Chemteq is a manufacturer of filters and carbon adsorbers replacement indicators for toxic chemicals In air. Indicators change color when filter or carbon adsorber is saturated and exhausted. They are very sensitive to target chemicals; color change occurs at or below OSHA and HSE permissible exposure limits. Filter replacement indicators are available for acid vapors, basic and ammonia vapors, formaldehyde, hydrogen sulfide and others.We also manufacture custom colorimetric indicators for a wide variety of toxic chemicals in air including Aromatic diisocyanates (e.g. TDI & MDI), Hydrazines and Phosgene.