Section 540 - EMISSION OF AIR CONTAMINANT: CONCEALMENT AND MASKING540.1 It shall be unlawful for any person to willfully cause or permit the installation or use of any device or use of any means which, without resulting in a reduction in the total amount of air contaminant emitted, conceals an emission of air contaminant which would otherwise violate the emission standards of this Regulation.540.2 It shall be unlawful for any person to cause or permit the installation or use of any device or use of any means designed to mask the emission of an air contaminant which causes detriment to health, safety, or welfare of any person. Wash. Admin. Code Northwest Clean Air Agency, 500, 540