base(Any chemical species, ionic or molecular, capable of accepting or receiving a proton (hydrogen ion) from another substance; the other substance acts as an acid in giving of the proton; the other ion is a base; chemical)
permissible exposure limit(An exposure limit that is set for exposure to an hazardous substance or harmful agent and enforced by OSHA (Occupational Safety and Health Act) as a legal standard. It is based on time-weighted average concentrations for a normal 8-hour work day and 40 hour work week)