Out of the possible fume extraction methods, the most effective would definitely be source capture. This keeps the contaminant(s) out of the operator’s breathing zone, the area in which most negative effects can occur. Capturing the fumes at their source most often involves a source capture hood, such as a parabolic hood attached to a flexible arm that connects to the air cleaner, or a canopy hood localized directly over the process. Welding applications are more likely to call for a source capture arm with a hood attachment, whereas a machining process that gives off fumes and vapors is more likely to utilize a hovering canopy hood placed over the problem zone.
There are times when source capture is either not practical, or possible. In instances like these, ambient fume extraction is used to give the volume of space a number of air exchanges, based on the amount of contamination. I have encountered a number of applications in which using source capture simply wasn’t a feasible option. This one application in particular called for welding fume extractors, but the welders were constantly on the go, as it was simply touch-up work, so there was no time to reposition a source capture hood for anybody. The area in which their welders spent their shift was totally enclosed, so ambient collection was definitely possible… Unfortunately, the area was so large that to effectively circulate the air, it would take the airflow of a small monsoon, so that’s a dilemma in and of itself… There are definitely factors that come into play that will determine the ease or difficulty of solving a fume issue.
If a job is intermittent enough (for example, non-production), then portable fume extraction is usually preferred. This provides the welder(s) with a mobile solution that can be put away after use, conserving floorspace, and that puts a smile on some shop manager’s faces. That being said, some of the more effective fume extractors are roughly the size of a soda machine, but in some cases, you can’t make due with anything less. Larger production jobs that involve multiple workstations may benefit more from using a centrally located fume extraction system, with a network of ducting to provide each station with its own capture point. This is generally more economically efficient, from an equipment standpoint.
Now, on to filtration technologies…
There are certain applications that call for certain types of filtration/extraction; for instance, if you were working with lead fumes, an Industrial Hygienist may recommend that you use HEPA filtration due to exposure limits. It is very important that you choose the proper filtration technology to suit your needs; otherwise, chaos could ensue. A good bit of fume extraction can be handled with electrostatic filtration. This not only reduces recurring cost by providing washable, reuseable filters, but is often preferred for continuous welding applications due to filter loading capacity.
Another factor to take into consideration is odor. No, not welder’s body odor, but the olfactory properties of the welding oxides. True, by reducing the amount of oxide, you will reduce the amount of fume odor, but sometimes that isn’t quite enough. To effectively tackle this, you should consider using granulated gas phase media, more commonly known as activated carbon; as luck would have it, most industrial welding fume extractors can accommodate significant amounts of granulated carbon, and some modules are even bulk refillable, if you feel like getting your hands dirty.
