I spoke to Rutland's Technical department ( the manufacturer of Chimfex) when I was working on the Heating with Wood DVD Set. I researched this product and a lot of other information about chimney fires because I wanted to be sure I had the facts for the DVD. Here are some helpful tips I found during this project:
The principle use of chimfex is exactly what the packaging states. It's a fire SUPPRESSANT. It's not labeled extinguisher but suppressant. In this case it means: To reduce the incidence or severity of (an appetite or cough, for example); The chemical in Chimfex when burned, robs the environment of oxygen and suppresses the fire.
I would not totally rely on the product to put the fire out but dramatically slow the fire down so when the fire department arrives it's just the chimney on fire or smoldering and not the house as well. You should still call 911 for the Fire department. Time is critical in a chimney fire. Get your family to safety, Call 911, Throw in a chimfex if you have one, completely close off the air control to the appliance if you can, and evacuate the structure.
I think wet rags, wet newspapers, plywood covering fireplaces is just bad advice during a chimney fire. You have to understand what is burning before you come up with ideas on how to extinguish it. Just like you can't put a gasoline fire out with water, you can't expect to do the same with a chimney fire. Chimney fires burn at up to 2000 degrees F. and creosote is the combustible product burning. Wet rags or newspaper just don't have the extinguishing power to dowse a 20, 30 or 40' chimney caked with 1/2" of creosote or more throughout the run. Leave the fire fighting to the professionals.
Another bad idea is to discharge a fire extinguisher into your firebox. You might put out the fire in the fire box, but that does not put out the chimney fire. You also run the risk of forcing hot coals into the living space spreading the fire indoors. Call 911 instead!
Chimneys should always be inspected after a chimney fire, especially Class A chimneys. I believe that one manufacturer of Class A states that their insulated chimney can withstand 2000 degrees for 20 minutes. That's something we should all be aware of when your chimney is on fire.
Personally I think an ounce of prevention is worth a pound of cure. I keep my system clean, burn dry seasoned wood, know how much creosote I produce based on my style of burning, and how often to clean my chimney, so I don't need to worry about chimney fires and I can sleep better at night.
Knowledge is power.
Ted
www.woodhomeheating.com