Many types of heaters are available for a variety of laboratory heating applications. Multi-purpose block heaters are ideal for incubation and activation of cultures, enzyme reactions, blood urea nitrogen determinations, immunoassays, and melting/boiling points. Burners produce a single open gas flame and are commonly seen in laboratories. Drum heaters provide freeze protection, viscosity control, and materials maintenance at elevated temperatures. Environmental chambers create temperature humidity extremes in chambers. Furnaces are designed for laboratory and industrial applications.