Hydrocarbon sensor and collector

A hydrocarbon sensor and collector. An element that is capable of absorbing and releasing hydrocarbons is positioned in the air intake system of a vehicle, upstream from the engine and wholly in the airflow. The element has a plurality of chambers defined in it that allow air to pass through the element. The hydrocarbon sensor and collector also includes a means for detecting the level of hydrocarbons absorbed by the element, for example wires 18 used to measure the resistance of the element. The element may be made of carbon, or carbon plus a binder material, and may additionally serve to condition the air flow in the intake. The element absorbs hydrocarbons that escape from the engine when it is switched off, but is regenerated by releasing them into the intake air stream when the engine is running.