Introduction: The study aimed at determination of the usefulness of the subjective assessment of selected signs of fungi growth in flats and microclimate parameters to indicate the actual air contamination with culturable fungi, (1→3)-β-D-glucans and fungal spores. Material and methods: This analysis covered 22 flats, the inhabitants of which declared in a questionnaire interview the presence of the developed mycelium on solid surfaces in the flat. Air samples for determination of the culturable fungi, (1→3)-β-D-glucans and (viable and non-viable) fungal spores concentrations indoor and outdoor the flats during the heating period were collected. During bioaerosol sampling microclimate parameters were measured. Predictive models for concentrations of the tested biological agents with regard to various ways to assess fungal contamination of air in a flat (on the basis of a questionnaire or a questionnaire and microclimate measurements) were built. Results: The arithmetic means of temperature, relative humidity, CO₂ concentration and air flow velocity in the flats were respectively: 20.5°C, 53%, 1431.6 ppm and 0 m/s. The geometric mean concentrations of airborne fungi, (1→3)-β-D-glucans and fungal spores in these premises amounted to 2.9×10² cfu/m³, 1.6 ng/m³ and 5.7×10³ spores/m3, respectively. The subjective assessment of fungi growth signs and microclimate characteristics were moderately useful for evaluation of the actual airborne fungi and (1→3)-β-D-glucan concentrations (maximum percent of explained variance (VE) = 61% and 67%, respectively), and less useful in evaluation of the actual fungal spore concentrations (VE < 29%). In the case of fungi, higher usefulness was indicated of the questionnaire evaluation supported by microclimate measurements (VE = 61.2%), as compared to the evaluation only by means of a questionnaire (VE = 46.9%). Conclusions: Subjective evaluation of fungi growth signs in flats, separately or combined with microclimate measurements, appeared to be moderately useful for quantitative evaluation of the actual air contamination with fungi and their derivatives, but more extensive studies are needed to strengthen those findings.