Why should I use a fume extractor instead of an ambient (overhead) air cleaner?

Ambient air cleaners are effective supplements to fume extractors, but should be avoided as a primary tool for fume control. Because of the nature of how ambient air cleaners work, fumes must first pass by a welder’s breathing zone before drifting into the capture zone of the ambient unit. As such, the welder is exposed to as much dangerous welding fumes as if he or she had no extraction equipment at all. As stated, it is best to use ambient air cleaners to support source capture fume extractors and to provide general air cleaning and circulation.