This disclosure describes a personal vaporizer such as an electronic cigarette, electronic nicotine delivery system that includes a movable ceiling, which can be adjusted to compensate for changes in ambient barometric pressure. Personal vaporizers can provide controlled substances (e.g., nicotine, Tetrahydrocannabinol (THC), Cannabidiol (CBD), etc.). In many personal vaporizers, a wick transports the substance to be atomized from a reservoir to an atomization chamber via capillary action. In condition where a sufficient differential pressure between the atomization chamber, typically at ambient pressure, and the reservoir exists, the substance can leak from the reservoir into the atomization chamber without being drawn out by airflow (e.g., the user inhaling on the mouthpiece). A movable wall within the cartridge of the personal vaporizer can be used to adjust the volume of the reservoir, and reduce differential pressure between the reservoir and the ambient pressure, minimizing or eliminating unwanted leaks due to pressure changes.