BET Surface Area Analyzers All NOVA models can produce BET surface area results using the classical helium void volume method, or via the patented helium-free method. Pore Size Analyzers Every NOVA is also a pore size analyzer capable of measuring both adsorption and desorption isotherms in a few hours, completely unattended. Pore Size Analyzers Every NOVA is also a pore size analyzer capable of measuring both adsorption and desorption isotherms in a few hours, completely unattended.