Control of RH in a Desiccator
Two Petri dishes filled with 20 mL of salt solution (either potassium acetate, potassium carbonate, cobalt (II) chloride, or potassium chloride) or double distilled water were placed in a desiccator [23], [24]. Air circulation inside the desiccator was enhanced by a fan to accelerate the establishment of equilibrium RH between the salt solution and the air inside the desiccator. Before each experiment began, the desiccator was conditioned to the desired RH. The desiccator had to be opened briefly to insert the samples, and the system reestablished equilibrium within ∼10 min. The actual RH and temperature inside the desiccator were recorded at 1-min intervals during sampling with a temperature/humidity logger (OM-73, Omega Engineering, Inc., USA). RHs tested in model media included 17.5±1.0%, 27.6±0.9%, 42.0±0.8%, 44.1±1.2%, 50.2±0.7%, 59.5±1.1%, 76.1±0.7%, 84.1±0.8%, and 98.9±0.4%. RHs tested in mucus included 26.7±0.8%, 40.3±1.1%, 48.0±1.2%, 52.0±0.9%, 60.8±1.1%, 72.2±1.2%, 83.9±0.4%, and 99.1±0.4%.