Laboratory furnace equipment is used in petroleum analysis, chemical analysis, and annealing to heat objects to high temperatures while protecting them from airborne contaminants and moisture. A variety of furnace styles are used for performing different kinds of tests, including ashing of organic and inorganic materials, gravimetric analysis, ignition tests, and determination of volatile and suspended solids. Furnace accessories help to protect and extend furnace capability with temperature sensors and controllers, shelves, and hearth trays. Heat blocks have a series of wells that hold a specific size container or test tubes in continuous contact with well walls, ensuring a consistent temperature. Most blocks have a thermometer well that measures temperature at the middle of the block to monitor temperature throughout the block.