The passive adsorbent dosimeter (PAD) is a critical component in the man-in-simulant-test (MIST). It is the only approved device for use in determining the localized and systemic protection factors for chemical protective ensembles. In MIST evaluation protocols, PADs are placed on test subjects underneath the protective suit, and then the test subject is exposed to a known concentration of methyl salicylate (MeS), a warfare agent simulant. The purpose of the PADs is to collect the MeS vapors that enter the suit at seams, closures, or interfaces between the protective suit and gloves, boots, or the breathing apparatus. Given this key role, it is imperative that the diffusive uptake rates associated with the PADs are characterized. It is equally important to fully understand the factors influencing these rates. This research investigates two different categories of influential factors: the variation in adsorption rates associated with the simulant concentration and exposure time, and the relation to the effect of the time and temperature of the PAD's storage prior to extraction and analysis. For the first study, PADs were exposed, in the full scale MIST Facility at North Carolina State University, to concentrations ranging from 15 to 100 mg/m3 for exposure times ranging from 1 min to 2 h in duration. In the second study, the effect of the storage time prior to analysis was determined by exposing PADs at a set condition and varying the amount of time before the PADs were extracted. In order to assess the effects of storage temperature on the uptake rate, PADs were exposed and stored at temperatures ranging from below −30°C to 4°C. The findings of this research help identify and explain a possible source of differences that have been observed in MIST results at different testing sites. This work also provides a deeper understanding of the characteristics of the PADs themselves.