This paper compares two different housing systems for laying hens producing table eggs, namely a conventional cage system and an aviary, during three summer months, starting from the 20^th week of the production cycle. Research was focused on airborne bacteria, fungi and dust levels and on the bacterial eggshell contamination. Levels of airborne bacteria determined in the aviary system were many times higher and ranged from 6.2 × 10⁴ CFU/m³ to 8.9 × 104 CFU/m3, and the levels of airborne fungi ranged from 1.6 × 10⁴ to 1.9 × 104 CFU/m³, while the levels of airborne bacteria and fungi determined in the conventional cage system ranged from 1.6 × 10⁴ to 2.5 × 10⁴ CFU/m3 and from 0.8 × 10⁴ to 1.3 × 10⁴ CFU/m³, respectively. Microbial air contamination was associated with eggshell contamination, with the levels in the aviary ranging from 5.4 × 10³ to 9.6 × 103 CFU/eggshell and those in the conventional cage system ranging from 2.3 × 10³ to 3.6 × 10³ CFU/eggshell. Airborne dust levels in the aviary and conventional cage system ranged from 3.2 to 4.6 mg/m³ and from 0.7 to 1.2 mg/m³, respectively. From the aspect of animal welfare and behavioural requirements, alternative systems, i.e. aviaries, appear more acceptable; however, they are not satisfactory from hygienic aspects because of a higher content of airborne pollutants which can represent a greater risk of horizontal contamination of the egg content.