Soldering involves handling metal at about 350°C, producing fumes, touching substances like lead, and sometimes working directly with electricity. A little care greatly reduces the danger, yet most accidents happen in a moment of carelessness thinking "it will only take a second". This article covers the common hazards in soldering (burns, fire, fumes, lead, eye injury, and electricity) and the work environment and rules that go with them. It is not medical advice, and if discomfort continues, consult a professional.
Hazards and measures at a glance
| Hazard | Cause | Key measure |
|---|---|---|
| Burns | Iron tip (about 300–400°C), freshly soldered spots | Use an iron stand; wait until it cools after work |
| Fire | Leaving the iron near flammables, leaving it on while away | Heat-resistant mat, a tidy bench, turn off when leaving |
| Fumes and gases | Flux (rosin) smoke | Ventilation and a fume extractor |
| Lead exposure | Handling leaded solder | Wash hands, do not eat at the bench |
| Eye injury | Solder splatter, cut leads flying off | Safety glasses |
| Electric shock | Working while power is connected | Work with power off, discharge large capacitors |
| Battery accidents | Shorting lithium batteries | Protection circuit, fuse |
Preventing burns
- Always rest the iron on its stand. If you lay it on the desk, it rolls or the cord catches and it falls.
- Route the iron's power cord so it does not pass near the tip, and so no one trips on it.
- Freshly soldered spots, cut leads, and the iron tip are all hot for a while. Do not touch them until they cool.
- When handing over an iron, always give the handle end.
Preventing fire
- Keep flammables such as paper, cloth, alcohol (IPA), and sprays away from the bench. IPA catches fire easily, so do not use it near the iron.
- Work on a heat-resistant mat or a metal tray.
- Turn the iron off when you leave your seat. The habit of switching off even for a quick trip to the bathroom is the most effective safety rule.
- For regulated iron stations, choose a product with a sleep function that turns off automatically after a set time (How to Choose a Soldering Iron).
- Keep a fire extinguisher or a wet towel nearby.
Ventilation and fumes
Most solder smoke is flux (rosin) being heated. Rosin smoke irritates the eyes, nose, and throat, and can trigger asthma symptoms in sensitive people.
- Work with a window open or a ventilation fan on. Let the airflow carry the smoke away from your face, not blow it toward you.
- Placing a fume extractor (with an activated carbon filter) close to your work position is the most effective. A distance of 10 to 20 cm from the tip is good.
- Do not lean your face over the smoke while working. To see parts close up, use a magnifier or microscope.
- If the smoke is heavy, there is too much flux or the temperature is too high, so reduce it.
- Do not work for long in places where ventilation is hard (a small room, a basement).
Handling lead (leaded solder)
The amount of lead that vaporizes at soldering temperature is very small, and the everyday risk is the path of lead on hands reaching the mouth.
- After touching leaded solder, wash your hands with soap before eating or drinking.
- Do not eat, drink, or smoke at the bench.
- Gather solder scraps, used solder wick, and wiping cloths out of reach of children and pets, and dispose of them following local guidance.
- If you are pregnant, there are children around, or ventilation is poor, using lead-free solder is also an option (Choosing Solder and Flux).
Eye protection
- When soldering, solder or flux can splatter into your eyes, and leads cut with side cutters can fly off.
- Wear safety glasses. Ordinary glasses block somewhat, but the sides are open.
- When cutting leads, hold the lead with one hand or point the cutting direction away from your body.
Electrical safety
- Do not touch a circuit with your hands while power is connected. Do work and fixes with power off.
- Beginners should not touch circuits connected to AC mains. Even if you use a power adapter, do not open it.
- A large electrolytic capacitor holds charge even after power is turned off. In high-voltage circuits, discharge through a discharge resistor before working (Capacitor Types and Polarity).
- Lithium-ion and lithium-polymer batteries can catch fire from a short or overcharging. Use products with a protection circuit and add a fuse.
- Before powering up for the first time, check for shorts with a continuity test (It Is Finished but It Does Not Work: A Step-by-Step Checklist).
Static electricity (ESD)
A human body can build up thousands of volts of static, and CMOS ICs (74HC, CD4000) are weak to it. Touch grounded metal before handling ICs, use anti-static bags and mats, and take extra care on dry winter days (Reading DIP IC Pin Numbers and Using IC Sockets).
Keeping the bench tidy
- Prepare bright lighting and a magnifier. In the dark you miss cold joints and bridges.
- The habit of returning parts and tools to their place after use reduces accidents.
- Match chair and desk height to reduce strain on your neck and back, and take a break once an hour.
- Work at times and places where children and pets do not come near.
After work
- Turn off the iron and leave it on the stand until it cools.
- Tidy up solder scraps and used wick.
- Wash your hands with soap.
- Wipe down the bench.
Summary
Safety in soldering starts with making five things habits: "use the stand, turn it off, ventilate, wear safety glasses, and wash your hands". The habit of turning off the power when you leave prevents the most fires. When you are ready to work safely, go back to Soldering Basics and continue practicing.