Why did the smoke alarm not go off when the popcorn burnt?

The smoke alarm may not have gone off when the popcorn burnt due to several reasons. It could be that the smoke was not dense enough to trigger the alarm, or the alarm's sensitivity settings were too low. Additionally, if the smoke alarm was malfunctioning or had a dead battery, it would fail to detect the smoke. Finally, the type of smoke alarm—ionization vs. photoelectric—can affect its responsiveness to different types of smoke.