What happens to the chlorine in epichlorohydrin when a two-part epoxy is air-cured?
There is little if any chlorine in a epichlorohydrin / bis phenol A expoxy resin, it is normally lost during production as sodium chloride into the aqueous phase while the resin forms an organic phase.

The normal way to make the resin is to react bisphenol A with sodium hydroxide and the epichlorohydrin. What happens is that a mixture of the three reagents and water is heated up together. The phenol groups on the bisphenol A are deprotonated and then they attack the epichlorohydrin to then form 2,2'-(((propane-2,2-diylbis(4,1-phenylene))bis(oxy))bis(methylene))bis(oxirane). The epoxide (oxirane) groups in this then react with phenolate anions from new bisphenol A molecules to form 4,4'-((((((propane-2,2-diylbis(4,1-phenylene))bis(oxy))bis(2-hydroxypropane-3,1-diyl))bis(oxy))bis(4,1-phenylene))bis(propane-2,2-diyl))diphenol. The unreacted phenol groups on this then are reacted with more epichlorohydrin to form new reactive groups.

This reaction continues on and on to form a polymer, it is normal to use a small excess of epichlorohydrin to give a epoxy terminiated polymer (resin). This is then reacted with a cross linking agent such as an amine to form the final epoxy. As a result the chlorine content of the epoxy should be very very low.