CREATE TABLE table_204_909 (id NUMBER, "pollutant" CLOB, "units" CLOB, "emission standard" NUMBER, "coal-fired" CLOB, "petroleum coke-fired" CLOB)

which pollutant had the same emission standard as pm10 ?
SELECT "pollutant" FROM table_204_909 WHERE "pollutant" <> 'pm10' AND "emission standard" = (SELECT "emission standard" FROM table_204_909 WHERE "pollutant" = 'pm10')
SELECT "pollutant" FROM "table_204_909" WHERE "emission standard" = (SELECT "emission standard" FROM "table_204_909" WHERE "pollutant" = 'pm10') AND "pollutant" <> 'pm10'