Investigations were performed on the aging of five activated carbons in the containment exhaust air of an FRG pressurized water reactor over a period of three months to determine whether longer stay times can be obtained with activated carbons other than that usually employed [207B (KI)] in the Federal Republic of Germany. The aging with respect to the retention of methyl iodide (CH3131I) was smaller with activated carbons impregnated with KIX only than with those impregnated additionally or exclusively with a tertiary amine (e.g., triethylene-diamine). It appears that, for the exhaust air examined, no significantly longer stay times can be presently obtained with activated carbons other than 207B (KI).