(a) Natural gas-fired boilers and process heaters sold, distributed, installed, or offered for sale within the State of Texas must meet the following specifications for nitrogen oxides (NOX ). (1) Type 0 units manufactured on or after July 1, 2002, but no later than December 31, 2004, must not exceed: (A) 40 nanograms per joule (ng/J) of heat output; or (B) 55 parts per million by volume (ppmv) at 3.0% oxygen (O2), dry. (2) Type 0 units manufactured on or after January 1, 2005, must not exceed: (A) 10 ng/J of heat output; or (B) 15 ppmv at 3.0% O2, dry. (3) Type 1 units manufactured on or after July 1, 2002, must not exceed: (A) 40 ng/J of heat output; or (B) 55 ppmv at 3.0% O2, dry. (4) Type 2 units manufactured on or after July 1, 2002, must not exceed: (A) 30 ppmv at 3.0% O2, dry; or (B) 0.037 pounds per million British thermal units (lb/MMBtu) of heat input. (b) Natural gas-fired water heaters sold, distributed, installed, or offered for sale within the State of Texas must meet the following specifications for NOX . (1) Type 0 units manufactured on or after July 1, 2002, must not exceed: (A) 40 ng/J of heat output; or (B) 55 ppmv at 3.0% O2, dry. (2) Type 1 units manufactured on or after July 1, 2002, must not exceed: (A) 40 ng/J of heat output; or (B) 55 ppmv at 3.0% O2, dry. (3) Type 2 units manufactured on or after July 1, 2002, must not exceed: (A) 30 ppmv at 3.0% O2, dry; or (B) 0.037 lb/MMBtu of heat input.