See Part 1 here.
Some woods produce potentially dangerous combustion products when burned, that can pose a real hazard through smoke inhalation. Sumac and mountain laurel are often warned against to those planning on a backcountry camping trip for use in a cookfire, as the toxins in their smoke are said to contaminate food. Likewise for mangrove wood.
Staghorn Sumac.
The toxin found in rhododendrons and mountain laurel is called grayanotoxin, which can be fatal if inhaled in its pure form. However, grayanotoxin is destroyed above 150 degrees Celsius, making this more of an old wives tale. Many people burn this wood with no ill effect, and Scotland even encourages its citizens to burn rhododendrons as they are invasive there.
Mountain Laurel.
Oleander shrubs are also quite toxic, and should not even be used to toast marshmallows on, but as they only grow in warmer climates with no frost, incidents are rare. In addition, be sure not to burn any wood that had poison ivy or poison oak growing on it, as burning can release an irritant oil called urushiol into the smoke.
Oleander.
Lastly, never burn treated lumber scraps. The EPA lists treated wood as hazardous waste, and with good reason. It is full of arsenic and other toxins that are not destroyed by incineration. Arsenic is no joke- a family that used wood treated with chromium-copper-arsenate in their wood stove has serious issues from breathing arsenic dust all winter. They suffered severe nosebleeds, extreme headaches and rapid hair loss. The kids were getting seizures and the adults complained of blackouts and confusion.
