Yup, smoke alarms detect suspended particles (visible or invisible) in the air. These particles need not necessarily be smoke particles either. There are two basic types of smoke detectors, ionization and photo-electric. Most folks use ionization...it's the most common detector. They both serve the same purpose using different detection methods. Both detection methods are effective as long as they are UL/ULC rated. The inonization unit uses a minute amount of a radioactive substance (age prevents me from remembering the name of the substance) that keeps the air in the chamber conductive between the negative and positive posts powered by the battery. When suspended particles enter the chamber, the current drop between the posts causes an alarm.
The photo-electric acts in much the same way except it uses a light emitting diode (LED). It sends a light signal to what looks like a 'T' thingie and when particles enter the detector, it scatters the light, causing an alarm.
Not only smoke will trip smoke detectors...dust will as well.
Keep the batteries new and all should be good. Wayne has the right idea on why the detector is tripping. BTW, if the detector is 10 years old or more, replace it.