A hydrocarbon adsorption unit for recovery of volatile hydrocarbons which emanate from several sources and which would otherwise be released into the atmosphere through the air cleaner of an automobile engine when the engine is shut off. The unit is positioned in the air intake system such that all air flowing through the engine passes through the unit. The unit comprises a housing having an air inlet and an air outlet. The housing contains a substrate and a volatile hydrocarbon adsorber material coated on the surface of the substrate. The adsorber material may be silica gel, a molecular sieve and/or activated carbon. The material further contains a binder that will cause the material to adhere to the surface of the substrate.