General Safety Warnings (All Devices)
Use Good Judgment and Common Sense
Use these instructions as a starting point, but remember that every device is different. Keep an eye out for any possible safety hazards that might be unique to your situation.
- Plan your project carefully. Try to anticipate potential hazards, and take steps to avoid them.
- If you feel less than 100% safe performing any aspect of a repair, stop working immediately and ask for help.
- Don't work alone. In the event of an emergency, it's important to have someone on hand to help or call 911.
Disconnect All Power Sources Before Opening Your Device
Never work on anything that is plugged in to a power outlet.
- The device should be physically unplugged, not just “switched off.”
- Whenever possible, remove the battery or batteries before beginning disassembly.
Watch Out for Large Capacitors
Big capacitors (the kind most likely to be dangerous) are usually cylindrical and look roughly like battery cells.
- Assume they are charged until you've confirmed they are discharged.
- Use an appropriate tool to discharge and/or ground large capacitors, while keeping yourself well insulated and at a safe distance.
- When discharging large capacitors, use only one hand, and keep the other hand behind your back or in your pocket. This prevents you from inadvertently completing a circuit with your second hand and creating a path for electric current to travel through your heart.
- Wear rubber-soled shoes.
- Wear eye protection. A stray spark can cause severe eye damage.
- Remove all rings, bracelets, necklaces, etc. before working on devices with large capacitors.
Be Mindful of Moving Parts
Large, mechanical devices such as bicycles or cars contain many moving parts that can pose a safety hazard, particularly when repairs are being performed.
- Any given part’s range of motion may change suddenly while you are working on it. Position yourself so that if a heavy or potentially dangerous part moves unexpectedly, you will not be injured.
- Wear protective gloves.
Avoid Heavy Metal Toxicity
Printed circuit boards in older electronics may contain toxic heavy metals such as lead and mercury. Wash your hands thoroughly after you finish and before you eat. Don't eat or drink while handling electronic components.
Safety For Your Readers
When creating your guides, use the “Potentially Dangerous” flag and “Caution” bullets if appropriate. Make note of any steps that present a possible hazard—or that could become hazardous if performed inattentively or incorrectly—and warn your readers accordingly.
To add the “Potentially Dangerous” flag to the Introduction:
- Click the Edit button at the top of your guide.
- On the Introduction tab, scroll to the bottom and click on the Flags section.
- Select the “Potentially Dangerous” flag, and click Save.
- Write a few sentences in the introduction explaining the nature of the danger, so that readers know what to expect. Include any applicable safety tips and/or links to detailed safety guides.
- Save your work when you are finished.
To add the “Caution” bullet to any specific steps that could pose a safety hazard:
- When editing the step, click the black bullet next to your text in order to display the list of special bullets.
- Select the “Caution” bullet.
- In the accompanying text, clearly explain the nature of the hazard. Include detailed steps the reader should take in order to complete the task safely.
- Save your work when you are finished.
Some repairs require soldering, which may be intimidating for first-time fixers. Soldering can be both safe and fun, provided a few basic safety guidelines are followed.
Protect your lungs. Solder fumes can be toxic. At the very least they will irritate your lungs if inhaled, and may aggravate certain medical conditions such as asthma.
- Work in a well-ventilated area.
- Keep your head to the side of your work, rather than directly above.
Protect your skin.
- Use lead-free solder.
- Hold wires and solder with tweezers, or wear heavy gloves. Don't use your bare hands.
- Don't touch the tip of the iron. (If it's hot enough to melt solder, it's more than hot enough to burn you.)
- Wash your hands after finishing your work.
Protect your eyes. Solder can “pop” and “spit” unexpectedly, so wear safety glasses at all times.
Protect against heat, fire, and other hazards.
- Solder only on heat-resistant surfaces and materials. (Good: A piece of drywall. Bad: A ream of paper.)
- Keep your workspace tidy, and clear it of any flammable objects before you begin.
- Set the soldering iron down only on the iron stand.
- Never leave a hot soldering iron unattended.
- Keep a fire extinguisher nearby, and make sure you know how to use it.
- Don't eat or drink while soldering.
Protect the environment. Don’t throw lead solder, nor sponges contaminated with lead solder, into the trash. Put them in a sealed container and take them to your local household hazardous waste disposal facility. If circuit boards or other electronic components are beyond repair, recycle them responsibly.
CRT (Cathode Ray Tube) Displays
Do not attempt to disassemble or repair older, CRT televisions or computer monitors. CRT displays contain potentially lethal high-voltage capacitors, glass-walled vacuum tubes that can implode violently if mishandled, and large quantities of lead.
- You can recognize CRT displays primarily by their bulk: unlike modern flat screen LCD or plasma displays, which tend to be quite thin, CRTs are typically about as thick as they are wide.
- Choose only devices with non-CRT displays for your student project. Leave CRT display repairs to an experienced technician.
Flat-Panel TVs and Computer Monitors
Modern flat screen displays are much safer to service than older, CRT-type TVs and monitors. However, there are a few potential hazards to be aware of if you've chosen one of these displays for your project.
Unplug the TV from the power outlet before you begin work. This should go without saying for all electronic devices, but flatscreen displays contain power supply boards with large capacitors that can be particularly dangerous when charged.
Before touching any other internal components, disconnect the power supply from the main board.
- The power supply usually looks like a circuit board with a series of cylindrical capacitors that look roughly like battery cells.
- Avoid touching or prying near the capacitor leads unless you have verified that they are fully discharged.
Use extra caution with CCFL-backlit displays. Some pre-2010 flat screen displays used cold cathode fluorescent lamps (CCFLs) containing mercury. CCFLs look like long, tube-shaped fluorescent lights, usually placed behind or to the sides of the display. If broken, they may leak small amounts of mercury, which is very toxic. If you accidentally break a CCFL bulb:
- Do not touch any glass shards or spilled liquids with your bare hands.
- Wear protective gloves, and clean the area with a damp rag.
- Keep the area well-ventilated.
- When finished, wash your hands thoroughly.
- Be sure to put any mercury-contaminated shards or rags in a sealed container and dispose of them responsibly.
Microwaves are among the most hazardous appliances to repair. They contain large, high-voltage capacitors capable of delivering a fatal electrical shock, and can also leak harmful levels of radiation if damaged or reassembled improperly.
- If you're unsure about what you're doing, get expert help or choose a different device for your student project.
- Do not touch any internal components or wiring until you have verified that all high-voltage capacitors are discharged.
- Never operate a microwave that looks damaged or imperfectly repaired. Be especially wary of damage to the door, hinges, latches, or seals.
Cars and Trucks
Fixing motor vehicles like cars and trucks can be very rewarding, but also comes with more hazards than a typical smartphone or laptop repair. If you choose to work on a motor vehicle project, take appropriate precautions.
Never work under a vehicle that is supported only by a jack. The purpose of the jack is to lift the car off the ground, not to hold it in place! An untimely jack failure can easily kill you. Secure your vehicle with jack stands, or use ramps to raise and lower it safely.
Choose secure jacking points. These vary from one vehicle to the next, so proceed with caution—a jack or jack stand placed under an oil pan or a power steering line won't protect you, and will likely damage your vehicle as well. If in doubt, consult your vehicle's service manual, or get help from an expert.
Park the vehicle on firm, level ground before raising it. Jacks, jack stands, and ramps are designed to be used on hard, level surfaces like concrete and asphalt. Never attempt to raise a vehicle that's parked on a slope or an unstable surface like grass, dirt, or gravel.
Secure the wheels and drivetrain. Raising cars and trucks can cause them to roll unexpectedly, even on a level surface. Before jacking up any vehicle, shift into Park (or first gear, if you have a manual transmission). Make sure the engine is off, and set the parking brake. Then, block the wheels opposite the jack with wheel chocks, bricks, or large wooden wedges.
Always disconnect the battery before beginning repairs. Battery type and location varies by vehicle, so consult your vehicle's user manual for exact instructions.
- There is a risk of electric shock if the battery terminals are handled incorrectly or inattentively. Observe the safety guidelines in your user manual, and get help if you aren’t sure what to do.
- Never work on a vehicle with the motor running. Even at idling speed, engine belts and fans can cause serious injury. Cooling fins rotate fast enough that they can be practically invisible at the edges, and can easily catch you off guard. There may also be electrical hazards at the alternator, spark plug wires, and other areas. If you need to start the engine, stay well clear of the engine bay, and make sure all four wheels are firmly on the ground.
Protect your eyes and skin. A pinched finger or a stray splash of brake fluid can leave you seriously, even permanently, injured (and bring your project to a halt, to boot). Wear heavy-duty gloves and eye protection at all times.
Protect your lungs. Cars and trucks contain an abundance of toxic substances, from brake dust to gasoline fumes. Work in a well-ventilated area, and wear a mask or respirator if appropriate.
Protect your pets. Don't leave automotive fluids—particularly coolant or antifreeze—lying around for your pets to find. Antifreeze commonly contains ethylene glycol, a toxic compound which nevertheless gives off a sweet odor that is appealing to many animals. Keep your coolant or antifreeze containers sealed, and transfer used fluids to a sealed container immediately after draining them from your vehicle.
Use the right tools. Taking shortcuts by trying to “make do” with a less-than-perfect tool can turn even a simple repair into one fraught with hazards, for both you and your vehicle. If you don't have the right tools, get them—or choose a different device to work on. Many auto parts stores have free tool checkout programs that can help you complete a repair properly, inexpensively, and safely.
Observe local laws, and protect the environment. Used automotive fluids such as motor oil, gear oil, transmission fluid, brake fluid, power steering fluid, and coolant (antifreeze) must be disposed of responsibly—along with any rags, paper towels, or filters that have been contaminated by these substances. Take them to your local household hazardous waste disposal facility in a sealed container. Never pour used automotive fluids down the drain or into the street.
Mobile Devices (Laptops, Tablets, & Smartphones)
Lithium-ion batteries power nearly all modern mobile devices. While they are not normally dangerous, they do store a large amount of energy—energy which can cause serious injury if released suddenly.
Never puncture a battery. Don't pry at batteries with screwdrivers or other sharp tools. A ruptured battery can rapidly heat up, catch fire, and even violently explode.
Don't bend or deform batteries excessively. It's normal for glued-in batteries, like iPhone and iPad batteries, to deform slightly when removed. However, excessive bending could rupture a cell and cause a fire. Use caution and try to keep any deformation to a minimum.
If you notice any battery smoking or swelling to large size, stop working and back away.
Digital camera flashes are powered by capacitors capable of delivering severe electric shock.
Don't be fooled! They may look innocent, but even small cameras contain capacitors that pack a wallop.
- The capacitor stores a charge drawn from the camera's battery. Be sure to remove the battery before you open the camera or attempt to discharge the capacitor.
- After opening a camera, avoid touching any internal components until you have verified that the capacitor is safely discharged.
Before disassembling or servicing any air compressor:
- Unplug the power cord.
- Open the bleed valve on the main tank to release any compressed air. Never work on an air compressor while components are under pressure.
- Never attempt to puncture air tanks with sharp objects or tools.
Proper lubrication is crucial to air compressor functionality and safety. When working on air compressors:
- Do not over lubricate.
- Use the correct oil or lubricant for your model. Avoid low flash point lubricants, which have the potential to ignite during operation and cause a fire or explosion.
PC Power Supplies
A typical PC power supply contains capacitors large enough to deliver a significant electrical shock.
- Never work on a power supply that is plugged in.
- After unplugging the power cord, press and hold the PC's power button for about 5 seconds. In some cases this will help drain capacitors that might otherwise have retained a charge.
- After unplugging the power, wait 10 minutes before disassembling the power supply. Capacitors used in PC power supplies typically lose any remaining charge a short time after being unplugged.
- Nevertheless, assume all large capacitors are charged unless you have confirmed otherwise. Safely ground or discharge all large capacitors before handling internal power supply components.