The effects of tritium adsorbed on internal torus and near-torus components in tokamaks are discussed. For in-torus locations, which normally experience plasma particle fluxes, the effects of adsorbed tritium are entirely negligible because of the weakness of the tritium β-decay. Tritium adsorbed on surfaces, however, can dramatically degrade diagnostic devices by causing particle counting backgrounds due to the decay electrons. Experimental data on channel electron multipliers (CEMs) which have been tritium-exposed illustrate this degradation and point out the necessity of determining tritium effects for all particle detector types which will be exposed to tritium in tokamaks.