At low concentrations, formaldehyde causes nausea, irritation of eyes, respiratory tract and skin. Inhalation of formaldehyde at high concentrations causes severe irritation of the respiratory tract. However, the most important toxicity characteristic is its official consideration of carcinogenicity by both the European Union and the WHO expert group.
For interior spaces, the optimum value should be 0.0 ppm. Fortunately, Formaldehyde is regulated in some of the aforementioned products, although buildings with high levels of formaldehyde are still found for different causes.