Wanted to add after seeing one star review that creosote was running down chimney after burning four bricks. This stuff is really dry (8 percent moisture content per brick) so a stove top thermometer is a must to prevent over firing your stove. I am currently mixing two bricks in with some semi seasoned wood to balance out the overall moisture content in the firebox. If cordwood is not available fewer bricks at a time or dampening down the draft a little more than normal may be required. It sounds like the chimney needed to be cleaned. There's no way four pieces of any type of wood even green wood would produce so much creosote.

I have been using these, along with regular firewood, in my outdoor furnace and my fireplace over the last 3 years. I use 2-3 pallets of these per year. Packaging: They are shrink-wrapped, but some of the packs are not totally sealed. They MUST be kept in a dry area, or they will absorb moisture and expand and crumble. They also leave substantial dust, once unwrapped. This isn't a problem if used outdoors, but will leave dust and small crumbs on the floor indoors. My solution is to stack several, unopened packs on a log rack by the fireplace. To use them, I slice open the top of the shrink-wrap and remove fire-blocks as needed. I then carefully empty the shrink-wrap into the fireplace, roll it up to prevent any residue from spilling out, and discard it in the trash. As the product description states, a pallet of these fire blocks is equivalent to at least 1.5 cords of firewood. They are cleaner than storing firewood, with no bark, dirt or bugs. They burn hot and cleaner and longer than the equivalent weight of firewood, and they leave much less ash, and don't cause creosote buildup. As the instructions state, they are best started in an already-existing fire. They do not burn easily if started by themselves. If they are used in a wood stove, start off by using just one. They burn hot and the stove can be damaged if it gets too hot. When using in a fireplace or outdoor furnace, make sure there is a small space between them to help them burn, or break them into 2 or 3 pieces before placing them.