Proper air flow for sewers and water tunnels is fundamental to supply acceptable airflow, containment of fumes, and dispersion of gases into the atmosphere. Fans are used to exhaust or provide air and are uncovered to a multitude of harsh chemicals, temperatures and slight abrasives. To fight these corrosive environments, there are a wide variety of options such as stainless metal construction, hot-dip galvanizing, and corrosion-resistant coatings. Fans are used in scrubber systems, odor control, thermal oxidation, and generic ventilation.