Apparatuses for increasing the effective size of gas-entrained particles in a particle detector are disclosed. In one embodiment, an apparatus comprises an evaporation chamber, a condenser in fluid communication with the evaporation chamber, and an inlet in fluid communication with the condenser for receiving a stream of sample gas containing gas-entrained particles. The evaporation chamber includes a heating element and a porous support surrounding the heating element. The porous support carries thereon a working fluid, and the heating element vaporizes the working fluid to form vapor within the evaporation chamber. The porous support may include a portion which extends into a working fluid reservoir.