Within the context of property leases, landlords and tenants have certain duties to one another.
With both commericial and residential leases, the covenant of quiet enjoyment is an implied promise in every lease that neither the landlord nor anyone under the landlord's control will interfere with a tenant's possession or enjoyment of the premises.
Similarly, the implied warranty of habitability is an implied promise in residential leases only that the landlord will provide, throughout the lease period, premises that are safe, fit, and clean for human habitation.
In both cases, a constructive eviction cause of action is triggered if the landlord is at fault by causing substantial interference with the tenant's use and enjoyment of the property so severe that the tenant ends up vacating the property, the tenant's obligations to pay rent are excused and additional remedies, like damages, may be available.
In general, issues that arise with respect to health and safety, or violated building codes for instance, are often indicative of a breach. Typical triggers for constructive evictions include scenarios that no reasonable human would endure due to either safety or cleanliness.
(1) Tenant discovers a mouse infestation in her apartment. She complains to the landlord who fails to remedy the situation. Because of the mouse infestation, tenant cannot remain in her apartment, so she leaves. At this point, she is excused from paying rent and my collect damages.
(2) Tenant discovers a leaking oil tank in his restaurant basement that landlord cannot repair. If he leaves within a reasonable time, he will be excused from his lease obligations and may collect damages; crucially, however, if he does not leave within a reasonable time, then this remedy may not be available to him.