
+
+USE GLOBAL_CONSTANTS, ONLY: N_NETWORKS
 INTEGER:: NNE,NN,ND,COUNTER
 TYPE(DUCT_TYPE), POINTER :: DU
 TYPE(DUCTNODE_TYPE), POINTER :: DN
@@ -2802,8 +2831,10 @@ END SUBROUTINE SETUP_SOLUTION_POINTERS
 !> \param NNE Index indicating which HVAC network is being solved
 
 SUBROUTINE UPDATE_LOSS(T,DT,NNE)
-USE PHYSICAL_FUNCTIONS,ONLY:GET_VISCOSITY
-USE MATH_FUNCTIONS,ONLY:EVALUATE_RAMP
+
+USE PHYSICAL_FUNCTIONS, ONLY: GET_VISCOSITY
+USE MATH_FUNCTIONS, ONLY: EVALUATE_RAMP
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,PREVIOUS
 REAL(EB) :: FRICTION_FACTOR,LOSS_SUM,ZZ_GET(1:N_TRACKED_SPECIES),VISCOSITY,AREA,VFLOW
 INTEGER, INTENT(IN) :: NNE
 REAL(EB), INTENT(IN) :: T,DT
@@ -2955,6 +2986,8 @@ END FUNCTION COMPUTE_FRICTION_FACTOR
 !> \param NNE Index indicating which HVAC network is being solved
 
 SUBROUTINE SET_GUESS(NNE,T)
+
+USE GLOBAL_CONSTANTS, ONLY: GUESS,PREVIOUS,NEW
 INTEGER, INTENT(IN) :: NNE
 REAL(EB), INTENT(IN):: T
 INTEGER :: ND
@@ -2990,6 +3023,7 @@ END SUBROUTINE SET_GUESS
 
 SUBROUTINE SET_DONOR(NNE)
 
+USE GLOBAL_CONSTANTS, ONLY: PREVIOUS,NEW
 INTEGER :: ND,NN
 INTEGER, INTENT(IN) :: NNE
 REAL(EB) :: RHOLAST,TMPLAST,FVAL,OMFVAL,ITERFRAC
@@ -3049,6 +3083,8 @@ END SUBROUTINE SET_DONOR
 !> \param NNE Index indicating which HVAC network is being solved
 
 SUBROUTINE CONVERGENCE_CHECK(NNE)
+
+USE GLOBAL_CONSTANTS, ONLY: PREVIOUS,NEW
 INTEGER, INTENT(IN) :: NNE
 INTEGER :: NN, ND, COUNT
 LOGICAL :: CONVERGED
@@ -3117,6 +3153,8 @@ SUBROUTINE COLLAPSE_HVAC_BC(T)
 ! Takes the MPI gathered mesh array of HVAC boundary conditions and updates the DUCTNODE boundary condition values.
 USE PHYSICAL_FUNCTIONS, ONLY : GET_SPECIFIC_GAS_CONSTANT,GET_ENTHALPY,GET_TEMPERATURE
 USE MATH_FUNCTIONS, ONLY : EVALUATE_RAMP
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,N_DUCTNODES,CONNECTED_ZONES,STRATIFICATION,TMPA,I_RAMP_TMP0_Z,I_RAMP_P0_Z,&
+                            RSUM0,RHOA,P_INF,T_BEGIN,HVAC_PRES_RELAX,N_DUCTS,T_USED
 REAL(EB), INTENT(IN) :: T
 REAL(EB) :: TNOW !< Current CPU time (s) used in computing length of time spent in HVAC routines.
 INTEGER:: NN,NS,ND
@@ -3235,6 +3273,8 @@ END SUBROUTINE COLLAPSE_HVAC_BC
 !> \brief Sets current iteration values for duct nodes connected to a vent to the bondary condition value
 
 SUBROUTINE SET_INIT_HVAC
+
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTNODES,N_DUCTS,HVAC_MASS_TRANSPORT_CELL_L,N_TRACKED_SPECIES,RHOA,TMPA,N_ZONE,T_USED
 REAL(EB) :: TNOW !< Current CPU time (s) used in computing length of time spent in HVAC routines.
 REAL(EB) :: XYZ1(3), XYZ2(3)
 INTEGER:: ND,NN,NW,NC
@@ -3315,8 +3355,10 @@ END SUBROUTINE SET_INIT_HVAC
 !> \brief Initializes cell densities, temperatures, specific heats and species for discretized ducts
 
 SUBROUTINE SET_INIT_HVAC_MASS_TRANSPORT
+
 USE MATH_FUNCTIONS, ONLY: EVALUATE_RAMP
 USE PHYSICAL_FUNCTIONS, ONLY: GET_ENTHALPY,GET_SPECIFIC_GAS_CONSTANT
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,N_DUCTS
 REAL(EB) :: P1,P2,T1,T2,ZZ1(1:N_TRACKED_SPECIES),ZZ2(1:N_TRACKED_SPECIES),FAC,RSUM
 INTEGER :: ND,NC
 REAL(EB) :: ZZ_GET(1:N_TRACKED_SPECIES),HGAS
@@ -3360,6 +3402,7 @@ END SUBROUTINE SET_INIT_HVAC_MASS_TRANSPORT
 SUBROUTINE LEAKAGE_HVAC
 
 USE PHYSICAL_FUNCTIONS, ONLY: GET_ENTHALPY
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,N_ZONE,N_DUCTS,N_DUCTNODES,RHOA,TMPA,RSUM0,T_USED
 REAL(EB) :: ZZ_GET(1:N_TRACKED_SPECIES),HGAS,TNOW
 INTEGER :: I_DUCT,I_DUCTNODE,NZ1,NZ2
 TYPE (DUCTNODE_TYPE), POINTER:: DN1,DN2
@@ -3443,8 +3486,9 @@ END SUBROUTINE LEAKAGE_HVAC
 !> \param NODE_INDEX Index of a node containing a filter
 
 SUBROUTINE FILTER_UPDATE(DT,NODE_INDEX)
-!Updates filter loss and loading solution
+
 USE MATH_FUNCTIONS,ONLY:EVALUATE_RAMP
+USE GLOBAL_CONSTANTS, ONLY: PREVIOUS,NEW
 INTEGER,INTENT(IN)::NODE_INDEX
 REAL(EB), INTENT(IN) :: DT
 REAL(EB) :: TOTAL_LOADING
@@ -3487,6 +3531,8 @@ END SUBROUTINE FILTER_UPDATE
 !> \param T Current time (s)
 
 SUBROUTINE COIL_UPDATE(T)
+
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTS,NEW
 REAL(EB), INTENT(IN) :: T
 INTEGER :: ND
 TYPE(DUCT_TYPE),POINTER::DU
@@ -3529,8 +3575,10 @@ END SUBROUTINE COIL_UPDATE
 !> \param AREA_D Duct area (m2)
 
 SUBROUTINE CALC_COIL_Q(AC_INDEX,COIL_Q,TSI,VEL_D,TMP_D,ZZ_D,RHO_D,CP_D,AREA_D)
-USE MATH_FUNCTIONS, ONLY : EVALUATE_RAMP
-USE PHYSICAL_FUNCTIONS, ONLY : GET_SPECIFIC_HEAT, GET_AVERAGE_SPECIFIC_HEAT, GET_ENTHALPY
+
+USE MATH_FUNCTIONS, ONLY: EVALUATE_RAMP
+USE PHYSICAL_FUNCTIONS, ONLY: GET_SPECIFIC_HEAT, GET_AVERAGE_SPECIFIC_HEAT, GET_ENTHALPY
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,I_MAX_TEMP
 INTEGER, INTENT(IN) :: AC_INDEX
 REAL(EB), INTENT(IN) :: TSI,VEL_D,TMP_D,ZZ_D(1:N_TRACKED_SPECIES),RHO_D,CP_D,AREA_D
 REAL(EB), INTENT(INOUT) :: COIL_Q
@@ -3586,6 +3634,7 @@ END SUBROUTINE CALC_COIL_Q
 
 SUBROUTINE ADJUST_LEAKAGE_AREA
 
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTS
 INTEGER :: ND
 REAL(EB) :: N,DELTA_P,DELTA_P_REF,C_D
 TYPE(DUCT_TYPE), POINTER :: DU
@@ -3613,7 +3662,9 @@ END SUBROUTINE ADJUST_LEAKAGE_AREA
 !> \param DT Current time step (s)
 
 SUBROUTINE UPDATE_HVAC_MASS_TRANSPORT(DT,NR)
+
 USE PHYSICAL_FUNCTIONS,ONLY: GET_TEMPERATURE, GET_ENTHALPY
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,NEW
 REAL(EB), INTENT(IN) :: DT
 INTEGER, INTENT(IN) :: NR
 INTEGER :: N_SUBSTEPS,ND,NS,NC,MAX_CELLS
@@ -3696,6 +3747,8 @@ END SUBROUTINE UPDATE_HVAC_MASS_TRANSPORT
 !> \brief Checks duct network for minimal loss defintions
 
 SUBROUTINE EXAMINE_LOSSES
+
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTNODES,N_DUCTS
 INTEGER :: ND, ND2, ND3, NN, F_COUNTER
 LOGICAL :: CHANGE
 LOGICAL :: LOSS_D(N_DUCTS,2),LOSS_N(N_DUCTNODES),FIXED_D(N_DUCTS)
@@ -4011,6 +4064,8 @@ END SUBROUTINE EXAMINE_LOSSES
 !> \param T Current simulation time (s)
 
 SUBROUTINE HVAC_QFAN_CALC(T)
+
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTRUNS,GUESS,N_AIRCOILS,PREVIOUS,OLD,NEW
 REAL(EB), INTENT(IN) :: T
 INTEGER :: NR,NF
 TYPE(DUCTRUN_TYPE), POINTER :: DR
@@ -4074,6 +4129,8 @@ END SUBROUTINE HVAC_QFAN_CALC
 !> \param NF Index indicating which ductrun fan is being solved
 
 SUBROUTINE SET_GUESS_QFAN(DUCTRUN_INDEX,NF)
+
+USE GLOBAL_CONSTANTS, ONLY: GUESS,PREVIOUS,NEW
 INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
 INTEGER :: ND
 TYPE(DUCTRUN_TYPE), POINTER :: DR
@@ -4124,7 +4181,9 @@ END SUBROUTINE QFAN_SIMPLE
 !> \brief Finds "duct runs"; being ductnodes and ducts directly (via HVAC components) connected to one another
 
 SUBROUTINE FIND_DUCTRUNS(CHANGE)
-USE PHYSICAL_FUNCTIONS, ONLY : GET_ENTHALPY
+
+USE PHYSICAL_FUNCTIONS, ONLY: GET_ENTHALPY
+USE GLOBAL_CONSTANTS, ONLY: N_DUCTS,N_DUCTNODES,N_TRACKED_SPECIES,N_DUCTRUNS,P_INF,N_DUCTRUNS,HVAC_QFAN,TMPA,RHOA,OLD
 LOGICAL, INTENT(IN) :: CHANGE
 INTEGER :: NN,NR,NF,NN3,ND,DUCT_COUNTER(N_DUCTS),NODE_COUNTER(N_DUCTNODES),&
            DR_DUCTS(N_DUCTS),DR_DUCTNODES(N_DUCTS),DUCTRUN_MAP(N_DUCTS),DR_INDEX
@@ -4379,7 +4438,9 @@ END SUBROUTINE FIND_DUCTRUNS
 !> \param NF Index indicating which HVAC ductrun fan is being solved
 
 SUBROUTINE MATRIX_SOLVE_QFAN(DUCTRUN_INDEX,NF)
+
 USE MATH_FUNCTIONS,ONLY : GAUSSJ
+USE GLOBAL_CONSTANTS, ONLY: NEW
 INTEGER,INTENT(IN) :: DUCTRUN_INDEX,NF
 INTEGER :: IERR
 REAL(EB), ALLOCATABLE, DIMENSION(:,:) :: LHS_GAUSSJ
@@ -4408,12 +4469,12 @@ END SUBROUTINE MATRIX_SOLVE_QFAN
 !> \param DUCTRUN_INDEX Index indicating which HVAC ductrun is being solved
 
 SUBROUTINE RHSNODE_QFAN(DUCTRUN_INDEX)
-USE GLOBAL_CONSTANTS
-INTEGER, INTENT(IN)::DUCTRUN_INDEX
+
+INTEGER, INTENT(IN) :: DUCTRUN_INDEX
 INTEGER :: NN,ND
-TYPE(DUCTRUN_TYPE), POINTER::DR
-TYPE(DUCT_TYPE), POINTER::DU
-TYPE(DUCTNODE_TYPE), POINTER::DN
+TYPE(DUCTRUN_TYPE), POINTER :: DR
+TYPE(DUCT_TYPE), POINTER :: DU
+TYPE(DUCTNODE_TYPE), POINTER :: DN
 
 DR => DUCTRUN(DUCTRUN_INDEX)
 DO NN = 1, DR%N_M_DUCTNODES
@@ -4432,12 +4493,12 @@ END SUBROUTINE RHSNODE_QFAN
 !> \param NF Index indicating which ductrun fan is being solved
 
 SUBROUTINE LHSNODE_QFAN(DUCTRUN_INDEX,NF)
-USE GLOBAL_CONSTANTS
-INTEGER, INTENT(IN)::DUCTRUN_INDEX,NF
+
+INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
 INTEGER :: NN,ND,ARRAYLOC
-TYPE(DUCTRUN_TYPE), POINTER::DR
-TYPE(DUCT_TYPE), POINTER::DU
-TYPE(DUCTNODE_TYPE), POINTER::DN
+TYPE(DUCTRUN_TYPE), POINTER :: DR
+TYPE(DUCT_TYPE), POINTER :: DU
+TYPE(DUCTNODE_TYPE), POINTER :: DN
 
 DR => DUCTRUN(DUCTRUN_INDEX)
 DO NN = 1, DR%N_M_DUCTNODES
@@ -4460,7 +4521,7 @@ END SUBROUTINE LHSNODE_QFAN
 
 SUBROUTINE RHSDUCT_QFAN(DUCTRUN_INDEX,NF,T)
 
-USE GLOBAL_CONSTANTS
+USE GLOBAL_CONSTANTS, ONLY: HVAC_LOCAL_PRESSURE,OLD,GAMMA,STRATIFICATION,GVEC,PREVIOUS,GUESS
 INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
 REAL(EB), INTENT(IN) :: T
 INTEGER :: ND
@@ -4518,12 +4579,13 @@ END SUBROUTINE RHSDUCT_QFAN
 !> \param NF Index indicating which ductrun fan is being solved
 
 SUBROUTINE LHSDUCT_QFAN(DUCTRUN_INDEX,NF)
-USE GLOBAL_CONSTANTS
-INTEGER, INTENT(IN)::DUCTRUN_INDEX,NF
+
+USE GLOBAL_CONSTANTS, ONLY: PREVIOUS,GUESS,HVAC_LOCAL_PRESSURE,GAMMA
+INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
 INTEGER :: ND
-TYPE(DUCTRUN_TYPE), POINTER::DR
-TYPE(DUCT_TYPE), POINTER::DU
-TYPE(DUCTNODE_TYPE), POINTER::DN
+TYPE(DUCTRUN_TYPE), POINTER :: DR
+TYPE(DUCT_TYPE), POINTER :: DU
+TYPE(DUCTNODE_TYPE), POINTER :: DN
 
 DR => DUCTRUN(DUCTRUN_INDEX)
 
@@ -4569,6 +4631,8 @@ END FUNCTION FAN_MAX
 !> \param NF Index indicating which HVAC ductrun fan is being solved
 
 SUBROUTINE CONVERGENCE_CHECK_QFAN(DUCTRUN_INDEX,NF)
+
+USE GLOBAL_CONSTANTS, ONLY: PREVIOUS,NEW
 INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
 INTEGER :: NN, ND, COUNT
 REAL(EB) :: MSUM,MTOT,MFLOW,VEL
@@ -4622,8 +4686,10 @@ END SUBROUTINE CONVERGENCE_CHECK_QFAN
 !> \param T Current time (s)
 
 SUBROUTINE COIL_UPDATE_QFAN(T,DUCTRUN_INDEX,NF)
+
 USE MATH_FUNCTIONS, ONLY : EVALUATE_RAMP
 USE PHYSICAL_FUNCTIONS, ONLY : GET_SPECIFIC_HEAT, GET_AVERAGE_SPECIFIC_HEAT, GET_ENTHALPY
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,OLD,NEW
 INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
 REAL(EB), INTENT(IN) :: T
 REAL(EB) :: COIL_ON_TIME,DVEL
@@ -4668,8 +4734,10 @@ END SUBROUTINE COIL_UPDATE_QFAN
 !> \param NF Index indicating which HVAC ductrun dan is being solved
 
 SUBROUTINE UPDATE_LOSS_QFAN(T,DUCTRUN_INDEX,NF)
-USE PHYSICAL_FUNCTIONS,ONLY:GET_VISCOSITY
-USE MATH_FUNCTIONS,ONLY:EVALUATE_RAMP
+
+USE PHYSICAL_FUNCTIONS, ONLY: GET_VISCOSITY
+USE MATH_FUNCTIONS, ONLY: EVALUATE_RAMP
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,PREVIOUS,OLD,NEW
 REAL(EB) :: FRICTION_FACTOR,LOSS_SUM,ZZ_GET(1:N_TRACKED_SPECIES),VISCOSITY,VFLOW,AREA,DVEL
 INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
 REAL(EB), INTENT(IN) :: T
@@ -4845,6 +4913,7 @@ END SUBROUTINE UPDATE_LOSS_QFAN
 
 SUBROUTINE SET_DONOR_QFAN(DUCTRUN_INDEX,NF)
 
+USE GLOBAL_CONSTANTS, ONLY: NEW
 INTEGER :: ND,NN
 INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
 REAL(EB) :: DVEL
@@ -4922,7 +4991,8 @@ END SUBROUTINE SET_DONOR_QFAN
 
 SUBROUTINE HVAC_UPDATE_QFAN(DUCTRUN_INDEX,NF)
 
-USE PHYSICAL_FUNCTIONS, ONLY : GET_TEMPERATURE,GET_SPECIFIC_GAS_CONSTANT,GET_ENTHALPY
+USE PHYSICAL_FUNCTIONS, ONLY: GET_TEMPERATURE,GET_SPECIFIC_GAS_CONSTANT,GET_ENTHALPY
+USE GLOBAL_CONSTANTS, ONLY: N_TRACKED_SPECIES,N_DUCTS,N_DUCTNODES,STRATIFICATION,GVEC,P_INF,NEW
 REAL(EB) :: CPTSUM,ETOT,MTOT,TGUESS,VFLOW,ZZ_GET(1:N_TRACKED_SPECIES),&
             ZZTOT(1:N_TRACKED_SPECIES),HGAS,RSUM,DVEL
 INTEGER, INTENT(IN) :: DUCTRUN_INDEX,NF
diff --git a/Source/main.f90 b/Source/main.f90
index b848925a628..9858e69691e 100644
--- a/Source/main.f90
+++ b/Source/main.f90
@@ -21,7 +21,9 @@ PROGRAM FDS
 USE RADCONS, ONLY : DLN
 USE MISC_FUNCTIONS, ONLY : WRITE_SUMMARY_INFO,VERBOSE_PRINTOUT
 USE OUTPUT_DATA
-USE MEMORY_FUNCTIONS
+USE MEMORY_FUNCTIONS, ONLY: EXCHANGE_GEOMETRY_INFO,CHKMEMERR,ALLOCATE_STORAGE,PACK_PARTICLE,&
+                            NULLIFY_PARTICLE,PACK_WALL,REALLOCATE_P_ZONE,REALLOCATE_CELL,REALLOCATE_STORAGE_ARRAYS,&
+                            RE_ALLOCATE_STRINGS,PACK_THIN_WALL
 USE HVAC_ROUTINES
 USE COMP_FUNCTIONS, ONLY : CURRENT_TIME,INITIALIZE_OUTPUT_CLOCKS,READ_EXTERNAL_FILE,GET_FILE_NUMBER
 USE DEVICE_VARIABLES
diff --git a/Source/turb.f90 b/Source/turb.f90
index a9450fe7731..c91046d3bab 100644
--- a/Source/turb.f90
+++ b/Source/turb.f90
@@ -7,7 +7,7 @@ MODULE TURBULENCE
 USE GLOBAL_CONSTANTS
 USE MESH_POINTERS
 USE MESH_VARIABLES
-USE COMP_FUNCTIONS
+USE COMP_FUNCTIONS, ONLY: GET_FILE_NUMBER,SHUTDOWN
 
 IMPLICIT NONE (TYPE,EXTERNAL)
 PRIVATE

From 8c06cf323ea9446facf110bf612e2a1a4784ba3e Mon Sep 17 00:00:00 2001
From: mcgratta <mcgratta@gmail.com>
Date: Tue, 10 Mar 2026 16:18:13 -0400
Subject: [PATCH 4/6] FDS Source: Remove unused variables

---
 Source/hvac.f90 | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Source/hvac.f90 b/Source/hvac.f90
index 62fbc016af3..8b5ab2819fd 100644
--- a/Source/hvac.f90
+++ b/Source/hvac.f90
@@ -2366,7 +2366,7 @@ SUBROUTINE HVAC_BC_IN(NM)
 
 SUBROUTINE INITIALIZE_HVAC
 
-USE GLOBAL_CONSTANTS, ONLY: CC_IBM,HVAC_LOCAL_PRESSURE,P_INF,N_DUCTS
+USE GLOBAL_CONSTANTS, ONLY: CC_IBM,HVAC_LOCAL_PRESSURE,P_INF
 
 IF (CELL(CELL_INDEX(BC%IIG,BC%JJG,BC%KKG))%SOLID) RETURN
 IF (CC_IBM .AND. WALL_FLAG .AND. VENT_INDEX > 0) THEN
@@ -2768,6 +2768,7 @@ SUBROUTINE FIND_NETWORKS(CHANGE,T)
 NETWORK_NCOUNTER=0
 COUNTER = 0
 DO ND = 1, N_DUCTS
+write(0,*) ND,N_DUCTS,UBOUND(NETWORK),DUCT_COUNTER(ND)
    NETWORK(DUCT_COUNTER(ND))%N_DUCTS = NETWORK(DUCT_COUNTER(ND))%N_DUCTS + 1
 ENDDO
 DO NN = 1, N_DUCTNODES
@@ -3023,7 +3024,7 @@ END SUBROUTINE SET_GUESS
 
 SUBROUTINE SET_DONOR(NNE)
 
-USE GLOBAL_CONSTANTS, ONLY: PREVIOUS,NEW
+USE GLOBAL_CONSTANTS, ONLY: PREVIOUS
 INTEGER :: ND,NN
 INTEGER, INTENT(IN) :: NNE
 REAL(EB) :: RHOLAST,TMPLAST,FVAL,OMFVAL,ITERFRAC
@@ -3488,7 +3489,7 @@ END SUBROUTINE LEAKAGE_HVAC
 SUBROUTINE FILTER_UPDATE(DT,NODE_INDEX)
 
 USE MATH_FUNCTIONS,ONLY:EVALUATE_RAMP
-USE GLOBAL_CONSTANTS, ONLY: PREVIOUS,NEW
+USE GLOBAL_CONSTANTS, ONLY: PREVIOUS
 INTEGER,INTENT(IN)::NODE_INDEX
 REAL(EB), INTENT(IN) :: DT
 REAL(EB) :: TOTAL_LOADING

From a6396c50be679605699f150da35b96ea085ca596 Mon Sep 17 00:00:00 2001
From: mcgratta <mcgratta@gmail.com>
Date: Tue, 10 Mar 2026 16:20:02 -0400
Subject: [PATCH 5/6] FDS Source: Remove write statement

---
 Source/hvac.f90 | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Source/hvac.f90 b/Source/hvac.f90
index 8b5ab2819fd..0c3bcf332b8 100644
--- a/Source/hvac.f90
+++ b/Source/hvac.f90
@@ -2768,7 +2768,6 @@ SUBROUTINE FIND_NETWORKS(CHANGE,T)
 NETWORK_NCOUNTER=0
 COUNTER = 0
 DO ND = 1, N_DUCTS
-write(0,*) ND,N_DUCTS,UBOUND(NETWORK),DUCT_COUNTER(ND)
    NETWORK(DUCT_COUNTER(ND))%N_DUCTS = NETWORK(DUCT_COUNTER(ND))%N_DUCTS + 1
 ENDDO
 DO NN = 1, N_DUCTNODES

From 48b8a4731e594d255d535e7d57cf080620d652c7 Mon Sep 17 00:00:00 2001
From: ericvmueller <ericvmueller@gmail.com>
Date: Tue, 10 Mar 2026 17:38:31 -0400
Subject: [PATCH 6/6] FDS Technical Reference Guide: clarify use of back-side
 natural convection correlation

---
 Manuals/FDS_Technical_Reference_Guide/Solid_Chapter.tex | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Manuals/FDS_Technical_Reference_Guide/Solid_Chapter.tex b/Manuals/FDS_Technical_Reference_Guide/Solid_Chapter.tex
index 36e361033f7..74a5aca2a49 100644
--- a/Manuals/FDS_Technical_Reference_Guide/Solid_Chapter.tex
+++ b/Manuals/FDS_Technical_Reference_Guide/Solid_Chapter.tex
@@ -121,7 +121,7 @@ \subsubsection{Empirical Natural/Forced Convection Model}
                                                 2 +  0.454 \, \hbox{Ra}^{1/4}                         &  \hbox{Sphere}
        \end{array} \right.
 \ee
-\footnotetext{The heat transfer coefficient for a vertical plate or cylinder is simplified to $h=1.31 \, (\Delta T)^{1/3}$~\cite{Holman:2} in cases where the back side of a solid obstruction is outside the computational domain and the gas temperature is assumed to be ambient. }
+\footnotetext{The heat transfer coefficient for a vertical plate or cylinder is simplified to $h=1.31 \, (\Delta T)^{1/3}$~\cite{Holman:2} when the back side of a solid obstruction is outside the computational domain or \ct{BACKING='VOID'}, and the back side gas temperature is assumed to be ambient or is user-specified. }
 For forced convection, the Nusselt number takes the form:
 \be
    \NU_{\rm forced} = C_0 + \left( C_1 \, \RE^n - C_2 \right) \, \PR^m  \quad ; \quad \RE = \frac{\rho |\bu| L}{\mu}  \quad ; \quad m=1/3