Abstract: A boiler for generating vapor at low pressure from liquid in reservoirs that are not pressurized is provided. Liquid from a reservoir is fed through a supply wick by capillary action to a boiler wick in which the liquid is heated and boiled to a vapor. The heat for vaporization is transmitted by a porous hot seat which sits atop and is in contact with the boiler wick. The boiler wick and hot seat are contained within an insulating cylindrical shroud, which forms a tight seal with the edges of the boiler wick. If the liquid to be vaporized is a fuel for a burner, then combustion heat can be used to supply the heat to the boiler. A resistive heat source can also be used to heat the hot seat and boiler wick.