Burning paper and liquids put through mail apertures in doors and walls can have devastating consequences, especially if premises are occupied. Nocturnal arson attacks on homes can be particularly worrying for domestic residents. The Envirograf® rigid firebox or flexible firebag protects mail slots, so homes and businesses can have the confidence that their premises are guarded against damaging and disruptive arson attacks. These products are safe to use because they do not contain liquids or gases. The intumescent lining puts out the flames..