Excise duty cap for pollution-control equipment limits levy to a low ad valorem rate, subject to certification. Exemption from excise duty is granted for specified pollution control equipment by limiting the effective rate of basic excise duty on those goods to 5% ad valorem, subject to certification by an officer not below the rank of Deputy Secretary in the Ministry of Environment and Forests that the goods are intended for pollution control purposes; the Schedule lists eligible air and water pollution control systems, monitoring instruments, treatment and dewatering equipment, and related apparatus.