Why UV lights are not used for sterilization?

In Microbiology, there is great importance of UV lights. UV lights are available in pass boxes, laminar air flow benches, biosafety cabinets etc. There is a misconception that UV lights are used for sterilization of material kept inside pass box, laminar air flow bench or biosafety cabinet. UV lights are only used for surface decontamination not for sterilization. 

                                                        UV Light

Here surface decontamination means, removal of bio-load/contamination from the surface only which is in direct contact with the UV light but sterilization means complete removal of all form of microorganisms from the surface or inside the material. UV light can only kill the microbes present on surface because penetration power of UV light is low so it is not able to penetrate inside the material in order to sterilize them. Sterilization can be done by moist heat, dry heat, chemical treatment, gas sterilization etc. In sterilization, sterilant penetrate inside the material or article and kill all forms of living microbes present on surface and inside the material. 

Conclusion: UV light is only used for surface decontamination not for sterilization