Soldering and welding flux contains chemicals which are irritating to the eyes and respiratory system, prompting many industrial countries to put occupational hazard standards in place to control fumes in the workplace. Some kinds of soldering flux may also contain high levels of toxic lead. Likewise, smoke of any kind contains particulates that can have severe negative consequences to one’s health in the long run, and welding smoke can cause damage to delicate electronics. Other processes that can release noxious fumes and smokes include laser etching and plasma cutting.

Where possible, such fumes should always be extracted at their point of origin. The type of fume will determine which extraction method should be used. Electrostatic discharge (ESD) safe units are best when working with sensitive electronics.

Extraction systems generally have a vacuum pump with a correctly sized motor, a hood, small tube, or nozzle over the working area, and a filter device.

Tip extraction with a tube works best when soldering is being done by hand. A tube is clipped to the soldering iron or forms part of it, extracting the fumes within millimetres from the source.

With heated air repairs, solvents, solder pots or adhesives, arm extraction is often used. A hood or funnel attached to an adjustable arm is put near the operation being done.

Filtering systems for local extraction may contain a dust filter, micro filter and a gas filter. The dust and micro filters remove larger and smaller particulates respectively and help to extend the life of the gas filter. The micro filter is typically a HEPA filter with more than 99% efficiency. The gas filter contains activated carbon impregnated with chemicals to remove gaseous pollutants, and is structured to maximise contact between the filter media and gases entering the filter.

Filters may last three to twelve months. The precise lifetime depends on the type of contaminant and the contaminant load handled. Some systems can include an indicator for when the filter should be replaced.

The vacuum pumps that are used differ. Tip extractors require pumps that produce strong vacuums so that high airflow velocities can be achieved in the narrow tubes. Arm extractors need pumps that can handle higher volumes and produce lower negative pressures.

Local exhaust ventilation (LEV) is intended to control airborne contaminants by capturing them as near to their source as possible. This type of system tends to be much more effective at preventing dangerous fumes and other pollutants with a specific origin from being breathed in by workers than general exhaust systems. Pollutants may include smoke, dust, fumes, oil mist, solvents and other volatile organic compounds (VOCs), and steam.

LEV systems are preferred where air contaminants are especially hazardous to health, where the dust and fume loads are heavy, where emission occurs from a small number of sources (especially if the sources are close to workers’ breathing zones), and if temperature control costs may increase when general ventilation is used.

Pressurised hoods may be used, or an area may be pressurized and exhausted with fans.

Systems for local exhaust ventilation generally use several elements:

• A hood, arm or other device to trap the contaminant near the source.
• Air ducting.
• An air mover (i.e. fan).
• A device such as a filter to remove the pollutant.
• A stack for exhausting the air.

In addition, ventilation is needed to provide make-up air, but this can often be accomplished by means of general ventilation.

For fume extraction hoods, it is important to note that face velocity does not adequately reflect hood extraction efficiency, although it is a contributing factor. With bypass hoods, face velocity often changes when the inlet baffle is adjusted, while evacuatory volume is nearly constant.

In addition, face velocity measurements are sometimes inaccurate or inadequately confirmed. To determine hood face velocity, multiple readings should be taken as velocity can change dramatically across time.

CFW offers the Eezivent portable ventilation system, optionally equipped with flexible ducting, for point extraction of fumes and smoke.