Helium-3:

Helium-3, produced as microscopic bubbles inside the lattice of tritides, is not released except through fracture and deformation of metal grains. This release commonly occurs at high temperature or after long periods of time.  While a tritide is heated to release tritium, helium-3 is also released to a few extents. The cooled metal, therefore, does not resorb the helium-3. A practice of regenerating a tritide storage bed to erased helium-3 instantly prior to use for pure tritium delivery is thus general.

If helium-3 (or another inert impurity) accompanies tritium gas which is absorbed onto a tritide former, helium blanketing might occur. The absorption rate slows as the concentration of helium in the metal crevices leading toward active sites becomes high.  General gaseous diffusion is frequent not enough to overcome this effect. Forced diffusion through recirculating the gas supply could be used to overcome blanketing.