The Anti-Dioxin Filter is a ship part found in Pikmin. It is one of the vital parts of the S.S. Dolphin and Captain Olimar is unable to leave the planet without it.
How to Get
The Anti-Dioxin Filter is found in a large lake in the Forest Navel and protected by multiple Wollywogs so bringing at least 40 Blue Pikmin is mandatory to retrieve it.
"It's the Anti-Dioxin Filter! This fits over the rocket's exhaust port and filters out all disease-causing agents from the ship's exhaust. That means I'll be able to move around without polluting the planet's atmosphere! I feel worlds better!"
"The laws of deep space require all ships to eliminate all pollutants."