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Faraday Cage Question? Answered

I know a faraday cage blocks electric fields and waves and such, but does it also block charged ions.... things such as ozone, perhaps?

Probably a stupid question, but its late and I'm tired. Probably not thinking straight.




8 years ago

if the ion has the same charge as the cage it will be repelled. Unlike electricity which will take the easiest path (thru the cage surface) the ions may make their way between the charged bars.


Answer 8 years ago

Having used tektronix. scope instruments in room sized faraday cage I can attest the scopes create, add and hold charges inside the cage.
This means you can get at some dangerous potentials inside the cage.
My cage was used to lower external background stray E-fields from contributing errors to usec signal event integrators.

Accumulations of ionized gas can collect inside a cage. Ozone is a high energy unstable bond (not ionized) of three oxygen atoms
(with a half life of about 26 min) Ozone easily ionizes and will vigorously combine with remnants of burning material to form CO2. We can smell
Ozone and in large concentrations Ozone will grab a red blood cell and
not let go, eventually suffocating a person very much like carbon_monoxide,
Oxygen is a stable normal diatomic two oxygen molecule that we breath .

Faraday Cages protect you inside from external E-fields outside and depending on the size of the mesh certain EM radiation waves are attenuated and blocked.

Slowly changing & static magnetic fields pass right through a Faraday Cage.


8 years ago

You are mixing up phenomenon a bit.

Electric waves are essentially immaterial. The E-M energy is stored in the wave, not in an atom.

Ions are atoms that have lost / gained some energy, elevating or stripping the electrons around the atom to a new level. This is not the same as having a free electron. It is an atom that has a bit more / less electric potential, but still an atom.

E-M waves would like to ionize atoms. Ionized atoms want to chemically bind to oppositely ionized atoms.

Metal can accept almost any E-M energy to ionize some part of the metal matrix, and thus blocks E-M waves in the case of a Faraday cage. Metal may or may not chemically interact with ionic atoms. Plus the ionized atoms still need to physically contact the Faraday cage, which may or may not happen.

Ozone, a gas at STP, will diffuse into any other volume of gas. If a Faraday cage is present in that volume, ozone ions could slip through by not bumping into the metal. If you made a solid metal box, instead of a mesh Faraday cage, you'd catch all the ions- and see the metal oxidizing!

SO, long story short:
E-M waves will be intercepted by a tight enough mesh.
Gases of ionized atoms may slip through.


8 years ago

Ozone isn't charged. It's a metastable molecule (O3), and electrically neutral. As Frollard said, a Faraday Cage will stop ions with the same charge as the cage. If you put the cage at positive voltage, it'll prevent the flow of positive ions (and similarly for negative). If the cage is grounded, it'll still do a fine job of shielding you from RF, but ions will drift through just fine.