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2012-06-18

A+: Hazards

Computers and their peripherals can kill or injure you if you don’t take reasonable precautions. Here we discuss computer maintenance and the precautions you can take against these dangers.

Computer equipment and supplies can pose a number of potential hazards for the technician (and, in some cases, for computer users):

    • High voltage sources, such as computers, and peripherals, such as printers and monitors
    • Mechanical devices, such as printer mechanisms
    • Power or data cables running across floors or other locations where users could trip and fall
    • Liquids, such as those used for cleaning or refilling inkjet cartridges
    • Situational hazards, such as unsafe temporary equipment or cabling locations
    • Atmospheric hazards, such as those created by the use of toxic cleaners or the discharge of computer-room-rated fire suppression chemicals
    • Moving heavy equipment, such as laser printers, servers, large UPS systems, or print/scan/copy devices.


Computers and their peripherals can kill or injure you if you don’t take reasonable precautions. Here we discuss computer maintenance and the precautions you can take against these dangers.

Computer equipment and supplies can pose a number of potential hazards for the technician (and, in some cases, for computer users):

    • High voltage sources, such as computers, and peripherals, such as printers and monitors
    • Mechanical devices, such as printer mechanisms
    • Power or data cables running across floors or other locations where users could trip and fall
    • Liquids, such as those used for cleaning or refilling inkjet cartridges
    • Situational hazards, such as unsafe temporary equipment or cabling locations
    • Atmospheric hazards, such as those created by the use of toxic cleaners or the discharge of computer-room-rated fire suppression chemicals
    • Moving heavy equipment, such as laser printers, servers, large UPS systems, or print/scan/copy devices


High Voltage Hazards

The number-one hazard created by computer equipment is high voltage that can be present while devices are turned on and plugged in and even when some devices are unplugged and turned off. The major sources of potentially dangerous voltage include

    • Printers
    • Power supplies
    • Monitors
    • Systems in suspend or sleep modes

Printers also pose laser and mechanical hazards to technicians.

Printers

Unlike computers, printers normally do not run on safe, low-voltage DC (direct current). Although laser printers typically do use DC current, it is at a high voltage. Most impact and inkjet printers also use high-voltage AC (alternating current).

Any printer should be turned off and unplugged before being serviced. In the event of ink or toner spills, water or other liquids should not be used to clean up the mess unless the printer is turned off and disconnected, due to the risk of a potentially fatal electric shock.


The Power Supply

The exterior of practically every power supply is marked something like this:

CAUTION! Hazardous area! Severe shock hazards are present inside this case. 
Never remove the case under any circumstances.

Believe it. You can see the danger if you understand what is in the “cage” at the back of the typical power supply. Past the cooling fan it contains, you’ll see coils of heavy wire. These windings retain potentially lethal high voltage levels for a long time.

    Because any power supply you buy as a replacement is likely to have a higher wattage rating and can also have a quieter fan than your current power supply, don’t go cheap and wind up dead. Heed the warnings and replace the power supply without opening it to find out why it is broken. Make sure you purchase a UL-rated power supply.

CRT Monitors

As with the power supply, the outside of the monitor is safe. However, if you remove the cover of a CRT monitor for servicing or adjustments, you expose the danger. The high voltage anode (a metal prong covered with a red insulator, found on the wide top of the CRT) holds dangerously high voltage for days after the power is turned off.

Disassembled CRT monitors also pose the following hazards: X-rays coming from the unshielded neck of the CRT when the monitor is on, and dropping the monitor and breaking the CRT.

Replace the shielding around the neck of the CRT before using the monitor, and use padding and carefully balance CRTs and monitors during storage and transport to avoid damage.


Systems in Suspend Mode

Systems based on the ATX, BTX, or NLX standards typically go into a deep suspend mode rather than a true “off” condition when shut down by Microsoft Windows. Some ATX and BTX systems have power supplies with a separate on/off switch on the back of the unit, but some do not. For these reasons, you should disconnect the power cord from the system to avoid potentially lethal electric shock.

As with other devices, the power can be on unless you disconnect it at the source.

Precautions Against Electric Shock

This section discusses the precautions you should take to avoid the hazards covered in previous sections.

To work with electricity safely, follow these simple precautions:

    • Remove jewelry, including rings, bracelets, and necklaces. Metal jewelry provides an excellent path for current.

    • Use rubber gloves for extra insulation—rubber gloves prevent your hands from touching metal parts; however, they do not provide sufficient insulation to enable you to work on a live system.

    • Work with one hand out of the system if possible, to avoid electricity passing through your chest if your arms complete a circuit.

    • Keep your hands and the rest of your body dry; your body’s natural shock resistance drops to virtually nil when your skin is damp.

Regardless of the level of service you will provide to a component, devices such as printers, computers, monitors, and so on should be disconnected from power as well as turned off before service. This will help prevent shock hazards as well as mechanical hazards.

Do not leave the computer plugged in while you work inside it. At one time, an acceptable practice was to leave the computer plugged in but shut down and keep one hand on the power supply as a ground. This is no longer appropriate because ATX, BTX, and other modern computers aren’t really “off”; they’re in a suspend mode and power is still running through memory, expansion cards, and so on.


Discharging CRTs

Do not service CRT-based monitors as a first choice today; most companies are rapidly replacing their remaining CRTs with LCD displays to save power and desk space. You should not service any monitor unless you are a certified CRT technician. However, if you must open a CRT-based monitor for service, discharge the high voltage anode following this procedure:

    Step 1. Turn off and unplug the monitor.

    Step 2. Remove the housing carefully.

    Step 3. Attach a large alligator clip and wire from a long, flat-bladed, insulated screwdriver to the metal frame surrounding the monitor.

    Step 4. Slide the flat blade of the screwdriver under the insulator until the tip touches the metal anode clip

    Step 5. Be prepared for noise—anything from crackling to a loud pop—as the anode discharges its stored electricity. Keep the screwdriver in place for several seconds to fully discharge the anode.

    Step 6. Slide the screwdriver out without twisting it; you could damage the CRT.

This process must be repeated after each time the monitor is powered up until the housing is replaced.

Mechanical Hazards

Although computers and their peripherals are primarily electronic and electrical devices, they can pose various mechanical hazards to users, including

    • Impact and inkjet printers can pinch or crush fingers in their gears and paper feeders if the cover is removed while the printer is in operation.

    • CD and DVD trays can pinch fingers or damage cables when retracting.

• Pins in serial, parallel, VGA, and DVI cable connectors can cause puncture wounds.

    • Sharp edges on metal computer cases, card brackets, and drive rails can cause minor cuts.

To avoid mechanical hazards like these, take the following precautions:

    • Turn off printers before attempting to remove paper or label jams.

    • Follow the manufacturer’s recommended procedure for changing ink cartridges to prevent the printer from attempting to print, move the printhead, or advance paper during the process.

    • Make sure fingers, cables, and other potential obstructions are out of the way before closing CD and DVD trays.

    • Don’t touch the pins in cable connectors to avoid potential harm to yourself or ESD risks to connected equipment.

    • Handle chassis components such as computer cases, card brackets, and drive rails with care. Avoid sliding your hands along the edges of these and similar sheet-metal parts to avoid cuts and scrapes.

    • Have antibiotic ointment and appropriate bandages, including finger and knuckle bandages, handy in case of injury to hands or fingers.

Tripping Hazards

Watch out for loose cables! Whether it’s a temporary setup while you are repairing a balky PC or printer or a “permanent” office setup, power or data cables running across floors or other locations where users could trip and fall are accidents waiting to happen. When someone trips or falls because of power or data cables, both the individual and the connected equipment can be harmed.

Avoid trip/fall hazards by controlling cable sprawl. Use the following tools and techniques to manage cables:

    • Cable ties are an inexpensive way to keep overlength cables out of the way. They use Velcro or similar hook-and-loop material to provide self-adhesive properties, and come in a variety of colors you can use for color-coding or to assure that the cable tie is the same color as or a contrasting color to the cable. Cable ties are available at electronics and computer stores, as well as fabric and hobby stores.

    • To manage bundles of cables running to a particular PC or other equipment, consider cable wraps or cable trappers.

    • For temporary cable runs across floors, such as in a repair situation, a trade show, or a training class, use gaffers’ tape or duct tape to tape the cables to the floor. These types of tape leave little or no residue when used for short periods of time and can be used to hold down network, power, video, or other types of cables.

    • For long-term cable installations, use cable management systems to keep cables out of the way. These can be as simple as a floor cable concealer, which protects cables on the floor from damage, or as elaborate as cable trays, which carry cables over a suspended ceiling, or cable raceways, which conceal cable runs along wallboards or crown molding. The Cable Organizers website, www.cableorganizer.com, is a good place to start your search for permanent cable organizing solutions.

Liquid Hazards

Liquids, such as those used for cleaning computer equipment or refilling inkjet cartridges, pose a variety of hazards, including electric shock hazard when used to clean ink or toner spills in a printer, and carpet or clothing stains when refilling inkjet cartridges.

To avoid electric shock hazards caused by liquid cleaner, make sure the printer or other component is turned off and unplugged before using a liquid cleaner. To clean up spilled toner, use a toner-rated vacuum cleaner.

To avoid carpet or clothing stains when refilling inkjet printer cartridges, be sure to follow the vendor’s instructions carefully.


Situational Hazards

When you are setting up computer equipment on a temporary basis, such as for a repair or configuration before permanent installation, it might be tempting to take shortcuts that you would not consider for a permanent installation. Watch out for the following:

    • Don’t overload a worktable or bench with equipment. If the legs collapse or the tabletop gives way, both you and the equipment could be harmed. Check the rating for the furniture before piling it up with heavy printers, UPS systems, all-in-one units, 19-inch or larger CRT monitors, and similar heavyweights.

• Avoid using chairs, tables, or other surfaces as replacements for stepstools or ladders. You can fall and hurt yourself—and break equipment in the process.

    • Don’t use empty boxes as temporary stands for equipment. If you must use boxes until the furniture arrives, use boxes that still contain equipment—and don’t put heavy components atop lightweight boxes.

    • Watch out for trip/fall hazards from power and data cables, surge suppressors, and the like. See “Tripping Hazards,” earlier in this chapter, for methods to avoid tripping hazards during short-term computer setups.

Situational hazards can also pose potential threats during permanent computer or peripheral installation:

    • Don’t overload tempered-glass desktops or other furniture. These items usually have clearly-marked load limits. Exceed them, and watch the monitors or printers crack the glass as they fall.

    • Tag power and data cables to make it easy to tell which cables go with what equipment.

Atmospheric Hazards

The major atmospheric hazard for computer users is the use of Halon in the fire-extinguisher systems of computer rooms. Halon is toxic to humans (it can cause cardiac problems), although it is safe for computer equipment. If you work in a computer room or other area that uses Halon-based fire extinguishers or sprinkler systems, make sure you do not breathe in Halon fumes. Exit the area immediately in case of fire.

DuPont FE-36 is a safe alternative to Halon, providing comparable fire suppressant control for Class A, B, and C fires, while being far less toxic. To learn more about FE-36, see the DuPont FE-36 information page at http://www2.dupont.com/FE/en_US/products/fe36.html.

Heavy Equipment Hazards

Laser printers, workgroup-grade all-in-one units, high-capacity UPS battery backup systems, and servers are potential hazards because of their weight and bulk. Take the following precautions to avoid injury and damage

    • Move equipment in its original cartons and packaging whenever possible.
    • Use wheeled freight dollies or carts to move equipment.
    • Use “team lift” methods to move heavy and bulky items.
    • Wear a back brace.


Environmental and Accident Incident Handling

Even with the best of precautions, environmental issues and accidents involving computers and related technologies can and do happen. Use the following procedures to handle problems safely and professionally

    • Know who to contact in case of injuries to personnel, damage to equipment, fires, or chemical spills.

    • Know how to reach an outside phone line to call 911 in case of serious emergency.

    • Review and follow procedures for cleaning up chemical spills, retrieving damaged computer equipment, or other problems.

    • Have MSDS information available for computer-related supplies and chemicals.

    • Write up the incident in a professional manner, noting time, place, personnel involved, and other important information.

    • Work with other personnel to solve problems resulting from the incident.

    • Learn from the incident to help avoid future problems.


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