A filter trap for a motor vehicle thermal device is made of polymer material and includes two longitudinal edges extending along a length thereof connected by two lateral edges extending along a width thereof. The trap includes a first assembly tab extending along the length thereof and fixed to one of the lateral edges. The trap also includes a snap coupling to block the trap. The snap-coupling is fixed to one of the longitudinal edges and is located in the vicinity of another of the lateral edges. The trap also includes a second assembly tab extending perpendicular to the first assembly tab. The second assembly tab is fixed to another of the longitudinal edges and is located in a vicinity of another of the lateral edges. The trap has sufficient flexibility along the length thereof to permit twisting of the trap about a longitudinal torsion axis of the trap.