Effective removal of formaldehyde has become a focus in the field of indoor air quality. The degradation performance of low-concentration gas formaldehyde by titanium dioxide has been studied in a photocatalytical reactor(PCR) under UV irradiation and a small-scale environmental chamber under fluorescent lamp, respectively. Experimental results show that it takes long time to photodegrade formaldehyde at the experimental conditions and that the degradation efficiency is not high, 77.3% in the reactor and only 33.3% under fluorescent photocatalysis in the chamber. Besides of carbon dioxide, carbon monoxide is also found to be one of the byproducts in the photocatalytic process. The intermediates can not be ignored because they can occupy the active sites of catalyst, leading to the deactivation of the catalyst. The concentration of carbon dioxide and carbon monoxide in gas phase may be even higher than that of formaldehyde if there is much pre-adsorbed formaldehyde in equilibrium before illumination. The ratio of concentration of carbon monoxide to concentration of carbon dioxide ranges between 0.7% and 4.1% during the photodegradation in the reactor, and between 0.1% and 0.6% in the chamber.
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