Since the vapor must move across the alveolar-capillary membrane, a limitation due to diffusion may occur. This is not so for solvents being investigated. There is sufficient time for an equilibrium to occur between the two compartments. Therefore an equilibrium is assumed to exist at all times between alveolar air and capillary blood.

iv) Amount of Blood and Body Water to be Saturated

5 liters and total body water, 40 liters.

v) Amount of Fatty Tissue to be Saturated » 15% of bw

vi) Biotransformation or Metabolism

To the extent that a chemical is metabolized, this will reduce its amount in blood and therefore uptake will continue. Usually this is via an enzymatic saturable pathway and will be important at low concentration. At high concentration the amount of chemicals metabolized will be too low to influence the equilibrium concentration in blood.