When the solder is lead (lead is not excreted by the body and is harmful), then an exhaust hood is needed.
If you solder with rosin, gel rosin, LTI-120 (soldering flux LTI 120 consists of 25% rosin and 75% alcohol solution with active ingredients) and lead-free solder (SnCu, Sn97Cu3, E Sn100 C, others,) is it still needed?
One could argue that the exhaust is even more important in the case of lead-free solder than in the case of leaded solder. The flux used with lead-free solder tends to be worse for you than that used with leaded solder, and the fumes are 100% flux--even when using leaded solder, there is no lead in the fumes.
The possibility of lead poisoning comes primarily from lead residue on the operator's hands, not from inhalation. If not washed off, the lead can get into food or rubbed into eyes. Note also that metallic lead, as found in solder, is not as toxic as lead compounds as found in lead paint or leaded gasoline, and most of it will pass right through your body--though it's still not harmless, so do be sure to wash it off. The reason lead solder is banned in many applications is less due to risk to the operators and more due to environmental hazards; lead that ends up in landfills or otherwise discarded will naturally convert over time to more toxic forms.
We had this topic discussed here many times. It has nothing to do with lead what-so-ever since the temperature of a solder iron is nowhere near hot enough to vaporize any of the metals involved - in which case you would be melting the components as well. Soldering is not welding.
Whenever you do any form of professional soldering, you always need a solder fume extractor, which are devices that come in various shapes and sizes. Often it is a hose of some kind which you fix near the solder area, which vacuums out the harmful gasses away from your face and into some manner of filter.
Just using some DIY fan is not recommended. Holding your breath is not recommended.
The sole purpose of this is to extract vaporized flux and other chemicals from the solder core. These gasses are harmful and can cause various allergies and respiratory problems. RoHS solder is more unhealthy since it melts at approximately 30°C higher temperature than leaded solder, which in turn means more vaporized flux. RoHS was sadly never meant to protect the PCBA assembly operator from chemicals.
Additionally, touching the plastic parts of some connector by accident with your tip happens now and then, even to veterans. There's no healthy gasses coming out of that either.
It is particularly unhealthy to do repair work on PCBA which were covered in conformal coating, glue, silicone or similar. Then a fume extractor is not enough, you need to do such work inside a chemistry hood. Remove as much of the chemicals as possible with isopropyl, then use plenty of external flux. And don't use your finest solder tip...
Soldering is an industrial process, so you need to wash your hands after soldering. Lead is only harmful if you manage to get it in your mouth. And for this reason you shouldn't do soldering in the living areas of your home, getting solder splatter on the floor where small children or pets might be exposed to it.
Probably not, Lead has a boiling point of 1750C and not much if any vaporizes at 230C (typical soldering temp). That being said it isn't zero. But you probably get more by eating fish than through the air. (I couldn't find any resources on how much lead get's vaporized, but with the amounts and similar studies I've done on broken CFL's and mercury you get more by eating fish with mercury, which is about the same molecular weight. Salmon can give you 10-160ug of lead in one fish dinner. I'm willing to be that if you are heating lead, you'll get less than 10ug by breathing.)
But that isn't why you need a fume extractor (usually fume hoods are not used, extractors with an activated carbon filter are enough)
The reason why you have a filter is for halides which are halogens like chlorine, bromine, iodine, or fluorine that are found in fluxes. These are way worse for you to breathe in but not as toxic as lead.
So use a fume extractor (or hood)
