or a pipe another possibility is a pipe not shown with a stem so constructed that a filter can be inserted therein as an accompaniment to filling the pipe with a fresh charge of tobacco where the red blood cells whether as part of a cigarette filter or in an absorber solution are to be stored for any substantial period of time deterioration of the active components may be prevented or at least delayed by storing the composition under refrigeration for example cigarettes containing such absorber charges could readily be stored under refrigeration the active life of the charge would be further increased by the encapsulation proposed above the terms 34 absorb 34 34 absorber 34 and 34 remove 34 as used herein with respect to the effect of red blood cells on co in a gas are to be understood as encompassing any process which decreases the concentration of co in said gas whether the red blood cells function by absorption or by catalysis of a reaction or by any other means the experimental discovery that a charge of red blood cells could remove from a gas stream a quantity of co up to 4 times as large as could be accounted for on the basis of the hemoglobin present was initially most.