It is called BDSM. For those of you who are unfamiliar, BDSM is a complex acronym that represents many different activities within the kink practices, for example: Bondage and Discipline, Dominance and Submission, and Sadism and Masochism... I say it is complex because this acronym has dual meaning in some aspects.
In any event, power play is a huge aspect of the BDSM phenomena and it is in this practice that the gas-mask has reached further iconic status.
The advent of gas mask in art is not a new phenomenon, the Mystery, power play differentiation, and ambience of the man in the mask has been around for a long time. However the gas mask as a sexual stimulus is fairly new and surprisingly it is showing up in modern-day erotica.
For some reason there is something appealing about sexuality and anonymity. Researchers would theorize perhaps that it is the concept of sexual aggression that is free from the responsibility of morality, a trace of evolutionary ancestry perhaps on one end of the spectrum, and a testimony of the sinful nature of man on the other.
In any event it is hard to deny the draw of silken bare skin that is somehow more accessible without the responsibility of placing a face or any emotion to it. It is this anonymity that draws so many from the BDSM community to gas-masks and masks in general; the notion of sinful delight in the flesh of another without the responsibility of the causal effect of your acts on them as a person.
The effect it seems, on a root level, is to objectify the wearer into a sexual object as opposed to a sex partner. It is this power play that appeals to the artists who portray the gas-mask erotica that is somehow so appealing, even to many who are not into the lifestyle.
This type of erotica is being capitalized on by Hollywood as well. Series such as American Horror Story seek to bring erotica and bondage along with power play to a new level, that of an every day entertainment source that is in every American home.
One thing is certain, the icon of the gas mask in America has changed and evolved, from a source of fear inducing anonymity to a sexually charged catalyst of powerful proportions.