Thanks for the heads-up on ordering from Rutland, as of today (12/10) they are still selling them for $8.00/each plus shipping (dependent upon location), so 2 are on the way.
I stumbled onto the product a year ago or so at a Menard's in Ohio (no longer listed on their site) and bought one "as a safety precaution"...
A few months later I made the mistake (among others, I suppose) of using too many small twigs and stuff from outside at once and the flames reached much higher than usual, and then I heard and felt a rumble like thunder, but it wasn't... I ran outside briefly to see a glow and sparks from the chimney, ran back in and lit and threw in the Chimfex flair and closed the glass doors and called 911 (in some order). Actually a fire house is only 1 block away, but by the time they got here the roar had already subsided and little was coming out of the chimney. They put a little water on the fire in the grate and went up the floors along the chimney route with an infrared detector to see if there were any hot spots (none).
I saw on one web site for firefighters and such that they had confidence in the product, though they say they prefer plastic bags filled with dry fire retardant that they get by the drum as firefighters ("No, never use water unless you want to cause structural damage by the rapid temperature shock").
As far as how they work, some combination of using up the oxygen and altering the creosote from the flammable greasy stuff to a not-very flammable powder- I couldn't figure out anything more exact from what I could find on the web. I did find some nice study results on decrease in flue temps, etc.
I have no idea (and could find no info with a little searching) on how the differing products compare.
BTW, I have a traditional fire place in a 100+ year old house with glass doors and a "heat grate" (hollow steel tubes as a grate with fan blown air) to get more efficiency than the typical fire place. I once made a rough design of a curved chimney throat out of aluminum as in a "Rumford" fire place and did find much better flow of smoke up the chimney instead of into the room...if I had the skill, materials, and knowledge how to retrofit it with with something more permanent I would love too, so if anyone has done this I would be quite greatful to hear about it. The cost of doing a rebuild or a good insert is a bit much, considering all of the other things "this old house" needs.
