An apparatus and method are described for removing vapor phase contaminants from a gas stream by placing a porous tube having a sorbent material into ductwork through which the gas stream passes. In a first mode of operation, vapor phase contaminants are adsorbed by the sorbent. In a second mode of operation, the porous tube is cleaned of any accumulated deposits, for example fly ash, while in place without having to stop the gas flow. In a third mode of operation, the sorbent can be regenerated in place and without having to stop the gas flow by heating and collecting the desorbed contaminants. This invention is particularly suited for the removal of vapor phase mercury from flue gas generated by a combustion process.