Humidification

DOE-HDBK-1092-2004

location. Instruments used in testing shall be used only when the room is free from exposed

explosives and mixtures of flammable gases.

Maximum floor resistance shall be measured with a suitably calibrated insulation resistance

tester that operates on a normal open-circuit output voltage of 500 V dc and a short-circuit

current of 2.5 mA with an effective internal resistance of approximately 200,000 ohms. Minimum

floor resistance shall also be measured with a suitably calibrated ohmmeter.

Each electrode shall weigh 2.3 kg and shall have a dry, flat, circular contact area 6 cm in

diameter, which shall comprise a surface of aluminum or tinfoil 1.3 to 2.5 mm thick, backed by a

layer of rubber 0.6 to 0.65 cm thick, and measuring between 40 and 60 durometer hardness as

determined with a Shore Type A durometer.

The floor shall be clean and dry. Only electrode jelly shall be used to establish a good contact.

(Brushless shaving soap and saline solution shall not be used.)

The resistance of the floor shall be more than 5,000 ohms in areas with 110-V service, 10,000

ohms in areas with 220-V service, and less than 1,000,000 ohms in all areas, as measured

between a permanent ground connection and an electrode placed at any point on the floor and

also as measured between two electrodes placed 3 ft apart at any points on the floor.

Measurements shall be made at five or more locations in each room. If the resistance changes

appreciably during a measurement, the value observed after the voltage has been applied for

about 5 sec shall be considered the measured value. (See Figure 5-1.)

Figure 5-1. Testing shoes on wearer.

5.1.4.6 HUMIDIFICATION

Humidification to prevent accumulations and subsequent discharges of static electricity is

usually effective if the relative humidity is above 60 percent. However, certain materials such as

metallic powders and some pyrotechnic mixtures cannot be exposed to air with 60 percent

5-4