Soldering is a process of joining two metals by introducing a molten filler metal into the joint but without melting the host metal components. The most common applications are in electronics assembly and plumbing but there are many other applications. In the past lead was a major component of solder but increasingly low lead or zero lead alloy is used. Nevertheless workers must be protected from breathing in the sub-micron fumes generated during the soldering process, especially when the work is on an industrial scale. For an individual work station a free standing fume extractor unit is appropriate but where there are multiple work stations a multi branch fume extraction system is required. Because the fume is relatively small in quantity and has little velocity small diameter ducting and small articulated hoods are used. At a remote location a centralised filter will filter the fume. Because of the sub-micron nature of the fume and the likelihood of toxic components a high efficiency filter is needed such as OptiFlo RC.