Fireplace. Unseasoned wood. Creosote.
Make sure that every member of the family knows the rules of fireplace use. They should be aware that no items, other than seasoned wood, should be discarded into the fire. Far too many homeowners think that the fireplace is a miniature incinerator. Below a a short list of materials NOT to burn in your fireplace. Some of the materials contain or emit highly toxic chemicals, or accelerate the build-up of creosote, or are corrosive, or produce high levels of carbon monoxide.

UNSEASONED WOOD
Do not use wood that has just been cut down. Moisture levels are high in freshly cut wood. This unseasoned wood produces a lot of smoke which in turn will produce above normal levels of creosote. Use only seasoned wood from a reputable source. If in doubt about the age of the firewood let it dry out for a year and use it for the next heating season.

SYNTHETIC LOGS
Personally I would stay away from synthetic logs. Some brands may burn uneven and produce higher levels of carbon monoxide. If you do use them, carefully read all the directions printed on the packaging.

PRESSURE TREATED ("WOLMANIZED") WOOD
Do not use PT wood. You may be tempted to use it seeing all the scrap leftover pieces from building a fence or deck. PT lumber contains arsenic and chromium which are highly toxic.

CEDAR SHINGLES OR SHAKES
If you are installing a new cedar shingle or shake roof do not burn the old shingles or shakes. They may look like perfect kindling wood but the danger is in what you do not see, they are chemically treated.

ENGINEERED WOOD
When repairing or renovating your home do not burn any scrap pieces of engineered wood in the fireplace. These products contain glue, hardeners, resins and other additives which are harmful for the environment. Do not burn: Plywood, particle board, Medium Density Fiberboard (MDF) or Orientated Strand Board (OSB).

HOUSEHOLD TRASH
Household trash contains many toxic chemicals while most paper products produce unwanted creosote build-up. Do not burn: Egg cartons, or glossy paper magazines. Do not burn disposable cups, plates or Styrofoam packaging materials; they will turn into tar-like blobs.

MORE FIREPLACE INFORMATION
WETT and CSIA certified fireplace inspections
Creosote, safe disposal of ashes, child guard shields
Six ways to cure a smoky fireplace

TIPS ON STARTING A FIRE
Warm the chimney by igniting some crumpled newspaper placed at the damper level, to induce an up-draft.
Start the fire small. Fires started too quickly can spill combustion by-products into the room. Use small amounts of tinder at the back of the hearth until the chimney is well heated.
Never operate exhaust fans or central vacuum cleaner when using the fireplace.