# Solder Fumes - Activated Charcoal vs Outside Venting

Like probably everyone else here I do a ton of soldering. When I setup my current workshop I built a fume extractor that actually goes in a window near my bench. Basically just a length of dryer duct with a high flow fan that vents directly outside. This is all an well, but kind of annoying to setup every time. I did this because, at the time, I felt that venting directly outside was clearly going to be better than an activated charcoal filter.

So, was I wrong? Can a simple filter be just as good as exterior venting? Or at least close enough? Has anyone ever found any hard data on how much lead and other toxins a charcoal filter will remove? Would adding a HEPA filter in the mix help?

• According to Weller "Solder fumes consist of 99.5% particles and 0.5% gases. Particles in solder fume that are a threat to human health are lead particles (in dust and smoke) larger than 0.1 micron and fumes of aliphatic aldehydes and isocyanates." - so a HEPA filter might help. – RedGrittyBrick Jun 24 '14 at 13:36
• The boiling point of lead is over 1700C. The flux fumes are all I have ever worried about. You will get some lead on your fingers though. – Matt Jun 24 '14 at 14:21
• I have never used a fume extractor or filter in over 40 years of R&D soldering. I just breathed out when soldering to blow the fumes away before breathing in. However, some people are allergic, or can build an allergy to the flux. Plus, if it's not just you in the room second hand smoke may be a problem. – Dirk Bruere Apr 27 '18 at 9:37
• The flux fumes have always bothered me, causing congestion, so a bit of a breeze helps, but for the amount of hand soldering I do it's not a big deal. – Spehro Pefhany Apr 27 '18 at 13:32

A simple filter isn't as good as outside venting, no. A good quality, well designed filter is though. The problem is that such filters tend to cost rather a lot compared to basic charcoal mesh + fan arrangements.

I'm soldering since I was 12 (31 now). At work we have all kind of high quality (regulated) equipment including solder fume extractors with the filters and everything. The lab that we use in R&D is not well ventilated (no windows) so we use the fume extractors. These things work, however you do have to change the filters every few months and at work I don't care as they pay for it but at home I would not like the additional overhead and have a feeling I would forgot to buy new filters and stop using it as some point.

The biggest problem with these extractors is that they make annoying noise and you always hear it because the device is pretty close to your workspace. At home I've setup a system which is similar to your's I think. I took a white duct about 2M long and on the far side I've installed two 12V PC fans that suck the air to the outside (secured them with hot melt glue). I ran them with PWM so both of them spin slowly and don't make too much noise. The end of the duct which sits with the fans on the window has a mesh on it to prevent things from crawling into the duct like bugs, I sometimes leave it out for half a day... The other side of the duct is above my bench and it works like a charm. The noise is very low as the fans are both relatively far and spin slowly and I don't need to maintain the system other than opening the window.

Here is a picture of a similar device to what we have at work:

Looking around the usual buying sites, I found that a bench fume extractor can be had for $30-$50. Activated charcoal filters are about $5 for a 4-pack. Here is a quick guide to the kinds of fumes you can expect when soldering. Most of the gasses released are particulates. Flux releases resin acid particulates and gasses when heated above 360 F, which is well within the range of normal soldering. This accounts for 99% of the smoke. The biggest risk is due to the inhalation of particulates, which can produce symptoms similar to asthma. Plus those particulates on your face can irritate skin and eyes. So it is worth using fume extraction, if only to save your lungs. HEPA is much more expensive. Removal to outside is a good alternative, but, as you pointed out, is itself a job to set up each time unless you have it built into your workbench. So my answer is to simply pick up one of the inexpensive desktop fume extractors and buy some spare activated charcoal filters. Thanks for your question. I am going to buy one now, myself. Less than$30, and a 10-pack of filters for under \$7. At least it will keep this stuff out of my eyes.

• Thank you for the edit, Mr. Lee. I didn't know how to do that. – SDsolar Nov 26 '16 at 15:47

I’ve heard that carbon filters are proven poor. The better choice is positive pressure or sucking air in from the opposite side of the room and have a fan like box fan pushing air out the window the workbench is next to.