Introduction and objective:
Many environmental microorganisms live in constant balance between UV damage and repair. The simplest repair process called photoreactivation starts immediately when microbial cells face sunlight irradiation. The aim of the study is to assess the ability of bacteria, virus, and mould suspended in the air and deposited on different surfaces to photoreactivation after their exposure to UV-C radiation produced by two disinfection devices, i.e. low-pressure mercury lamp (LPML) and light-emitting diodes (LEDs).

Material and methods:
Five microbial strains (Staphylococcus aureus ATCC 6538, Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa ATCC 260, Aspergillus versicolor ATCC 9577, and bacteriophage PhiX174 ATCC 13706-B1) deposited on metal, plastic, and glass surfaces, as well as dispersed in the air as bioaerosols, were irradiated with high UV-C doses (762 J/m2 and 832 J/m2), and subsequently exposed for 24 h to visible light with a wide (380–780 nm) spectral range to check their ability to photorecovery.

Results:
UV-C radiation emitted by LPML and LEDs effectively inactivated the tested microorganisms deposited on metal, plastic and glass surfaces, as well as dispersed in the air. However, this type of inactivation is not an irreversible process and subsequent exposure of microbiologically contaminated elements of the environment with visible light may partially rebuild the population of pathogenic microorganisms in photoreactivation process.

Conclusions:
Effective cleaning of both the surfaces and air cannot be limited to their exposure to UV-C radiation, but should be supplemented with other techniques for neutralizing microorganisms, which need be subsequently applied after such exposure.