An environmental control for use in air handling systems that are required to provide highly effective filtration of noxious gases is provided. In one embodiment, a filtration system utilizes a novel combination of at least one metal-doped silica-based gel and zeolite materials to trap and/or modify, and remove such undesirable gases (such as ammonia, ethylene oxide, formaldehyde, and nitrous oxide, as examples) from an enclosed environment. The gel component exhibits specific porosity requirements and density measurements; the zeolite component is generally acidic and is preferably not reacted with any salts or like substances. The novel combination of such gels and zeolites permits highly effective noxious gas filtration over a wide range of known toxic industrial chemicals such that excellent breakthrough results are attained, particularly in comparison with prior media filtration products. Also included is the presence of an oxidizing agent on the gel materials to aid in capturing nitrogen dioxide and preventing conversion of such a product to NO. Methods of using and the application within specific filter apparatuses are also encompassed within this invention.