How old are your smoke alarms?
It is recommended by Australian Standards and Fire Departments that smoke alarms be replaced after 10 years.
Both hard-wired and battery operated smoke alarms are manufactured to have a recommended service life of at least 10 years under normal conditions of use (AS3786)
After 10 years smoke alarms may malfunction and their efficiency compromised with accumulated dust, insects, airborne contaminents and corrosion of electrical circuitry.
A smoke alarm constantly monitors the air 24 hours a day. At the end of 10 years, it has gone through millions of monitoring cycles. After this much use, components may become less reliable. This means that as the smoke alarm gets older, the potential of failing to detect a fire increases.