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No, those are not space guns you're seeing on top of new NYC buildings

If you've looked at the top of Hudson Yards or other new buildings in NYC recently and wondered, "what is that?" we've got the answer.

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2019
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If you have looked up at some of New York City’s newest residential towers like Hudson Yards, you may have noticed something mechanical-looking on the roof that appears to be pointing toward the sky. No, it’s not a space gun. It’s a device called a building maintenance unit.

These are small cranes that are permanently installed for a variety of maintenance uses, but are most commonly used for window washing. They can suspend a human, or robot for those still wanting a sci-fi-esque explanation, down the side of the building. 

The average unit and installation costs from $1 to $2 million, but the dollars don’t stop rolling there. BMUs must be inspected and re-certified annually, to the tune of $10,000 to $20,000 and they require bi-annual cable replacement, which costs $10,000 to $20,000. 

The Department of Buildings and the state’s Department of Labor don’t require BMUs to be used for cleaning windows on towers, but new buildings—especially modern designs with steeply pitched roofs—are adding them because they do the job more efficiently and allow workers to reach parts of a building that might otherwise be inaccessible.

They cut the time it takes to wash a building and do other maintenance, like replacing windows and facade panels. Many BMUs can be operated by a remote and have a reach of 130 feet and beyond.