Some may not go off in time
THE MOST COMMON type of smoke detector — ionization — may not save you in “smoldering fires,” those that start out producing little flame but lots of smoke. In a test initiated by NBC Nightly News, more than half an hour passed before ionization smoke detectors activated once a smoldering fire began.
However, photoelectric smoke detectors go off much sooner when there is a smoldering fire, the test showed.
The National Fire Protection Association (NFPA) recommends that both types of detectors be used — ionization, which responds quickly to open flame, and photoelectric, which detects smoke more readily.