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

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'