Nest Protect has been completely redesigned. It has an industrial-grade smoke sensor, can be hushed from your phone, test itself automatically, and last up to 10 years. It also tells you what's wrong and can even alert your phone.
It is recommended that you place Nest Protect inside and outside any sleeping area, on every floor, and at the top of stairways. There may also be local regulations that you need to follow.
The National Fire Protection Association (NFPA) and the Consumer Product Safety Commission (CPSC) recommend several places to place a smoke and carbon monoxide alarm.
Are there any rooms where installing a smoke and carbon monoxide alarm is not recommended?
Some rooms in your home have conditions that are more likely to damage a smoke and carbon monoxide alarm or set off nuisance alarms.
Regulations recommend against installing combination smoke/carbon monoxide alarms in these rooms:
Can I just replace my existing smoke and carbon monoxide alarms?
Although you may have existing alarms in your home, check the placement of those alarms for compliance with these or local guidelines. Older homes, especially, may not align with current regulations.