diff --git a/particula/aerosol_dynamics/parcel.py b/particula/aerosol_dynamics/parcel.py
index edd1f2b..1cbab4f 100644
--- a/particula/aerosol_dynamics/parcel.py
+++ b/particula/aerosol_dynamics/parcel.py
@@ -1,21 +1,20 @@
-"""class for creating a air parcel to put particles and gases in.
+"""class for creating an air parcel to put particles and gases into.
 """
 
 import numpy as np
-from particula import u
 from particula.aerosol_dynamics import particle
 
 
 class Parcel:
     """
-    Creates an air parcel to track and interact with a list of particle objects.
-    This starts the base for particle and gas dynamic simulations.
-    For example, eveolution of a size distribution with time.
+    Creates an air parcel to track and interact with a list of particle
+    objects. This is the basis for particle and gas dynamic simulations.
+    For example, evolution of a size distribution with time.
 
     Attributes:
         name            (str)               The name of the parcel.
         particle_data   (particle list)     Particle objects.
-        enviroment      (object)            Parcel's enviroment.
+        environment     (object)            Parcel's environment.
     """
 
     def __init__(self, name: str, parcel_environment):
@@ -25,11 +24,12 @@ class Parcel:
         Parameters:
             name           (str),
             particle_data  (object numpy array),
-            enviroment     (object).
+            environment     (object).
         """
         self._name = name
         self._particle_data = np.array([])
         self._enviroment = parcel_environment
+        self.unit_warning_flag = True
 
     def name(self) -> str:
         """Returns the name of the parcel."""
@@ -45,8 +45,8 @@ class Parcel:
     def create_and_add_particle(
         self, name: str,
         radius,
-        density=1e3 * u.kg / u.m**3,
-        charge=0 * u.dimensionless
+        density=1e3,
+        charge=0
     ):
         """Create and then add a particle to the parcel.
 
@@ -57,11 +57,14 @@ class Parcel:
             density (float) [kg/m**3]       default = 1e3 [kg/m**3],
             charge  (int)   [dimensionless] default = 0 [dimensionless]
         """
-
         try:  # maybe move to particle class
             radius.check('m')
         except AttributeError:
-            print('Please add units to radius. E.g., radius = 150 * u.nm]')
+            if self.unit_warning_flag:
+                print(
+                    "Warning: radius has no units, assuming [m]."
+                )
+                self.unit_warning_flag = False
 
         self.add_particle(
             particle.Particle(name, radius, density, charge)
@@ -70,35 +73,35 @@ class Parcel:
     def create_and_add_list_of_particle(
         self,
         name_of_particles,
-        radi_of_particles,
+        radii_of_particles,
         densities_of_particles=None,
         charges_of_particles=None
     ):
         """Adds a list of particles to the parcel based on size only (simple).
-            or delcaring denisties and charges (detailed).
+            or with densities and charges (detailed).
         Parameters:
             name_of_particles   (str)   [no units],
-            radi_of_particles (list)  [m]
+            radii_of_particles (list)  [m]
         Optional:
             densities_of_particles (list) [kg/m**3],
             charges_of_particles  (list) [dimensionless]
         Examples:
             simple: parcel.create_and_add_list_of_particle(
                 'org2',
-                [1e-9, 2e-9, 3e-9] * u.m
+                [1e-9, 2e-9, 3e-9]
                 )
             detailed: create_and_add_list_of_particle(
                 'org3',
-                [1e-9, 2e-9, 3e-9] * u.m,
-                [1.8, 1, 1] * u.kg / u.m ** 3,
-                [1, 0, 2] * u.dimensionless)
+                [1e-9, 2e-9, 3e-9],
+                [1.8e3, 1e3, 1e3],
+                [1, 0, 2])
         """
         if densities_of_particles is None:
-            for size_add in radi_of_particles:
+            for size_add in radii_of_particles:
                 self.create_and_add_particle(name_of_particles, size_add)
         else:
             for size_add, density_add, charge_add in zip(
-                radi_of_particles,
+                radii_of_particles,
                 densities_of_particles,
                 charges_of_particles
             ):
@@ -125,8 +128,8 @@ class Parcel:
         """Returns the mass of the particle. Checks units. [kg]"""
         return [i.mass() for i in self.particle_classes_list()]
 
-    def particle_radi_list(self) -> float:
-        """Returns list of radi of particles"""
+    def particle_radii_list(self) -> float:
+        """Returns list of radii of particles"""
         return [i.radius() for i in self.particle_classes_list()]
 
     def particle_densities_list(self) -> float:
@@ -140,5 +143,59 @@ class Parcel:
     def particle_knudsen_numbers_list(self) -> float:
         """Returns list of knudsen numbers of particles."""
         return [
-            i.knudsen_number(self._enviroment) for i in self.particle_classes_list()
+            i.knudsen_number(self._enviroment)
+            for i in self.particle_classes_list()
+        ]
+
+    def particle_dimensioned_coagulation_kernel_list(
+        self,
+        other,
+        authors: str = "cg2019",
+    ) -> float:
+        """Returns list of dimensioned coagulation kernel of given particle
+        (other) to the list of particles in the parcel. [m**3/s]
+        Parameters:
+
+            self:           particle_classes_list
+            other:          particle 2
+            authors:        authors of the parameterization
+                - gh2012    https://doi.org/10.1103/PhysRevE.78.046402
+                - cg2020    https://doi.org/XXXXXXXXXXXXXXXXXXXXXXXXXX
+                - hard_sphere
+                (default: cg2019)
+        """
+        return [
+            i.dimensioned_coagulation_kernel(other, self._enviroment, authors)
+            for i in self.particle_classes_list()
         ]
+
+    def particle_dimensionless_coagulation_kernel_list(
+        self,
+        other,
+        authors: str = "cg2019",
+    ) -> float:
+        """Returns list of dimensioned coagulation kernel of given particle
+        (other) to the list of particles in the parcel. [m**3/s]
+        Parameters:
+
+            self:           particle_classes_list
+            other:          particle 2
+            authors:        authors of the parameterization
+                - gh2012    https://doi.org/10.1103/PhysRevE.78.046402
+                - cg2020    https://doi.org/XXXXXXXXXXXXXXXXXXXXXXXXXX
+                - hard_sphere
+                (default: cg2019)
+        """
+        return [
+            i.dimensionless_coagulation_kernel_parameterized(
+                other, self._enviroment, authors
+            )
+            for i in self.particle_classes_list()
+        ]
+
+
+def get_magnitude_only(list_of_properties) -> float:
+    """strips units from the numpy array and returns the magnitude."""
+    return [
+        i.magnitude for i in list_of_properties
+    ]

diff --git a/particula/aerosol_dynamics/tests/parcel_test.py b/particula/aerosol_dynamics/tests/parcel_test.py
index eedb634..26f6cbd 100644
--- a/particula/aerosol_dynamics/tests/parcel_test.py
+++ b/particula/aerosol_dynamics/tests/parcel_test.py
@@ -19,8 +19,8 @@ large_particle = particle.Particle(
 )
 
 standard_environment = environment.Environment(
-    temperature=298 * u.K,
-    pressure=101325 * u.Pa,
+    temperature=298,
+    pressure=101325,
 )
 
 # create a parcel
@@ -29,12 +29,12 @@ simple_parcel = parcel.Parcel('simple', standard_environment)
 # add single particle to parcel
 simple_parcel.add_particle(small_particle)
 simple_parcel.add_particle(large_particle)
-simple_parcel.create_and_add_particle('org1', 500*u.nm)
+simple_parcel.create_and_add_particle('org1', 500)
 # add multiple particles to parcel
-simple_parcel.create_and_add_list_of_particle('org2', [1e-9, 2e-9, 3e-9] * u.m)
+simple_parcel.create_and_add_list_of_particle('org2', [1e-9, 2e-9, 3e-9])
 simple_parcel.create_and_add_list_of_particle(
-    'org2', [1e-9, 2e-9, 3e-9] * u.m,
-    [1.8, 1, 1] * u.kg / u.m ** 3, [1, 0, 2] * u.dimensionless
+    'org2', [1e-9, 2e-9, 3e-9],
+    [1.8, 1, 1], [1, 0, 2]
 )
 
 
@@ -44,8 +44,18 @@ def test_getters():
     """
     assert len(simple_parcel.particle_classes_list()) == 9
     assert len(simple_parcel.particle_masses_list()) == 9
-    assert len(simple_parcel.particle_radi_list()) == 9
+    assert len(simple_parcel.particle_radii_list()) == 9
     assert len(simple_parcel.particle_charges_list()) == 9
+    assert len(
+        simple_parcel.particle_dimensioned_coagulation_kernel_list(
+            large_particle
+        )
+    ) == 9
+    assert len(
+        simple_parcel.particle_dimensionless_coagulation_kernel_list(
+            large_particle
+        )
+    ) == 9
 
 
 def test_particle_mass_units():
@@ -62,7 +72,9 @@ def test_particle_radius_units():
     '''
     Test that the radius of the particles is returned in m
     '''
-    assert sum([i.check('m') for i in simple_parcel.particle_radi_list()]) == 9
+    assert sum(
+        [i.check('m') for i in simple_parcel.particle_radii_list()]
+    ) == 9
 
 
 def test_particle_density_units():
@@ -95,6 +107,33 @@ def test_particle_knudsen_number():
     ) == 9
 
 
+def test_particle_dimensioned_coagulation_kernel_list():
+    '''
+    Test that the dimensioned coagulation kernel list is returned in m^3/s
+    '''
+    assert sum(
+        [i.check(u.m ** 3 / u.s)
+            for i in
+            simple_parcel.particle_dimensioned_coagulation_kernel_list(
+                large_particle
+            )]
+    ) == 9
+
+
+def test_particle_dimensionless_coagulation_kernel_list():
+    '''
+    Test that the dimensionless coagulation kernel list is returned
+    in dimensionless
+    '''
+    assert sum(
+        [i.check(u.dimensionless)
+            for i in
+            simple_parcel.particle_dimensionless_coagulation_kernel_list(
+                large_particle
+            )]
+    ) == 9
+
+
 def test_remove_particle():
     '''
     Test that the remove particle method works

add particle to particle interacations in parcel class
https://github.com/uncscode/particula/blob/85ba3f80b2f6d5b7d87c0e9f1a848d1bb9d86e94/aerosol_dynamics/parcel.py#L98
particula/aerosol_dynamics/tests/parcel_test.py::test_getters particula/aerosol_dynamics/tests/parcel_test.py::test_particle_mass_units particula/aerosol_dynamics/tests/parcel_test.py::test_particle_radius_units particula/aerosol_dynamics/tests/parcel_test.py::test_particle_dimensioned_coagulation_kernel_list particula/aerosol_dynamics/tests/parcel_test.py::test_particle_dimensionless_coagulation_kernel_list
particula/aerosol_dynamics/tests/parcel_test.py::test_particle_density_units particula/aerosol_dynamics/tests/parcel_test.py::test_particle_charge_units particula/aerosol_dynamics/tests/parcel_test.py::test_particle_knudsen_number particula/aerosol_dynamics/tests/parcel_test.py::test_remove_particle particula/aerosol_dynamics/tests/parcel_test.py::test_remove_all_particles