For objects that undergo charging to a high potential, the primary impact of humidity is to encourage or discourage corona, and effect the rise time of the discharge current. If the relative humidity decreases, this favorable phenomenon disappears. Even a high relative humidity environment can be susceptible to triboelectric charging. According to Koyler et.al. Also, humidity control may give personnel a false sense of security and cause a relaxation of operator disciplines, thus lowering overall ESD safety.
Humidity control is also expensive and can cause corrosion or other adverse side effects.
Humidity control is a backup that should be implemented only after careful consideration of benefits vs. cost and hazards. An ESD control program should still be employed using conventional grounding, shielding, ionization, and training products and techniques. This is a free monthly newsletter, which specializes on issues in static control in the workplace. This Newsletter is never sent unsolicited. Tell us what you would like to see in future issues.