(CTA). CT angiography is a type of medical exam that combines a CT scan with an injection of a contrast media to produce pictures of blood vessels and tissues in a part of your body. The contrast is injected through an intravenous (IV) line started in your arm or hand.
The only time a landlord must replace the carpet is if it somehow affects the health or safety of the tenants, such as if the carpet is moldy, unsanitary or ripped. The law does not govern aesthetics, so even if the carpet is stained or old, as long as it is in fair condition, the landlord does not have to replace it.
Confidence votes 315. The answer to this question is probably only when the landlord believes that it is to his economic interest to do so. Now I can't say this is absolutely true for all 50 states, because there are some city jurisdictions that require landlords to paint the rental interior every 3 or 4 years. However, for most readers of this answer, this is the exception to the rule.