According to our lab tests, the Nest Protect does a superb job at detecting smoky, smoldering fires and low levels of carbon monoxide (100 parts per million). Its performance at detecting high levels of CO (400 parts per million) falls in the middle of the pack. But it does a poor job of detecting fast, flaming fires with minimal smoke, typical among photoelectric smoke detectors. Given that flaming fires (for instance, a cooking fire) are common, we recommend either using a dual-sensor (both photoelectric and ionization) alarm or pairing the Nest Protect smoke alarm with an ionization smoke alarm, which detects flaming fires. A good option is the Kidde i9010 (Battery), $20. Google claims that the Nest Protect uses a special “split spectrum” photoelectric sensor to help it detect both smoldering fires and flaming fires, but our testing didn’t back that up.
On the home front, we’ve used multiple Nest Protect alarms in five rooms for over three years, and we’ve found the features useful. Setup takes about 15 minutes per alarm, and we’ve found that we can cook bacon without fear of the alarm scaring the kids and pets. The Pathlight was a tad too bright for bedrooms at night, but at least we were able to turn them off. What we like best about the Nest Protect? The alarm notifications, which provide peace of mind when we’re on vacation.