Contamination risk under a commercial lease is shaped by the site's condition and history, the proposed use, any proposed works, the parties' knowledge and control, applicable law, and lease drafting. This guide focuses on the negotiation of provisions relating to liability for contamination in a new commercial lease. It does not address environmental issues unrelated to contamination except where other lease provisions or regulatory regimes can affect that liability allocation. Aims of the parties Landlord aims The landlord will seek to minimise its liability exposure and also protect the property, its reversion and the wider estate from contamination risk during and after the term by: • avoiding responsibility for contamination beyond the risk accepted in the heads of terms • making the tenant responsible for contamination introduced, caused, knowingly permitted, mobilised or aggravated through the tenant's use, works or controlled persons • preventing unapproved ground disturbance and obtaining effective rights to investigate, monitor and respond to suspected contamination • securing prompt notification, remediation and an appropriate indemnity for tenant-attributable contamination • preserving