The present invention relates to a hydrocarbon trap positioned in the air intake system of a vehicle, upstream from the engine and wholly in the airflow. The hydrocarbon trap comprises a holder and a material for adsorbing the hydrocarbons, inserted inside the holder. The holder comprises a screen that is added at the end facing the engine. The screen is held in place with the help of a locking mechanism. The locking mechanism comprises a locking ramp on the holder and corresponding locking tab on a clamping ring surrounding the holder.