A small number of portable vaporizers provide convection-style heating, which means that the dry herbs do not come in direct contact with the heat source. Instead, the heating element superheats the air within the chamber when activated, and the hot air is manually drawn over the herbs by the user. Because of the fluid nature of the hot air, convection-style heating elements generally provide a more even distribution of heat than conduction-style heating elements. However, they are also more prone to heat loss, as the heat that vaporizes the herb has been carried away from the heat source.
Whether conduction-styled or convection-styled, the vast majority of portable vaporizers require the user to manually draw the vapor from the heating chamber, as opposed to the rarely seen forced air method, which utilizes a fan to pump the vapor from the chamber and is more closely associated with desktop units that use a balloon bag to collect the vapor.