When painting the door edges there is no evidence to
suggest that over-painting of the intumescent seals
by conventional paints or varnishes, in normal
thicknesses, has any particularly harmful effect.
Indeed, such painting can provide added protection
to the seals
There is no evidence to suggest that overpainting of
heat activated seals has any detrimental effect on
the ability of the seals to perform efficiently. There
are some benefits in overpainting the seals as they
are less likely to absorb atmospheric moisture.
However, there are limits on how much paint can be
applied without there being a risk of the seal being
rendered inoperative. It is recommended that
overpainting be limited to a maximum of five coats
of conventional oil bound paint or varnish.
When preparing a frame for redecoration, the use of
heat or chemical strippers should be avoided if
intumescent seals are incorporated. If seals are
damaged by either of these processes, they should be
replaced here is an extract from BS8214 hope it helps