# 61.181 Definitions.
All terms used in this subpart shall have the meanings given them in the Act, in subpart A of part 61, and in this section as follows:
*Arsenic kitchen* means a baffled brick chamber where inorganic arsenic vapors are cooled, condensed, and removed in a solid form.
*Control device* means the air pollution control equipment used to collect particulate matter emissions.
*Curtail* means to cease operations to the extent technically feasible to reduce emissions.
*Inorganic arsenic* means the oxides and other noncarbon compounds of the element arsenic included in particulate matter, vapors, and aerosols.
*Malfunction* means any sudden failure of air pollution control equipment or process equipment or of a process to operate in a normal or usual manner so that emissions of inorganic arsenic are increased.
*Opacity* means the degree to which emissions reduce the transmission of light.
*Primary emission control system* means the hoods, enclosures, ducts, and control devices used to capture, convey, and remove particulate matter from exhaust gases which are captured directly at the source of generation.
*Process emissions* means inorganic arsenic emissions that are captured and collected in a primary emission control system.
*Roasting* means the use of a furnace to heat arsenic plant feed material for the purpose of eliminating a significant portion of the volatile materials contained in the feed.
*Secondary emissions* means inorganic arsenic emissions that escape capture by a primary emission control system.
*Shutdown* means the cessation of operation of a stationary source for any purpose.
[51 FR 28033, Aug. 4, 1986; 51 FR 35355, Oct. 3, 1986]