The persistent use of chemical warfare agents (CWAs) by rogue states in current conflicts provides a reminder that these hazards remain a real threat. Although hazmat suits made of fully impermeable barrier materials provide an effective means of protecting against CWAs, they also inhibit evaporative cooling which can cause rapid hyperthermia. This conundrum has motivated a search for novel materials that allow water vapor but not CWA permeation. Here we show that, at least for aerosolized CWA, this can be achieved using a highly breathable composite fabric that self-seals only when exposed to target chemicals. Our approach is based on the use of selectively superabsorbing polymer (SAP) microbeads that are dispersed on a highly breathable fabric. Many CWAs, especially nerve and blistering agents, have low vapor pressure and are typically dispersed as a "fog"via aerosolization. We show that upon contact with an example organic aerosol (o-xylene) the proposed SAP microbeads dispersed on a nylon mesh rapidly swell, seal pores in the material, and inhibit passage of the microdroplets. In contrast, the SAP microbeads do not swell on contact with water and provide a water vapor permeation rate of over 10 kg m-2 day-1, comparable to a cotton shirt.