Fire resistance is often claimed and rarely verified. A board is only truly "fire-rated" when its behaviour is confirmed by a standard laboratory test.
What the core does
In fire-rated boards the gypsum core contains fibres and mineral additives that delay heat transfer. Water released from the gypsum crystals also absorbs energy and slows the temperature rise.
Reading the certificate
Always check the test standard, the tested thickness and the failure time. OPAL's 15 mm fire-rated board is tested up to 120 minutes under the Iranian national standard.