Ultra-compact single and two-stage Scott brand regulators are designed for working with reactive or corrosive gas mixtures. The SilcoNert 2000 passivated surface treatment makes surfaces one hundred times more inert than untreated 316L stainless steel. Adsorption of reactive or corrosive gases is virtually eliminated. The extremely compact design makes these regulators easier to handle and results in low internal volume as well. This shortens cycle and purge times allowing the user to work more efficiently while reducing consumption of costly specialty gas.