Fire will follow any combustible path it can find. Experience has shown that duct materials may transmit fire from one area to another, even when they have obtained relatively low flame spread ratings from certain test methods. Ducts that are certified by FM Approvals are evaluated to determine they limit that path and challenge the fire spread. Ducts which have been certified by FM Approvals are intended to decrease the risk that the fire will propagate throughout the facility. FM Approved ducts are designed for use without the need for automatic sprinkler protection provided that manufacturer’s instructions are followed.

There are three basic classifications of ducts which have been certified by FM Approvals:

  • Fume exhaust only
  • Fume and/or smoke exhaust
  • Fume and/or smoke exhaust for use in cleanrooms