If you have been using a pod system with draw activation, it is likely that you have experienced an auto-firing or auto-activation at some point in the past. As you may have guessed, this is caused by a malfunction in the draw activation sensor, and can occur when you accidentally blow air into your mouthpiece instead of inhaling or when your device is exposed to extreme wind. There may be other reasons for your sensor to malfunction, but these are the most common reasons.
I once had a Myle device auto-fire on me by accidentally inhaling from the wrong end of the device. If you are unfortunate enough to experience an auto-fire, you can prevent burns and a potential explosion by first removing the pod immediately to stop the flow of electricity and then turn off the device if possible. It is also recommended that you place the device outdoors away from any ignitable material, in case of eventual explosion, and allow it to cool down before picking it up again to put in your hazardous waste bin for disposal.
Most pod systems these days have built-in protections against this scenario which will cause the device to turn off after the fire button has been pressed for 10 seconds, and while that may prevent an explosion, it may not prevent the hot pod / device from burning your hand or leg (if your device is in your pocket when it auto-fires).