A fluid treatment system incorporating an integrated heat exchanger and thermal treatment unit. A fan draws or pushes a contaminated fluid through the heat exchanger, which is preferably of the counter flow type. The integrated heat exchanger and thermal treatment unit is fabricated by stacking sheets of metal foil so that gaps are defined between adjacent sheets. These gaps define alternating untreated and treated fluid channels. The untreated fluid flows through the heat exchanger and into the thermal treatment unit, with is disposed within aligned orifices formed in the metal foil sheets. Heat transfer occurs between adjacent treated and untreated channels, which greatly improves the efficiency with which a temperature of the untreated fluid entering the heat exchanger is changed as a result of heat transfer with the treated fluid that is exiting the heat exchanger. A header system is in fluid communication with either all of the treated or all of the untreated fluid channels. The integrated heat exchanger and thermal treatment unit also usable as a chemical reactor to generate a desired chemical product from at least one reactant.