# H(curl) conforming Nédélec-Elements to satisfy div(B)=0

Most authors are very clear that it's very dangerous to just use $\mathrm{H}(curl)$ conforming edge elements, which are divergence free, to satisfy $\mathrm{div}(\mathbf{B})=0$ and implement this condition in no other way. I just don't understand why. Could anyone explain in which case this could fail or point me to some good source explaining in which case $\mathrm{H}(curl)$ conforming Nedelec Elements would fail to satisfy $\mathrm{div}(\mathbf{B})=0$ and why?