parts per million (noun) - a unit for measuring concentration of chemicals or substances (finding how much of some chemical or substance is present) - พีพีเอ็ม (ส่วนในล้านส่วน)
parts per million (noun) - a unit for measuring concentration of chemicals or substances (finding how much of some chemical or substance is present) - พีพีเอ็ม (ส่วนในล้านส่วน)