diff --git a/src/pykoala/data_container.py b/src/pykoala/data_container.py
index b494d5bd..85a87c5f 100644
--- a/src/pykoala/data_container.py
+++ b/src/pykoala/data_container.py
@@ -2,8 +2,10 @@
 This module contains the parent class that represents the data used during the
 reduction process
 """
+import numpy as np
 
 from astropy.io.fits import Header
+from astropy.nddata import bitmask
 
 from pykoala.exceptions.exceptions import NoneAttrError
 
@@ -248,7 +250,132 @@ class Parameter(object):
     """Class that represents some parameter and associated metadata"""
     def __init__(self) -> None:
         pass
+
+class GenericFlagMap(bitmask.BitFlagNameMap):
+    """PyKOALA generic BitMask flag map.
+    
+    Attributes
+    ----------
+    - CR: Cosmic ray (2)
+    - HP: Hot pixel (4)
+    - DP: Dark pixel (8)
+
+    Example
+    -------
+    Accessing the description of each BitFlag is possible by
+    `GenericFlagMap.FLAG_NAME.__doc__`
+    """
+    CR = 2, 'Cosmic ray'
+    HP = 4, 'Hot pixel'
+    DP = 8, 'Dark pixel'
     
+class DataMask(object):
+    """This class contains mask information of DataContainers.
+    
+    Description
+    -----------
+    This class represents a bitmask of a data structure defined by a given
+    dimensionality shape.
+
+    Attributes
+    ----------
+    - data: (np.ndarray)
+        The mask data values.
+    - flag_map: (astropy.bitmask.BitFlagNameMap)
+        A mapping between the flag names and their numerical values.
+
+    Methods
+    -------
+    - get_flags
+    - add_flags
+    - get_mask
+    """
+    def __init__(self, shape, flag_map=GenericFlagMap):
+        # Initialise the mask with all pixels being valid
+        self.data = np.zeros(shape, dtype=int)
+        self.flag_map = flag_map
+
+    def get_flags(self):
+        """Return the current flags used in the mask."""
+        att = list(self.flag_map.__dict__)
+        return [a for a in att if "_" not in a]
+
+    def get_flag_values(self):
+        """Get the values associated to the flags"""
+        flags = self.get_flags()
+        values = {}
+        for flag in flags:
+            values[flag] = getattr(self.flag_map, flag).real
+        return values
+
+    def get_description(self):
+        """Get the description of the BitFlags."""
+        flags = self.get_flags()
+        doc = {}
+        for flag in flags:
+            doc[flag] = getattr(self.flag_map, flag).__doc__
+        return doc
+
+    def add_flags(self, **extra_flags):
+        """Add a new flag to the mask."""
+        self.flag_map = bitmask.extend_bit_flag_map(
+            "DQ_MASK", self.flag_map, **extra_flags)
+
+    def get_mask(self, use_flags=None, use_bits=None, ignore_flags=None,
+                 ignore_bits=None, dtype=bool):
+        """Get a mask.
+        
+        Description
+        -----------
+        This method returns a mask computed by including or excluding a list
+        of bitmask values.
+
+        Parameters
+        ----------
+        - use_flags: (list, default=None)
+            A list of strings corresponding to the flag names to be included.
+        - use_bits: (list, default=None)
+            A list of bitmask values to be included in the mask. This is ignored
+            if `use_flags` is provided.
+        - ignore_flags: (list, default=None)
+            A list of strings corresponding to the flags to be excluded. Only
+            used if `use_flags` and `use_bits` are `None`.
+        - ignore_bits: (list, default=None)
+            A list of bitmask values to be excluded in the mask. This is ignored
+            if any of the other arguments is not `None`.
+        - dtype: (type, default=bool)
+            Data type of the output mask
+        Example
+        -------
+        ```
+        # Create a mask
+        mask = DataMask()
+        # Get a mask for all flagged pixels
+        total_mask = mask.get_mask()
+        # Get a mask only for pixels flagged as cosmic rays (CR)
+        cr_mask = mask.get_mask(use_flags=['CR'])
+        ```
+        """
+        flags = self.get_flag_values()
+        flag_names = list(flags.keys())
+        flag_values = list(flags.values())
+        if use_flags is not None:
+            flags_to_ignore = [f for f in flag_names if f not in use_flags]
+        elif use_bits is not None:
+            flags_to_ignore = [f for f in flag_names if flag_values[
+                flag_names.index(f)] not in use_bits]
+        elif ignore_flags is not None:
+            flags_to_ignore = ignore_flags
+        elif ignore_bits is not None:
+            flags_to_ignore = [f for f in flag_names if flag_values[
+                flag_names.index(f)] in ignore_bits]
+        else:
+            flags_to_ignore = []
+        print(flags_to_ignore)
+        return bitmask.bitfield_to_boolean_mask(self.data,
+                                                ignore_flags=flags_to_ignore,
+                                                flag_name_map=self.flag_map,
+                                                dtype=dtype)
 
 class DataContainer(object):
     """