Glutaraldehyde has been in widespread use in hospitals to sterilize instruments. Routine exposure to glutaraldehyde is, however, known to cause adverse health effects. Authors have applied and evaluated a passive sampler (DSD-DNPH) for the determination of glutaraldehyde in air at ppb level. The sampler consists of porous polyethylene tube uniformly packed with 2,4-dinitrophenylhydrazine (DNPH) coated silica gel as a reactive adsorbent. The sampling duration of this device was designed for 8 hr to apply to field measurements in workplace. After sampling, DNPH derivatives were eluted by acetonitrile and subsequently determined by HPLC. A sampling rate of the sampler was determined by chamber experiments and resulted in 40 ml/min for glutaraldehyde. Effects of temperature and humidity on the rate were not apparent. No significant effect of exposure time, air concentration and back diffusion on the sampling performance was suggested by dynamic adsorption model. The sampling rate was then validated in field measurements comparing with a previous active sampling. The diffusion sampler was successfully used for determination of 4-180 ppb of glutaraldehyde and gave similar results to active sampling in indoor air. Limit of quantitation (LOQ) of the diffusion sampler resulted in 3.9 ppb for 8-hr exposure in air.