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I do a fair bit of soldering (lead-free). Is breathing in solder/flux/paste fumes actually going to harm me?

Are cheap fume extractors worth buying?

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    \$\begingroup\$ Solder fumes are pretty much entirely vaporized flux. Different people react differently to the fumes. This ranges from absolutely no discernible effect at all over decades of daily exposure to triggering an asthma attack the first time someone is exposed to the fumes. Oldsters: keep doing what you've been doing for decades. Newbies: buy an inexpensive fan-type extractor with attached filter - and USE it. \$\endgroup\$
    – Dwayne Reid
    Commented Mar 26, 2015 at 23:35
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    \$\begingroup\$ Note that traditional rosin flux is also called "colophony incense," also "kolophonium." It's meant to be inhaled ...but read up on incense allergies, also on "sensitizing" during repeated exposure. ("Rosin" is just pine-sap with the volatiles or "turpentine" boiled out.) \$\endgroup\$
    – wbeaty
    Commented Sep 11, 2018 at 19:10

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Solder fumes aren't very good for you. Some people can become sensitized to flux fumes, especially from the older rosin flux used in cored solder, and get breathing problems:

Controlling health risks from rosin (colophony) based solder fluxes

The no-clean flux isn't as bad.

I once felt quite ill after assembling about 30 boards that I had to do myself as my distributor wanted them very quickly.

Breathing out whilst you are soldering each joint helps a lot, if you don't have fume extraction.

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  • \$\begingroup\$ 'The no-clean flux isn't as bad.' - really? The products containing no-clean flux are usually sold with a 'Harmful if inhaled', 'May cause allergy or asthma symptoms or breathing difficulties if inhaled', 'May cause respiratory irritation' warnings (besides others) ... (example) \$\endgroup\$
    – maxschlepzig
    Commented Jul 18, 2022 at 10:26
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My first reaction to your question was, yes the fumes are going to harm you. My second was to conduct some quick research.

Amazingly, as I quote next, Lead-Free Solder inhalation can lead to pneumonia and a 24-48h flu.

INHALATION: Inhalation of dusts and fumes may cause irritation of the upper respiratory tract. Inhalation of freshly formed metal oxides may cause metal fume fever, a brief (24-48 H) flu-like illness. Inhalation of tin oxide may cause pneumonia.

According to the MSDS from Weller on some of their non-lead solder.

You can guarantee this must be a frequent event or the company would not be disclosing this in such a cavalier manner.

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    \$\begingroup\$ Non-lead and lead-free solder is same thing? \$\endgroup\$
    – Boris_yo
    Commented Sep 19, 2011 at 18:30
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    \$\begingroup\$ @Boris_yo I think yes, this is same thing. This is metal alloy not containing lead (Pb). All this mess with lead or non-lead solders comes from EU, where we can't use lead because its toxic, but we can put pure lead into river or lake while fishing :D \$\endgroup\$
    – Kamil
    Commented Jun 29, 2014 at 9:47
  • \$\begingroup\$ So lead is toxic but pure lead is not? What toxin does non-pure lead contain that makes it toxic? \$\endgroup\$
    – Boris_yo
    Commented Jun 30, 2014 at 6:19
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    \$\begingroup\$ @Boris_yo Lead is toxic, pure or otherwise. Kamil is complaining about the inconsistency of the laws, not saying that one situation is healthier than the other. \$\endgroup\$
    – endolith
    Commented Jul 17, 2017 at 13:35
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    \$\begingroup\$ One problem is that the soldering is heated up, the fishing gear isn't. \$\endgroup\$
    – Anders
    Commented May 14, 2019 at 12:52
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Breathing the fumes is not good for you. With the additional flux required to get good SMD solder joints there are more fumes.

I just bought a Weller WSA350 smoke absorber. It was $50 new. A three pack of filters is pn WSA350F. This works OK. A unit with a stronger fan would be better. After a few hours of soldering there is a fair amount of white powder on the carbon filter. The fan looks like a standard 5" boxed fan so I may try getting a more powerful one.

When the weather is good I have cross ventilation so I put an exhaust fan in the window near my bench.

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Fume extractors are worth every penny in my opinion. Smoke goes in - no smoke comes out - and the best bit is that the air smells clean.

If you're in the UK, get the cheap Maplins one for £15.

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    \$\begingroup\$ The cheap ones seem not to work that well, though: ncbi.nlm.nih.gov/pubmed/9838864 \$\endgroup\$
    – Miguel
    Commented Dec 25, 2016 at 12:34
  • \$\begingroup\$ Maplin, that brings back memories. RIP \$\endgroup\$
    – Mark K Cowan
    Commented Apr 19 at 21:42
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All solder fumes can cause occupational asthma and other health problems (leaded and lead-free) if used for long periods at a time.

The best solder wire contains something called Rosin that helps the solder flow when hot. This causes asthma if you are over exposed and is irreversible. Other solder wires that are Rosin free cause other health problems and are rubbish to solder with.

Invest in a good extractor, not a cheap one. Trust me, it's not worth the risk and I'm talking from experience. I have occupational asthma from solder fumes containing Rosin (colophony) after my job as an RF Development technician. I was employed in that position for 18 months only and am now registered disabled with lung damage after being challenge tested at the Royal Brompton Hospital in London.

This thread is old but I thought i'd post it in case anybody new reads it.

Download the safety data sheet from the internet for the solder wire you are using and read the hazards before using it.

I had no previous lung problems before that job, I was physically fit, 6' 5" tall, 17 stones and I was 38 years old at that time. I had no idea how damaging those fumes could be. Like cigarettes, the fumes can also be invisible to the naked eye, but are more damaging. If you are doing a lot of soldering make sure you take a lot of breaks and get some fresh air inside you as well as having a decent extractor that sucks well. Position the extractor hose directly above the area you are soldering and make sure it is working properly before going anywhere near the area being soldered. You should be okay if you do that. If you don't have an extractor then stick to about 10 minutes of soldering a day and then get plenty of fresh air inside you afterwards and you should be okay. Hope this helps.

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    \$\begingroup\$ good feedback. i run a repair shop and i'd say i do soldering at most 10 minutes max in a day. its in a small room with low ceilings. im curious to what happens to the fumes over time? as my place isn't very well ventilated. wouldn't want to have a toxic contaminated room. \$\endgroup\$
    – Patoshi パトシ
    Commented Mar 28, 2015 at 17:35
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You could always try building one. I've been meaning to one of these days, but I haven't done a whole lot of soldering recently. Googling turns up a bunch of people that have done this before in different ways.

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  • \$\begingroup\$ Sadly only one of those links still works. Seems like link rot on the web is getting faster as time goes by. \$\endgroup\$
    – Noah
    Commented Aug 18, 2018 at 16:27
  • \$\begingroup\$ Updated dead links with some new google results. Let's see how long these ones last! \$\endgroup\$
    – davr
    Commented Sep 11, 2018 at 18:14
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Yes, but it all about exposure time.

If you solder 8h per day and 5 days per week your exposure is quite high and the odds of side effect if you don't ventilate it away is quite high.

On the other hand, if you solder a couple of prototype boards now and then, and you don't directly inhale the fumes the amount of chemicals is probably not that high.

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I've been soldering daily for 35-odd years and the only time I do anything about fumes is if I'm doing a production batch, when I stick a 4" fan at the side of the bench to blow air across, which is as effective as extraction, and doesn't get in the way. Unless you are allergic or find it annoying I wouldn't worry too much unless you're doing it continuously all day. I do find the flux in LF solder significantly more irritating, which is another reason I rarely use it.

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  • \$\begingroup\$ And besides... hardly anyone notices that extra finger growing out of your forehead.. (LOL Sorry I could not resist.) (Also 35+ years and counting--->) \$\endgroup\$
    – Trevor_G
    Commented Mar 7, 2017 at 16:56
  • \$\begingroup\$ "Unless you are allergic or find it annoying I wouldn't worry too much" Never to late to get a new allergy! Use fume extractors. Almost everyone I know who have worked with professional PCB assembly most of their life have gathered their fair share of allergies or lung problems. You don't get those from "bad luck", you get them from toxic chemicals. \$\endgroup\$
    – Lundin
    Commented Mar 13, 2023 at 7:39
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I work very closely with my pieces. I worked on electronic boards years ago and did not find I had a problem but I also worked in a professional environment that filtered the room. When I first started working with solder at home I thought that I was just going to be working a few times here and there (Stained Glass Hobby). I quickly found after 3 hours of soldering that I had a head ache and the next morning my sinuses were bothering me. I also found that my eyes were gunked up. Thinking this is just pollen I returned the following day to my beloved project and soldered for 4 hours. I did this for 3 consecutive days until I realized that it was more damaging than I thought.
Now I have to wait for my sinus membrane to recover before I can get back to my project (which takes more solder than the average computer board). I have also found that my joints hurt. I don't know if this is part of the exposure or just age. I have now ordered one fume extractor for up close and will be looking into another. If you are working with solder, and it is sporadic, I suggest you have a small one. If you work with solder regularly, I suggest a strong one. I am now researching different ones to see which would be appropriate for my usage.

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Solder fumes can have halides in them. The flux containes halides which means bromine and chlorine for most fluxes. These ions are not good to breathe in. With most fluxes you can check the content of the flux in it's corresponding datasheet if it's available.

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