All damage to heat-dissipating armor from heat-causing weapons is halved (round final damage up) and the
heat dealt by such weapons as well as all other external sources (including fire) is reduced to 0. The only exception is magma.
The heat generated by entering or occupying magma hexes is nullified, but the damage is unaltered, and a ’Mech with this armor can still become bogged down in magma.