Option to avail exemption: written option must be filed before first clearance; special window allowed for existing units. The amending notification requires a written option to avail exemption to be exercised by the manufacturer before effecting the first clearance and is effective from the date of exercise. Units already operating under the June 2003 notifications as of 5 November 2003 had until 30 November 2003 to submit the written option; units not yet effecting their first clearance may submit the written option any time in the current financial year, provided it is submitted before their first clearance.