Desiccant (usually indicating silica gel or molecular seive) adsorbs moisture from air inside the desiccator. Some systems include regenerating cycles that bake the desiccant when it becomes saturated. Ideal for low-cost, non-critical applications, but frequent parts access and high regeneration frequency may lead to humidity fluctuations.
Vacuum evacuates air and water vapor; a backfill valve introduces clean, dry process gas (generally nitrogen). Multiple pump/backfill cycles may be required. Achieves very low RH conditions, but requires reinforced chamber (often cylindrical) and vacuum pump.
Uncontrolled cabinets provide a dust-free environment without RH control.
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