Indoor formaldehyde in real buildings: Emission source identification, overall emission rate estimation, concentration increase and decay patterns

• A source identification and overall emission rate estimation method was introduced.
• The results confirm that natural ventilation can quickly remove indoor contaminants.
• The time scale of concentration increase is much bigger than that of decay patterns.

Formaldehyde is a commonly observed indoor air contaminant with proved health effects. For the control of indoor formaldehyde, quick methods applicable in actual buildings are needed to identify the emission sources and estimate overall emission rates. The concentration decay and increase patterns with windows open or closed must also be studied to devise control strategy guidelines for natural ventilation in buildings. In this paper, a quick and easy-to-use method was introduced to identify the emission sources and estimate the overall emission rate resulting from all the emission sources. The method was applied to an apartment unit with multiple formaldehyde sources and showed promising applicability. The formaldehyde concentration decay patterns with different window opening degrees were measured and compared with the concentration increase patterns with closed windows. The results confirmed that natural ventilation through window opening can quickly remove indoor contaminants, and that the time scale of formaldehyde concentration increase is much bigger than that of decay patterns. The results imply that in control of indoor contaminant, natural intermittent ventilation by opening and closing windows is applicable.