Public liability clause excluding liability for pollution and contamination unless caused by a sudden, identifiable and unexpected incident ‘happening in its entirety at a specific time and place during the period of insurance. All pollution/contamination arising out of one incident is deemed to take place at the time of the incident. The clause is more widely used than SEPTIC. The aim is to exclude gradual pollution from the cover. See ENVIRONMENTAL IMPAIRMENT LIABILITY; POLLUTION INSURANCE.