External contamination results when radioactive material is deposited on skin, hair, eyes, or other external structures, much like mud or dust.
External contamination stops when the material is removed by shedding contaminated clothes and/or completely washing off the contamination.
Types of external contamination
Full body: entire person is covered with radioactive material, not necessarily homogeneously
Partial body: shielding blocks radioactive material from covering the entire person
Wound contamination with radioactive shrapnel
With explosion of a Radiological Dispersal Device (Dirty Bomb), radioactive shrapnel or fragments can be propelled through the air and become embedded under the skin or in tissues or organs.
Radioactive material can enter the blood stream or the lymphatics (internal contamination).