Safety Issues

When working on computers it's important to pay attention to safety considerations. A basic premise to always keep in mind is that computers are just things that can be replaced, but we can't replace people. In others words, value people first when working with computers. By following basic precautions, you can prevent damage to people and to equipment.

Electrical Safety

Unless you're measuring voltages withn a computer, you should never work on computers without first removing power. This includes turning the computer off and unplugging it.

Just turning off the power is not enough. ATX-based power supplies provide power to the motherboard even if the front power switch on the computer indicates that it is turned off. If you want to ensure that the computer does not have any power, unplug the power supply.

Most people consider PSUs modular units. In other words, if the PSU fails you simply replace it instead of trying to repair it. However, if you do open the power supply, don't forget the following two important warnings:

o Never open it when it is plugged in.

o Even after you unplug it, capacitors within the power supply will hold a charge. If you touch the capacitor, it can easily discharge and shock you. I learned this lesson first-hand when playing with one of my radio sets when I was about eight years old. It knocked me against the wall and left my mother white-faced for quite a while.

Equipment and Self-Grounding

In electronics ground refers to a path to Earth. A copper cable is attached to a spike and hammered into the ground. The other end of this cable is available in the electrical system and identified as a ground. Most electrical equipment includes circuitry that will automatically redirect any dangerous voltages to ground to prevent shocks.

IMPORTANT EQUIPMENT GROUND CONNECTIONS SHOULD ALWAYS BE CONNECTED

Disconnecting ground connections can bypass safety circuits. Dangerous voltages can be redirected tom the computer case, resulting in a shock if a user touches the case.

Ground is referred to differently based on the location of the connection. For example Figure 1-9 shows the three primary symbols used for ground.

Earth ground is the path directly to Earth. Chassis ground refers to tje path to the equipment case or chassis. Signal ground refers to the return path for a signal. Signal ground connections are commonly connected to the chassis. For example, some screws connecting a motherboard to a computer case connect the motherboard ground to the case. The chassis ground is then connected to the Earth ground via the power cable.

ESD

Static electricity builds up on different types of objects, and when one object touches another, the static discharges. You've probably experienced a static discharge after walking across a carpeted floor and touching a doorknob. This is also called electrostatic discharge (ESD).

The shock you felt might have been unpleasant, but it wasn't harmful. However, it can be damaging to computers. If you felt it, at least 3,000 volts were discharged from your hand to the doorknob. If you actually saw the spark when it discharged, it was at least 8,000 volts. The good news is these voltages won't kill or hurt people, mostly because they aren't combined with current to generate power.

O Use an ESD wrist strap. An ESD wrist strap wraps around your wrist and has a metal component touching your skin. A wire leads from the strap to an alligator clip that you can clip to the computer case. This results in you and the case being at the same potential, and it prevents static discharge. On work benches, ESD straps are used to connect the equipment case to a grounding bar that vis connected to Earth ground. The technician can connect alligator clips from the wrist strap to the case or to the grounding bar.

o Use antistatic bags. When storing and transporting electronic components, they should be stored in antistatic bags. These bags help prevent static from building up and causing ESD damage to the components.

o Use ESD mats. Special mats prevent static buildup, and they are commonly used on work benches. Technicians place computers on the antistatic mat while working on them. Larger antistatic mats can be placed on the floor in front of the technician's bench to reduce static.

Exam Tip

Very small amounts of ESD can cause damage. This is especially true when handling sensitive components such as CPU's and memory. ESD protection such as antistatic wrist straps, antistatic component bags, and antistatic mats are valuable to protect against ESD damage when handling CPU's, memory, and other sensitive components.

o Self-grounding. If you touch the computer case before working on any components, built-up static will discharge harmlessly onto the case. This ensures that your body is at the same ground potential as the case. Additionally, if you keep your feet stationary after touching the case, it reduces the chances for static to build up.

Don't touch components or pins. If you remove any circuit cards, don't touch the components or the pins. Instead, hold the outside edges or plastic handles.

Control humidity. When the humidity is very low, static builds up more quickly. If you live in a colder area, you'll notice that static is more common in the winter because heating systems remove humidity from the air. In contrast, when the humidity is higher, the static charges dissipate naturally. Ideally, humidity should be around 50 percent.

Don't place computes on carpets.

Static can build up on carpets more easily than on other floor surfaces. You've probably noticed that in a heated building you can shuffle your feet over a carpet to quickly build up static. This doesn't work on tile floors or other floor surfaces.

MSDS

Material Safety Data Sheets (MSDS) are available for most products that have a potential to cause harm to people or equipment. This includes materials such as cleaning solutions, paints, and chemicals. The MSDS identifies important safety facts about the material including its contents, its characteristics, how to handle and store it safely, and how to dispose of it. It will also list first-aid steps to take if the material presents a danger.

As an A+ technician, you are likely to use products that have MSDS sheets. For example, you might use cleaning products that clean computer screens or keyboards. If any of these products is causing an adverse reaction to either people of the equipment, you can refer to the MSDS sheet for information about the product and additional steps to take after the exposure.

Compliance with Regulations

Any government regulations pertaining to safety or environmental controls must be followed. For example, the state of California has mandated that all batteries be disposed of as a hazardous waste. Even if the batteries are the newer mercury-free alkaline batteries, the regulation still requires special handling.

NOTE IGNORANCE IS NO EXCUSE

An old saying related to the law is that "ignorance is no excuse." With that in mind, organizations have a responsibility to learn what regulations apply to them where they operate, and to comply with those regulations.

Fire Safety

Fires are classified based on what is burning, and fire extinguishers are classified based on what fires they can safely extinguish. The four primary types of fires are aa follows:

o Class A. This type of fire involves ordinary combustible material such as paper and wood. The fire can be extinguished with water or a Class A fire extinguisher.

o Class B. This type of fire involves flammable liquids and gases. Class B fire extinguishers use chemicals to disrupt the chemical reaction, or they smother the fire with a gas such as carbon dioxide. Spraying water on a class B fire is dangerous because it will spread the fire instead of extinguishing it.

o Class C. An electrical fire is a Class C fire, and the best way to extinguish it is by removing the power source. For example, unplugging it or turning off the circuit breaker can stop the fire. Class C fire extinguishers use special chemicals such as Purple-K or carbon dioxide to extinguish a fire.

IMPORTANT NEVER USE WATER TO EXTINGUISH CLASS C FIRES

o Class D. This type of fire involves combustible metals. A Class D fire extinguisher uses special chemicals to smother the fire. Water should not be used.

Lifting

When lifting equipment, it's best to lift with your legs, not your back. In other words, instead of bending down to pick up heavy equipment, you should squat, bending your knees, to pick it up.

There aren't any firm guidelines on safe weight limitations. However, it's generally recommended that individuals do not try to lift equipment weighing more than 70 pounds without help.

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