Elemental Ghosts are an special type of ghost found in Luigi's Mansion. They require either Fire,Ice, or Water to break their shield, and then let Luigi then suck them up. Touching directly gives Luigi damage (except after they lose power). During Luigi's adventure to save Mario, he encounters Elemental Medals to help him defeat certain ghosts.
Fire Element Ghosts
Fire Element Ghosts can be found in areas like torches and fireplaces. To summon these Elemental Ghosts, Luigi must have the Fire Elemental Medal, obtained in the Mirror Room. The player can use them to defeat Flashes. Fire can also be used to destroy Fake Doors, especially during the blackout. The player has to be extremely careful with fire, because shooting it at objects that explode (example: Spark, Bomb) will cause the object to explode on contact, meaning if Luigi gets too close, he'll take damage.
Water Element Ghosts
Water Element Ghosts can be found in places like bathtubs, sinks, and other places with water. The player will need the Water Elemental Medal, found in the Kitchen. Luigi can use them to defeat Temper Terrors, water plants, put out door fires, extinguish Sparks, or even use it to defeat Sue Pea. The Water Elemental Ghosts are also needed to obtain one of the 2 Gold Diamonds.
Ice Elemental Ghosts
Ice Elemental Ghosts can be found in places that are cold or in a freezer. The player will need the Ice Elemental Medal, found in the Tea Room. They can be used to defeat Blue Blazes, freeze other ghosts, defeat Miss Petunia, or freeze the water in the Pipe Room.