Your smoke detector can go off without there being any smoke. There may be several causes for this.
1. The smoke detector is in a bad location
Install the smoke detector at least 6 metres (20 feet) from appliances such as boilers/stoves and ovens that produce combustion particles. Smoke Alarms should be located at least 3 metres (10 feet) from damp areas such as bathrooms and laundry rooms, at least 1 metre (20 feet) from heaters, 0.50 metres (20 feet) from a light fitting and 1.5 metres (20 feet) from a fluorescent light fitting. Air currents from fans, doors and windows should be avoided. Water vapor and gases can falsely set off a smoke detector because the particles are approximately the same diameter as the smoke particles the smoke detector is trying to detect.
2. The sensor chamber is dusty or dirty.
Smoke Alarms may look clean, but dust can build up on the inside of the cover and make the detector more "sensitive. Clean the detector at least once a month by gently brushing over the smoke detector with the brush attachment of the vacuum cleaner.
3. Insects cover or clog the sensor chamber
Clean the Smoke Alarm with the vacuum cleaner brush attachment. Treat the area with insect repellent to correct this problem. Caution: do not spray on the smoke detector itself.
4. Battery is low
Are you sure the detector is actually triggering a false alarm and not a "low battery" signal? Check your detector's manual to find out what this signal should be.
5. The detector is defective
Detectors also sound an alarm if they are technically defective. In this case your detector needs to be repaired or replaced.
Want more information?
Then be sure to check out the articles "how to maintain and test the smoke detector?".