Unfortunately CA fumes also have a direct toxicity to all mucosal surfaces independent of allergies. This occurs in the parts per million range and the threshold is only about double what is required to notice the smell (ie 2-4 ppm vs 1 ppm). This can be reduced by good air circulation (fan + air exchange) and maintaining relative humidity at about 45%. Allergies develop after repeated exposure to the fumes, but the risk can be reduced by the same means that reduce toxic exposure. Even wearing a simple mask will reduce exposure due to the trapped humidity increasing the polymerization of the fumes with the surface of the mask prior to reaching your nose or mouth. Doesn't do anything for the eyes though.