Gas mask in a dream: what does it mean?
A device that lets you breathe where the air will kill you is a bleak piece of equipment, and dreams tend to notice the sound of breathing inside it.
How do the four traditions read it?
Each reading below comes from a named tradition and a cited source, so you can see where it came from and decide what fits your dream. The four often disagree, and that is the point: a symbol rarely means one fixed thing, and the distance between Freud, Jung, modern research and myth tells you more than any single verdict could.
Freud
Freud would attend to the mask as much as the air, since a dream that covers a face in order to preserve breathing has done two things at once: protected the dreamer and removed their features.
After Freud, The Interpretation of Dreams (Brill trans., 1913), public domain.Jung
For Jung the protective mask can image survival bought at the cost of recognisability, and the isolation people report inside one, the sound of their own breath, is usually the reading.
Our summary of a Jungian reading, in our own words, not Jung's. See Jung, ed., Man and His Symbols (1964).Modern
Under the continuity view this usually arrives through history, film and school lessons, and clusters after news of chemical incidents. For anyone who has actually needed one, it is memory rather than symbol and belongs with a person.
Our summary of the continuity hypothesis, named by Calvin Hall and Vernon Nordby, The Individual and His Dreams (1972). Its correct scope is disputed; see Domhoff (2017) and the replies to him. Our summary of threat-simulation theory. See Revonsuo, Behavioral and Brain Sciences 23(6), 2000, 877-901. The theory is contested.Mythological
There is no old folklore here. The object is a twentieth-century response to a twentieth-century weapon, and the history attached to it, including its use in the Holocaust, is recorded rather than mined.
Rosmerta Publishing editorial synthesis (after Brewer). The Holocaust is not from Brewer, who died in 1897; that is ours.How can writers use this symbol?
The same symbol, read as craft material rather than as a dream. What it does on the page, how genres use it differently, and what happens when you turn it inside out. Written for novelists, screenwriters and poets who need the symbol to actually work, and it ends with something to try.
In literature
The gas mask is one of the defining images of the last century and fiction uses it mostly as costume, which is a poor return on an object with that much documented history behind it.
Rosmerta Publishing editorial synthesis. Our own words; no quoted text.What it does in a story
It removes a character's face and voice while keeping them alive, which is a strong and uncomfortable combination. Structurally it makes dialogue difficult, which is often the point.
Genre conventions
War writing uses the drill. Dystopia uses it as uniform. Literary fiction uses the civilian issue, the child's mask, which is where the horror is domestic and worst.
How to subvert it
Write a fitting session for children's masks in 1939, conducted cheerfully by somebody who knows exactly why.
Try this
Write four hundred words from inside one. Only breathing, condensation and restricted sight.
Only the first of these names a source. What a symbol does in a story, how genres treat it, how to invert it and what to try are our editorial judgement as writers and editors, not findings from a body of research. They are offered as craft opinion and should be argued with.