Localized relative humidity refers to the relative humidity at your physical workplace location and can vary appreciably from one workstation location to another. This is especially true for large open offices having many workstation locations and poor air circulation as illustrated in FIG. 1.
The localized relative humidity is important because the electrostatic threat level at the workplace location is directly related to the localized relative humidity. An inverse relationship exists between the relative humidity and the electrostatic threat level. The higher the relative humidity (RH) the lower the electrostatic threat level, and the lower the relative humidity the higher the electrostatic threat level, as shown in FIG. 2.
The BumbleBee Models 200 and 300 automatically accommodate changes in the localized relative humidity and adjust the alert timer period accordingly to provide you with sufficient warning to discharge yourself and prevent a catastrophic electrostatic discharge event from occurring. Additionally, Model 300 also displays the localized relative humidity range and the associated threat level associated with the relative humidity.
A major reason for the relative humidity variability is that relative humidity is temperature dependent. An increase in the air temperature lowers the relative humidity, and a decrease in the air temperature increases the relative humidity as shown in FIG. 3.
Another reason for relative humidity variability is that the relative humidity and temperature are usually measured at a single location and not at the individual workstation locations. Maintaining a consistent and equalized relative humidity and temperature for locations remote from a single thermostat location for a large office area is often difficult to achieve.
For example, a first location might be close to an air conditioning vent which would tend to decrease the localized air temperature and increase the relative humidity, versus a second location near an unshaded window receiving full sunlight which would tend to increase the localized air temperature and decrease the localized relative humidity.
Some workplace locations such as individual offices or cubicles may also experience localized heating due to the heat generated from electronic equipment such as computers and displays. Insufficient air circulation may also contribute to an increase in localized air temperature and a decrease in the localized relative humidity. It is well accepted in industry that lower levels of localized relative humidity encourage the accumulation of electrostatic charge which further increases the chances of having a dangerous electrostatic discharge event occur.
The ideal range for minimizing electrostatic charge accumulation is 40 – 60% relative humidity. Maintaining the relative humidity within this range significantly decreases the risk of having a catastrophic electrostatic discharge event occur. For relative humidity levels less than 40%, electrostatic charge accumulation is greatly increased, and for relative humidity levels greater than 60% encourage the growth of mold and may also increase corrosion problems especially for electronic circuits manufactured from copper and silver metals. The United States Occupational Safety and Health Administration (OSHA), recommends office temperatures in the range of 68 – 76 deg F and relative humidity in the range of 20 – 60%.
The BumbleBee Models 200 and 300 constantly measure the localized relative humidity and automatically adjust the period of the alert timer to accommodate any changes in the localized relative humidity, thus always having the proper alert timer period for a given relative humidity as indicated in FIG. 4.
For example, programming the alert timer to automatically self-adjust depending upon the relative humidity level will automatically adjust the alert timer period from 1 minute at a relative humidity range of 0% <= 30% to 3 minutes at a relative humidity range of 40% <= 60%. As the relative humidity level changes within the office area BumbleBee Models 200 and 300 will automatically adjust the period of the alert timer. Additionally, the range of the localized relative humidity is displayed on the RH-LED for the BumbleBee Model 300.