UV-C light is automatically absorbed by micro organisms (bacteria, moulds, etc.). The goal is to have the UV-C light penetrate the organism and destroy it’s DNA from inside, so the organism is cracked and inactivated.
While all micro organisms are sensitive to UV-C light, the degree of sensitivity is dependant on their structure (core, cell wall, pigments, etc.). The less barriers the UV-C light needs to pass, the easier the UV-C light can disrupt the micro organism’s DNA. So, the structure of the organism is the deciding factor of the UV-C radiation dosage.
For organisms with high UV-sensitivity, the applied UV dosage is low, and vice-versa. Every micro organism has its own distinctive disinfection dosage. The dosage is shown in Joule per m2 (J/m²), millijoule per cm2 (mJ/cm²) or Watt Second per m2 (W s/m²).