Why should I use a fume extractor instead of placing fans in my shop to blow the fumes away from my welders?

The practice of using fans and blowers in this manner is called the dilution method, and while it is commonly used, this method may not be effective in removing weld fumes in any except the smallest of shops. Disadvantages include lack of uniformity in diluting the fumes throughout the shop, downstream concentration of fumes as they are blown away from the fan, temperature variations throughout the shop, inability to actually decease overall exposure levels of hazardous welding particulate, among others.