Litmus Leak

Gas masks (known in the business as "respirators") must be custom fitted. This is understandable--everone's face is a different shape, and even a small leak might have deadly consequences. As such, various mechanisms have been invented to test the fit of a respirator. The most common of these involve exposing the prospective owner to a gas of some kind, which the wearer will be able to detect. This is commonly a type of banana extract, with a strong but not unpleasant smell--if you can't smell it while wearing the respirator, then it fits.

This leads to problems, however; fitting a respirator is a tedious business, and many people are under pressure to get theirs fitted and get on to business, to the point that some people fear losing their jobs if they can't get a respirator in an expedient manner. This sometimes leads to people lying about their fit--saying that the respirator fits properly when in fact it does not, which is obviously potentially quite dangerous.

One solution to this problem was the use of what is called "irritant smoke"--think basically tear gas. If you can smell this stuff, there's no way you can hide it from the testers. The problem with this, of course, is that it is extremely unpleasant, especially when you may have to try a large number of masks before finding one that actually fits.

My proposal: A small, chemical-imprgnated slip of paper similar to a litmus paper, with post-it type glue on the back. The paper has a chemical on it that quickly and visibly reacts to a nontoxic and not-unpleasant-smelling gas (such chemical combinations are already known and are ustilized in simple testing mechanisms). Just stick the paper to the inside of the mask, vent the testing gas, and a wait a few moments before removing the mask and checking the paper for the distinctive color change. It's neither unpleasant or possible to lie about.