Risk assessment for indoor formaldehyde and other carbonyls was investigated at an university in Xi’an, Shaanxi, China. Eight representative locations, including six indoor workplaces and two residential units of staff apartments and a student dormitory, were chosen. The indoor pollution origins were identified according to the variability in molar composition and correlation analysis for the target species. Environmental tobacco smoke (ETS), cooking activities, and office technologies such as printers and copiers can produce different degrees of carbonyls in the workplace. A one-year demonstration study conducted in a apartment showed significance of the off-gases from lacquers and new wooden furniture. The concentrations of formaldehyde and acetaldehyde in the most sampling locations were above the recommended exposure limits, reflecting a potential health risk to workers and occupants. Chronic daily intake (CDI) and lifetime cancer hazard risk (R) were calculated to assess the carcinogenic risks of chronic exposure to the carbonyls. The R values for formaldehyde exceeded the alarm level of 1 × 10–6 in all sampled workplaces, but lower R values were associated with acetaldehyde. The results indicate that exposure of formaldehyde is a critical occupational health and safety concern. In addition, high risks associated with formaldehyde were also measured in the staff apartment, suggesting that the refurbishing materials and wooden furniture can potentially cause health impacts to occupants. The findings are informative to be referred in establishment of indoor air quality guidelines in China.