Does your passthrough have an in-line battery? The reason I ask is that a passthrough with an in-line battery is providing the atomizer with the voltage from the battery (3.7v)not the USB port (5v). If you have an in-line battery and are enjoying the experience, the USB port is constantly topping off the battery and providing peak power to the atomizer at all times. If you have no in-line battery, you are getting 5v instead of the typical 3.7v from a screw-in battery. Higher voltage creates a warmer vapor and, often, a more satisfying vape. As long as you do not feel your atomizer is overheating (i.e. hot to the touch), enjoy it!