As Nest prepares to ship its Protect smart smoke detector, it's been hit with a patent lawsuit from one of its competitors. BRK, which sells the First Alert line of smoke detectors to consumers, construction companies, and manufacturers, has asked a court to stop Nest from selling the Protect and require it to pay triple the damages BRK has suffered from allegedly having a series of patents copied by Nest. The features in question are some of the ones Nest has touted as welcome improvements to existing smoke detectors: a voice that will tell owners where it's found smoke and a set of sensitive vents that sit around the rear of the Protect.

"Nest's current marketing campaign incredibly attempts to take credit for Dr. Morris' and BRK's innovations."

The location warning system, BRK says, was laid out in a series of patents that cover using pre-recorded voice alerts to "describe the type of environmental condition detected or the location" of the detector that senses it. That "exclusive" technology was first used in a 2003 smoke detector, and the company says it's sold 1.8 million units with voice and location alarm systems since then. The Protect's rear vents, meanwhile, allegedly infringe on another patent for putting sensors near the mounting surface of a smoke detector. Both features were advertised on BRK's packaging, and the company says that BRK's success has been "a direct result of its innovations;" by extension, Nest's use of them would erode its own position in the market.

As the quote above hints, BRK paints its suit against Nest as the attempt of a proven industry giant to defend itself against a flippant Johnny-come-lately. "Nest's current marketing campaign incredibly attempts to take credit for Dr. Morris' and BRK's innovations, claiming that 'there has been no innovation in the market for years,'" says the complaint. "Had Nest actually participated in the smoke and carbon monoxide alarm market over the last ten years, it would know that the innovations that Nest is taking credit for are in fact BRK's patented technology."

Nest, meanwhile, is no stranger to lawsuits. Competitor Honeywell made practically the same move when Nest launched Its original thermostat, filing suit over patents that it said covered Nest's hardware design and "smart" features. That case is still ongoing, and Nest has already filed a response to BRK's complaint, dismissing it as "broad hand-waving." For one thing, Nest insists that its vents operate in a way that's practically the opposite of the patented system, even if the goal is the same; BRK's system itself, it claims, is also preceded by a patent from the 1970s.

Nest says not only is it not infringing BRK's patents, BRK can't even sue over some of them

Its argument against the voice system is a little different: Nest essentially says that BRK doesn't actually have the right to sue for infringement. BRK's technology was designed by outside inventor Dr. Gary Morris, who then worked with BRK and allegedly gave it an exclusive license to his patents. Nest disputes the "exclusive" claim and then goes even further, saying that Morris himself wasn't in any position to license his work; as a professor at West Virginia University, his patents would have belonged to the university. That's on top of Nest's other defenses, which include denying that BRK has suffered real harm and giving an excruciatingly detailed explanation of how its product doesn't fit the patent claims — the definition of "duration" makes an appearance here.

The first battle is over whether Nest will be able to sell smoke detectors as the lawsuit goes forward, after which the two companies will face off over the long-term future of the Protect. Nest CEO Tony Fadell has previously called Honeywell "worse than a patent troll" for its thermostat suit, and Nest is unlikely to think that BRK is any better.