Safety is a subject of utmost importance to all technical personnel. Potentially hazardous situations
exist in almost any work area. The disregard of safety precautions can result in personal injury or in the
loss of equipment or equipment capabilities.
In this section we will discuss two types of safety factors. First, we will cover damage that can occur
to electronic components because of electrostatic discharge (ESD) and improper handling and stowage of
parts and equipment. Second, we will cover personal safety precautions that specifically concern the
Electrostatic discharge (ESD) can destroy or damage many electronic components including
integrated circuits and discrete semiconductor devices. Certain devices are more susceptible to ESD
damage than others. Because of this, warning symbols are now used to identify ESD-sensitive (ESDS)
items (figure 3-31).
Figure 3-31.Warning symbols for ESDS devices.
Static electricity is created whenever two substances (solid or fluid) are rubbed together or separated.
This rubbing or separation causes the transfer of electrons from one substance to the other; one substance
then becomes positively charged and the other becomes negatively charged. When either of these charged
substances comes in contact with a conductor, an electrical current flows until that substance is at the
same electrical potential as ground.
You commonly experience static build-up during the winter months when you walk across a vinyl or
carpeted floor. (Synthetics, especially plastics, are excellent generators of static electricity.) If you then
touch a door knob or other conductor, an electrical arc to ground may result and you may receive a slight
shock. For a person to experience such a shock, the electrostatic potential created must be 3,500 to 4,000
volts. Lesser voltages, although present and similarly discharged, normally are not apparent to a person's
nervous system. Some typical measured static charges caused by various actions are shown in table 3-2.