  CSS codes are in one-to-one correspondance with length 3 chain complexes. The
latter are naturally endowed with a tensor product $\otimes$ which induces a
similar operation on the former. We investigate this operation, and in
particular its behavior with regard to minimum distances. Given a CSS code
$\mathcal{C}$, we give a criterion which provides a lower bound on the minimum
distance of $\mathcal{C} \otimes \mathcal{D}$ for every CSS code $\mathcal D$.
We apply this result to study the behaviour of iterated tensor powers of codes.
Such sequences of codes are logarithmically LDPC and we prove in particular
that their minimum distances tend generically to infinity. Different known
results are reinterpretated in terms of tensor products. Three new families of
CSS codes are defined, and their iterated tensor powers produce LDPC sequences
of codes with length $n$, row weight in $O(\log n)$ and minimum distances
larger than $n^{\frac{\alpha}{2}}$ for any $\alpha<1$. One family produces
sequences with dimensions larger than $n^\beta$ for any $\beta<1$.
