Jack Pixley's Homeowner's Guide

Smoke Chamber Design

Improper smoke chamber design is a major cause of smoking fireplaces.

Smoke Chambers

The National Fire Protection Association (NFPA 211) code standard requires:

  • Smoke chambers lined with firebrick must be at least 6” thick (if unlined…8” thick).
  • Smoke chamber height shall not be greater than the inside width of the fireplace opening.
  • Smoke chamber depth shall not be greater than the depth of the fireplace firebox.
  • Inner surfaces of the smoke chamber shall be smooth and not inclined more than 45 degrees from vertical.
Note:  Corbelling is not permitted unless covered with appropriate material. A rough surface will result in turbulence, which causes resistance to proper flow.

Potential Problems

  • Smoke chamber walls of inadequate thickness may pose a fire safety hazard (impossible to discover without an NFPA 211 – Level III inspection @ making holes).
  • Smoke chamber clearance to combustibles, if less than the required 2 inches, will pose a serious fire hazard (again, this is impossible to discover without a Level III inspection).
  • Rough inner surfaces will result in turbulence, which causes resistance to proper flow.
  • Holes, cracks, corners, and improper interior angles and shape will result in poor performance and creosote buildup.
  • Smoking problems.
  • Inability to inspect and clean properly.

Solutions and Benefits

Chamber Tech 2000 (UL-Listed) can be applied to the inner surface of the smoke chamber. This product will make the surface smooth, therefore reducing resistance to flow. In addition, if installed per the manufacturer’s instructions, it will significantly insulate the smoke chamber making this portion of the fireplace safer.