The Holtzman Shield in Dune works by blocking the movement of objects faster than certain threshold. This has rendered projectile weapons obsolete in universe and combat has become primarily melee.

The root mean square velocity of air molecules at 25 degree Celsius is about 500m/s.

In the 2021 movie,

Baron Harkonnen was able to escape the poison gas using his personal shield albeit almost suffocated in the process.

Is there any discussion of the gas permeability of the Holtzman Shield in the text? If so, was the shield gas permeable?

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    Not all molecules in a gas have the same velocity. RMS velocity implies that many of them are slower than that, although I don't know what the distribution might be. Commented Mar 14 at 14:21
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    @CristobolPolychronopolis The velocity distribution is of course given by the Maxwell-Boltzmann distribution. This is pretty much the "normal distribution" for high count of particles. Finding a molecule slow enough to go through the shield is rare, in fact only a very cold gas will seep through it. The Holtzman Shield could be used as a heat pump, or, if it uses less energy than it takes to concentrate heat on one side, a Maxwell's Demon giving free energy! Commented Mar 15 at 12:28
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    @DavidTonhofer Sounds like a concept for a Dune fanfic! Maxwell's Demon opens a whole range of technological improvements. I wonder if it can be tuned to allow only objects with a velocity greater than a specified level? Is it symmetrical in both directions? If so, the demon might need some additional help. Commented Mar 15 at 14:54

2 Answers 2


When Gurney Halleck fights with Paul in the beginning of the book, Paul notes that the air within the shield bubbles starts to "grow stale" as the fight goes on. He attributes it to the "slow interchange barrier":

Around the room they fought — thrust and parry, feint and counterfeint. The air within their shield bubbles grew stale from the demands on it that the slow interchange along barrier edges could not replenish. With each new shield contact, the smell of ozone grew stronger.

So the answer would be yes, albeit slowly.


When the Baron realises he'd unintentionally left his shield partially on, this had slowed the gas enough that others in the room suffered/died but he did not. He was then able to escape but just holding his breath rather than nearly suffocating himself (as in the film).

He could analyze it now. His shield had been activated, set low but still enough to slow molecular interchange across the field barrier. And he had been pushing himself away from the table…that and Piter’s shocked gasp which had brought the guard captain darting forward into his own doom. Chance and the warning in a dying man’s gasp—these had saved him.

I don't recall that there was any other specific discussion and, to be accurate, this in the book is the Baron's own speculation on how he survived rather than a statement on how the shields work.

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    I've taken the liberty of swapping in the book quote you're referring to
    – Valorum
    Commented Mar 13 at 16:43
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    Thanks @Valorum! I actually think @fez's answer is better as the quote is a statement from the author rather than the Baron's - albeit well informed - speculation.
    – AdamT
    Commented Mar 13 at 17:33
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    The Baron would surely know precisely the strengths and weaknesses of a shield.
    – Valorum
    Commented Mar 13 at 22:19
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    I always thought that the Baron's body weight helped him as well... The toxic dose for small people is much lower then the toxic dose for large people. And the Baron was extremely obese.
    – Questor
    Commented Mar 14 at 15:12

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