The thermos fires a blue beam of light that can suck in and capture any ghost, regardless of their size or shape. Danny has been able to capture huge ghosts such as a super-powered Desiree and a reality-warped Freakshow. It is shown that the thermos has no effect on humans or other non-ghost creatures, though it can capture half-ghosts in ghost form.
After capturing them Danny can banish ghosts into the Ghost Zone; they need to escape through a portal if they want to return to the human realm. The way this works is Danny inserts the thermos into the Fenton Ghost Portal, thus sending the ghost back to the Ghost Zone.
When it was first built, it wouldn't function, but by using some of his ghost energy, Danny was able to permanently activate it for the remainder of the series.
The device can hold multiple ghosts at once. After capturing ghosts in the thermos, Danny releases them back into the Ghost Zone through the ghost portal. However, if it is damaged, it can release any and all ghosts inside. Some ghosts are so powerful that they can resist and even break free from containment: Dark Danny was trying to escape the thermos he was trapped in during his last appearance, and the reality-warped ghost Freakshow destroyed the thermos he was in.
The thermos also has a setting called "Reverse Polarity," which Danny demonstrates is a way to close/seal up ghost portals leading between Earth and the Ghost Zone to prevent any ghost monster from getting out. This was only shown in "Claw of the Wild" .
- 101. "Mystery Meat"
- 103. "One of a Kind"
- 104. "Attack of the Killer Garage Sale"
- 106. "What You Want"
- 109. "My Brother's Keeper"
- 111. "Fanning the Flames"
- 114. "13"
- 115. "Public Enemies"
- 201. "Memory Blank"
- 202. "Doctor's Disorders"
- 204. "Reign Storm" (mentioned)
- 206. "Identity Crisis"
- 207. "The Fenton Menace"
- 208. "The Ultimate Enemy"
- 211. "Secret Weapons"
- 213. "Micro Management"
- 219. "Reality Trip"
- 303. "Girls' Night Out"
- 304. "Torrent of Terror"
- 308. "Boxed Up Fury" (mentioned)
- 309. "Frightmare"
- 310. "Claw of the Wild"
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- The Fenton Thermos is based on the ghost trap from Ghostbusters.
- In his first "10 Years Later" video, Butch Hartman upgraded the Fenton Thermos to be more portable by attaching it to the wrist of Danny's glove on his new suit. Once he captures the ghost it is stored in his suit. This built in thermos design is used by Vid from Masters' Blasters in Phantom Planet.