An absorption badge for passive sampling of aldehydes and ketones in air has been developed. Carbonyl compounds are trapped by reaction with 2,4-DNPH. Separation and quantification of the trapped compounds is performed with HPLC. Preparation and application of the badges for the determination of formaldehyde in air are described. Exposure of the badges to atmospheres with known formaldehyde concentrations show that the amount of formaldehyde trapped by the badge increases linearly for exposure times of 6 to 72 hours, and concentrations in the range of 0 to at least 2500 ppb. The sampling rate of the badge was experimentally obtained as 1.94 ng formaldehyde per ppb per hr, allowing direct calculation of the air concentration from the sampled amount of formaldehyde-DNPH complex on the badge. The detection limit of the HPLC analysis is 0.02 ng formaldehyde in a 10 L injection volume. The sampling detection limit is 2 ppb for a 24 hrs exposure. Results of replicate determinations are both repeatable and reproducible; coefficients of variation are typically less than 10% as long as the air velocity remains constant. The badge provides a simple, cheap and accurate method for sampling of formaldehyde in cabinets, showcases and museum air. -- SCMRE