Nest Protect may have returned to store shelves at a lower price point this week, but the smart smoke protector is also proving how sensors in homes provide invaluable data. Nest Labs has released a new report based on data from hundreds of thousands of Nest Protect devices. The anonymous data shows that carbon monoxide leaks are more frequent than many may have expected, and that at least one million households in the US, UK, and Canada are exposed to high levels of carbon monoxide each year. Around 400 people are killed by carbon monoxide poisoning every year in the US, so Nest’s data could help safety experts better understand why and when leaks happen.

It has been notoriously difficult for experts to analyze carbon monoxide leaks, but Nest is able to provide data on peak carbon monoxide levels, the length of events, and stats on how many homes experienced issues over a period of months. It’s all valuable and comprehensive data, but it does raise some privacy questions over how these types of sensors will be used in homes in the future. Gizmodo points out that the Nest Protect includes heat, light, motion, and ultrasonic wave sensors that could all be used for more than just smoke detection. Right now Google owns Nest and neither company is planning to use the data more widely, but as these sensors become more common it’s possible that your smart home could be the next battleground for companies to learn about your life and habits.