C-W-Z tests are referenced in BS: 6387, which is called for by cable standards such as BS: 7846. These letters refer to standards of fire resistance
- C – Test with fire only.
- W – Test with fire and water spray.
- Z - Test with fire and mechanical shock applied simultaneously during burning.
To meet the "C" category the cable has to maintain circuit integrity while subjected to fire at 950°C for three hours. To check “W” category, the cable is sprayed with water while also subject to fire to simulate the effect of an activated sprinkler system. In the “Z” category, the cable is subjected to mechanical shocks during the fire test to simulate falling debris. During all of these tests the cable carries electricity at rated voltage.
These tests are highly significant as they actually simulate the fire conditions under which the FR Cables are expected to perform.