In most cases, this is a normal phenomenon. However, that is not always the case, and the key lies in distinguishing between smoke caused by the protective layer burning off once and smoke signalling a device fault.
Why does smoke appear during the first power-on?
It almost always comes from the protective oil layer on the soldering tip or heating element, applied by the manufacturer before packaging to prevent rust during transport and storage. When the tip or heating element reaches operating temperature for the first time, this oil layer burns off within a few dozen seconds to a few minutes, producing thin light grey smoke and a mild burning smell, similar to the smell when turning on a brand-new oven or electric stove. This is a one-time occurrence that only happens during the first few power-ons, then disappears completely.
The simplest way to handle this: let the soldering station run idle at normal working temperature (around 300 - 350°C) for 5 - 10 minutes in a well-ventilated area before starting to solder, similar to "burning off" a newly purchased oven. There is no need to turn off the machine midway; just let the oil layer burn off naturally.
Smoke accompanied by a burning plastic smell or a harsh pungent odor
This is where you need to clearly distinguish from the above case. If the burning smell does not fade after a few minutes but becomes increasingly harsh, with a strong smell of burning plastic or metallic burning, accompanied by thicker smoke than usual, you should unplug the power immediately and inspect the device.
Several common causes in this group: the power cord or handpiece cable was pinched during packaging, the plastic handle casing is too close to the heating zone, or the control circuit board inside the soldering station has a component defect straight from production. This case is rare, but it does happen, especially with cheap soldering stations of unknown origin.
Quick way to distinguish: smoke from protective oil usually fades and disappears completely in a single power-on. Smoke from a equipment fault usually does not decrease, and may even be accompanied by unusual noises from the circuit board, an increasingly strong burning smell, or the handle casing becoming abnormally hot instead of just the soldering tip.
Read more: Quick Fix for Solder Not Melting? How to Handle It
Why is there a burning smell even after using it a few times?
If the soldering station has passed its first power-on, the smoke has stopped, but a smell returns later, the cause is usually no longer the protective oil layer, but shifts toward the user side.
A mild burning smell during each soldering session usually comes from rosin in the solder core or flux burning when touched by the soldering tip; this is a normal smell of the soldering process and not a device fault. However, if the smell is noticeably stronger with thick smoke, it may be due to dust buildup on the handpiece or the connection cable being exposed to heat over time; clean the machine body and check if the cable sheath is cracked or coming into contact with the heating zone.
Refer to Soldering Stations at EMIN: https://emin.vn/cong-cu-thao-lap-may-han-thao-lap-lam-mach-dien-tu-smt-tram-han-thiec-441/pc.html
Are soldering and lead fumes harmful to health?
Yes. Whether it is smoke from burning protective oil on the first run or fumes generated when soldering lead-solder, the composition contains ultrafine metal dust and rosin fumes from the flux. Inhaling this over a long period can affect the respiratory tract. For regular soldering work at a workbench or maintenance shop, work in a well-ventilated area, avoid leaning your face directly over the fume area, and consider using a small fume extractor placed next to the soldering position if you solder frequently throughout the day.
