Lesson 11 C Use Common Safety and Environmental Procedures Flashcards
Regulations that typically affect PC maintenance or the installation of new equipment are:
- Health and safety laws—Keeping the workplace free from hazards.
- Building codes—Ensuring that fire prevention and electrical systems are intact and safe.
- Environmental regulations—Disposing of waste correctly.
For example, in the United States, the most common safety regulations are those issued by the federal government, such as the Occupational Safety and Health Administration (OSHA), and state standards regarding employee safety.
While specific regulations may vary from country to country and state to state, in general, employers are responsible for providing a safe and healthy working environment for their employees. Employees have a responsibility to use equipment in the workplace in accordance with the guidelines given to them and to report any hazards. Employees should also not interfere with any safety systems, including signs or warnings or devices such as firefighting equipment. Employees should not introduce or install devices, equipment, or materials to the workplace without authorization or without assessing the installation.
ELECTRICAL SAFETY
Electricity flows in a circuit. A circuit is made when conductors form a continuous path between the positive and negative terminals of a power source. An electrical circuit has the following properties:
- Current is the amount of charge flowing through a conductor, measured in amps (A or I).
- Voltage is the potential difference between two points (often likened to pressure in a water pipe) measured in volts (V).
- Resistance is degree of opposition to the current caused by characteristics of the conductor, measured in ohms (Ω or R).
Electrical equipment can give a shock if it is broken, faulty, or installed incorrectly. An electric shock can cause muscle spasms, severe burns, or even death.
Fuses
An electrical device must be fitted with a fuse appropriate to its maximum current, such as 3A, 5A, or 13A. A fuse blows if there is a problem with the electrical supply, breaking the circuit to the power source. If the fuse fitted is rated too low, it will blow too easily; if the rating is too high, it may not blow when it should and will allow too much current to pass through the device.
Equipment Grounding
Electrical equipment must be grounded. If there is a fault that causes metal parts in the equipment to become live, a ground provides a path of least resistance for the electrical current to flow away harmlessly. Devices such as PCs and printers are connected to the building ground via the power plug. However, the large metal equipment racks often used to house servers and network equipment must also be grounded. Do not disconnect the ground wire. If it must be removed, make sure it is replaced by a professional electrician.
Proper Power Handling and Personal Safety
Whenever you add or replace components within a PC or laptop, the power must be disconnected first. Remove the AC plug and also remove the battery if present. Hold down the power button on the device to ensure the circuits are drained of residual power.
PC power supply units can carry dangerously high levels of voltage. Charges held in capacitors can persist for hours after the power supply is turned off. You should not open these units unless you have been specifically trained to do so. Adhere to all printed warnings, and never remove or break open any safety devices that carry such a warning.
Electrical Fire Safety
Faulty electrical equipment can pose a fire risk. If the equipment allows more current to flow through a cable than the cable is rated for, the cable will heat up. This could ignite flammable material close to the cable. If an electrical wire does start a fire, it is important to use the correct type of extinguisher to put it out. Many extinguishers use water or foam, which can be dangerous if used near live electrical equipment. The best type to use is a carbon dioxide (CO2) gas extinguisher. CO 2 extinguishers typically have a black label but sometimes have a red or white label. Dry powder extinguishers can also be used, though these can damage electronic equipment.
You should also ensure that the electricity supply is turned off. This should happen automatically (the fuses for the circuit should trip but may have failed), but make sure you know the location of the power master switches for a building.
Dust Cleanup
Dust is drawn into the computer via ventilation holes. Over time, the dust can form a thick layer over components, heat sinks, fan blades, and ventilation slots, preventing effective heat dissipation. It can clog up peripherals such as keyboards and mice. Dust and smears can make the display hard to read.
To perform dust cleanup:
- Use a compressed air blaster to dislodge dust from difficult-to-reach areas. Take care with use, however, as you risk contaminating the environment with dust. Ideally, perform this sort of maintenance within a controlled work area, and wear an appropriate air-filter mask and goggles.
- Use a PC vacuum cleaner or natural bristle brush to remove dust from inside the system unit, especially from the motherboard, adapter cards, and fan assemblies. Domestic vacuum appliances should not be used as they can produce high levels of static electricity. PC-safe vacuums can often be used to blow air as well as for suction, so they can replace the need for compressed air canisters.
Temperature, Humidity, and Ventilation Control
A computer that is too hot is likely to be unreliable. A computer must be ventilated so that its fans can draw relatively cool air across the motherboard and expel the warmed air from the rear vents. You must ensure that the room (ambient) temperature is not too high and that there is space for air to flow around the case, especially around the ventilation slots. Do not place the computer in direct sunlight or near a radiator.
High humidity—the amount of water vapor in the air—can cause condensation to form. On the other hand, low humidity allows static charges to build up more easily and increases the risk of electrostatic discharge (ESD). The ideal level is around 50%.
Condensation can form because of sudden warming. When installing new equipment that has just been delivered, it is important to leave it in its packaging for a few hours—depending on the outside temperature—to allow it to adjust to room temperature gradually.
Electrostatic discharge (ESD)
Static electricity is a high voltage, low current charge stored in an insulated body. Electrostatic discharge (ESD) occurs when a path allows electrons to rush from a statically charged body to a component that has no charge. This can occur through touch or even over a small gap if the charge is high enough. Static electricity discharged into the delicate structure of electronic devices will flash-over between the conductive tracks, damaging or even vaporizing them. A static discharge may make a chip completely unusable. If not, it is likely to fail at some later time. Damage occurring in this way can be hidden for many months and might only manifest itself in occasional failures.
The human body is mostly water and so does not generate or store static electricity very well. Unfortunately, our clothes are often made of synthetic materials, such as nylon and polyester, which act as good generators of static electricity and provide insulating layers that allow charges to accumulate, especially when walking over carpet. Humidity and climate also affect the likelihood of ESD. The risk increases during dry, cool conditions when humidity is low. In humid conditions, the residual charge can bleed into the environment before it can increase sufficiently to be harmful to electrical components.
Proper Component Handling
Proper component handling tools and techniques protect electronic components against ESD when you service a PC or mobile device:
- If possible, work in an uncarpeted area. Ideally, use an ESD-safe floor or chair mat.
- Touch an unpainted part of a metal computer chassis or power supply case to drain residual charge from your body. This is only a temporary solution, and a static charge could build up again.
- Wear an anti-ESD wrist strap or leg strap to dissipate static charges more effectively. The band should fit snugly around your wrist or ankle so that the metal stud makes contact with your skin. Do not wear it over clothing. The strap ground is made either using a grounding plug that plugs into a wall socket or a crocodile clip that attaches to a grounded point or an unpainted part of the computer’s metal chassis.
- Use an anti-ESD service mat as a place to organize sensitive components. The mats contain a snap that you connect to the wrist or leg strap.
- Handle vulnerable components by holding the edges of the plastic mounting card. Avoid touching the surfaces of the chips themselves.
Proper Component Storage
Electronic components, assemblies, and spare parts are shipped and stored in antistatic packaging to protect them from ESD damage:
- Antistatic bags—This packaging reduces the risk of ESD because it is coated with a conductive material. This material prevents static electricity from discharging through the inside of the bag. These bags can vary in color, such as blue, clear, silver, or pink, and can have a semi-reflective gloss. To protect the contents of the bag fully, you should seal it or at least fold the top over and seal that down.
- Dissipative packaging—This light pink or blue packaging reduces the buildup of static in the general vicinity of the contents by being slightly more conductive than normal. A plastic bag or foam packaging may be sprayed with an antistatic coating or have antistatic materials added to the plastic compound. This is used to package non-static-sensitive components packed in proximity to static-sensitive components.
Faults in building power supply cause
power problems such as surges, brownouts, and blackouts. A range of power protection devices are available to mitigate the faults these power events can cause in computer equipment.
Surges
A surge is a brief increase in voltage, while a spike is an intense surge. A surge or spike can be caused by machinery and other high-power devices being turned on or off and by lightning strikes. This type of event can take the supply voltage well over its normal value and cause sufficient interference to a computer to crash it, reboot it, or even damage it.
Under-voltage event
Devices with large motors, such as lifts, washing machines, power tools, and transformers, require high-starting, or inrush, current. This might cause the building supply voltage to dip briefly, resulting in a under-voltage event. Overloaded or faulty building power-distribution circuits sometimes cause an under-voltage event. An under-voltage event could cause computer equipment to power off.
