Combined sources of contaminant
 12. (1) This section applies, and sections 8 to 11 do not apply, if sulphur dioxide from two or more sources of contaminant mentioned in those sections is conveyed to a common air pollution control device at a petroleum facility before being discharged into the air. (2) If one or more of the sources of contaminant is a general combustion device, a person shall not discharge or cause or permit the discharge of sulphur dioxide into the air from the air pollution control device if the concentration of sulphur dioxide at a measurement point in respect of the air pollution control device exceeds, (a) 20 parts per million by volume of sulphur dioxide, averaged over any three-hour period; or (b) 8 parts per million by volume of sulphur dioxide, averaged over any 365-day period. (3) If subsection (2) does not apply and one or more of the sources of contaminant is a thermal cracking unit, a person shall not discharge or cause or permit the discharge of sulphur dioxide into the air from the air pollution control device if the concentration of sulphur dioxide at a measurement point in respect of the air pollution control device exceeds, (a) 50 parts per million by volume of sulphur dioxide, averaged over any seven-day period; or (b) 25 parts per million by volume of sulphur dioxide, averaged over any 365-day period. (4) If subsections (2) and (3) do not apply and one or more of the sources of contaminant is a sulphur recovery unit with a design production capacity of greater than 20 tonnes per day, a person shall not discharge or cause or permit the discharge of sulphur dioxide into the air from the air pollution control device if the concentration of sulphur dioxide at a measurement point in respect of the air pollution control device exceeds 250 parts per million by volume of sulphur dioxide, averaged over any 12-hour period. (5) If subsections (2) to (4) do not apply and one or more of the sources of contaminant is a fluidized catalytic cracking unit, a person shall not discharge or cause or permit the discharge of sulphur dioxide into the air from the air pollution control device if the concentration of sulphur dioxide at a measurement point in respect of the air pollution control device exceeds 75 parts per million by volume of sulphur dioxide, averaged over any 365-day period. (6) If subsections (2) to (5) do not apply and one or more of the sources of contaminant is a Houdry catalytic cracking unit, a person shall not discharge or cause or permit the discharge of sulphur dioxide into the air from the air pollution control device if the concentration of sulphur dioxide at a measurement point in respect of the air pollution control device exceeds 150 parts per million by volume of sulphur dioxide, averaged over any 365-day period. (7) If subsections (2) to (6) do not apply, a person shall not discharge or cause or permit the discharge of sulphur dioxide into the air from the air pollution control device if the concentration of sulphur dioxide at a measurement point in respect of the air pollution control device exceeds 2,500 parts per million by volume of sulphur dioxide, averaged over any 12-hour period. Other Performance Limits