A portable device includes an outer housing including an inlet port and a outer slot adapted to receive a vapor sensor card; an operating circuit disposed at least partially within the outer housing; a sensor holder at least partially disposed within the outer housing. The sensor holder includes: an inner housing including a gas intake chamber in downstream fluid communication with the inlet port. The gas intake chamber has a gas outlet in fluid communication with an inner slot retaining a sensor card socket for engaging the vapor sensor card. The sensor holder further comprises an electrical heater element, a fan, and a turbulent-flow-inducing member. The vapor sensor card comprises a sensor housing and a capacitive sensor element.