A New York apartment was left in such a vile state that building superintendents had to sport industry-grade hazmat suits just to walk through the front door.

It follows a year-long battle to evict the Lower East Side resident after neighbours complained of a corpse-like smell wafting through the walls.

When eviction was finally secured, Martin Fernandez was tasked with cleaning the roach-infested apartment, but rather than complain about the filthy job, he filmed the clean-up to document the condition of the home.

"Whatever you've seen, you've never seen nothing like this," Fernandez said moments before entering the apartment.

Once inside, rotting rubbish could be seen strewn across the floors and the walls had turned black from where roaches had left their mark.

The biggest surprise came when the cleaning crew lifted the mattress, only to discover a dead cat underneath – already in the process of decomposition.

Fernandez noted how he saw the tenant's condition change over the years.

"This guy was living here for many years," he said. "When I first started doing work [in the building], we gave him a new stove and he was a very clean guy.

"Last two years, this happened. He was sleeping on all that and he thought nothing was wrong and he wouldn't give us access.

"Courts in New York City are basically not in your favour so they allowed him to stay here for over a year living in those conditions.

"Of course, the system will always find an excuse of why they allow them [to stay] but I've never seen a hoarder live in a condition like this where the mattress is rotted and the guy can sleep there comfortably."