A chimney may not seem like a safety hazard, and properly designed, it doesn't need to be. Here are some things to consider as you select your chimney not only for style but for safety as well.
In the 1800s, massive chimneys with thick walls were effective in preventing chimney fires. So-called "barrel chimneys" had several flues and were integrated into masonry walls to provide protection. Since the framing was not combustible, the danger of fire was significantly reduced. Most homes today are not made of masonry. They are wood frame houses, and the barrel chimney does not provide the hoped-for protection.
A hundred years ago, chimneys for log cabins were designed at an angle and held up by wooden supports. This seems ungainly to us today, but there was a definite safety purpose in mind. The mud and wattle chimneys were prone to catching fire from the inside. When this happened, the homeowner would kick out the supports for the chimney, allowing it to topple and burn safely alongside the house rather than into it.
Other strategies used involved separating the chimney from the roof or putting ladders on the roof so that the fire could be put out easily from above. All this is probably much more work than the modern homeowner has time to contemplate. And the look is often something that the modern homeowners' association wouldn't care for either.
With today's wood-framed houses and more detailed building codes, other fire prevention strategies need to be pursued.
The answer is air space. Masonry chimneys get hot. Wood framing should not be placed near them. And insulation should be given space as well. The chimney should be supported within the framing of the house by non-combustible materials such as metal or masonry. Care should be taken to make sure that these materials do not themselves become too hot and turn into fire hazards.
To avoid fireplace hazard, combustible materials should have a clearance of at least 2 inches from the front faces and sides of a masonry fireplace. The clearance should be at least 4 inches from the back. In front, combustible materials must be placed at least 6 inches from the fireplace opening. And if those materials are within 12 inches, they should not project more than 1/8 inch for every inch of distance from the opening. The air space should not be filled except for fire blocking.
Exceptions can be made to this rule for a masonry fireplace that is listed and labeled as safe for contact with combustible materials.
Combustible materials such as wood-siding, framing, trim, and flooring may be placed around the sides and hearth extensions, but not the back, of masonry fireplaces. These materials must be at least 12 inches from the inside surface of the firebox.
Lastly, every space between the fireplace and floor or ceiling should be thoroughly fire blocked using non-combustible material that is securely fastened. This should be done to a depth of 1 inch between wood joists, headers, or beams and placed on strips of metal or metal lath between the chimney and the combustible material.