a process device which is used to control the process
This is any type of equipment that reduces the concentration of a pollutant in an exhaust gas. The control device is referred to as “add-on†technology as opposed to “pollution prevention,†which is designed to control pollution by altering the underlying manufacturing process. A control device may destroy a pollutant or capture it for subsequent recovery. Examples are incinerators, carbon absorbers, and condensers.
Any device that senses, switches, or regulates an operation (e.g., switch, valve, brake).