CCS CCS Hearth & Firebox Components 2 — Questions and Answers
Question 1: What is the smoke chamber and what is its primary purpose?
- The finished room where the fireplace is located
- The tapered space above the smoke shelf that compresses smoke before it enters the flue (Correct answer)
- The sealed combustion chamber of a factory-built fireplace
- The area between the damper and the firebox floor
Correct answer: The tapered space above the smoke shelf that compresses smoke before it enters the flue
The smoke chamber is the inverted funnel-shaped space above the smoke shelf that compresses and accelerates combustion gases before they enter the narrow flue.
Question 2: According to CSIA standards, smoke chamber walls should be pargetted for what reason?
- To improve the aesthetic appearance of the chamber
- To smooth the corbeled or stepped masonry surfaces and improve gas flow dynamics (Correct answer)
- To provide an additional fire-resistant barrier
- To seal out radon gas infiltration
Correct answer: To smooth the corbeled or stepped masonry surfaces and improve gas flow dynamics
Parge coating smooths out the rough corbeled brickwork in the smoke chamber, reducing turbulence in rising gases and improving overall draft efficiency.
Question 3: What condition in a smoke chamber is considered a Level 2 inspection finding requiring repair?
- Visible soot staining on chamber walls
- Missing or deteriorated parge coat with gaps exposing masonry joints to flue gases (Correct answer)
- Chamber walls darker than the flue liner above
- A slight forward pitch of the chamber front wall
Correct answer: Missing or deteriorated parge coat with gaps exposing masonry joints to flue gases
Deteriorated parge coat exposing mortar joints allows hot flue gases to contact combustible framing through gaps, creating a fire hazard requiring immediate correction.
Question 4: What is the ideal ratio of flue size to firebox opening area for proper draft performance?
- Flue should equal 100% of the firebox opening
- Flue cross-section should be approximately 1/10 to 1/12 of the firebox opening area (Correct answer)
- Flue should be exactly twice the firebox opening
- No specific ratio is required by code
Correct answer: Flue cross-section should be approximately 1/10 to 1/12 of the firebox opening area
A flue cross-section of 1/10 to 1/12 of the firebox opening area ensures adequate draft velocity without drawing excessive amounts of room air.
Question 5: What is the throat of a fireplace and where is it located?
- The ash pit door in the firebox floor
- The narrow opening between the top of the firebox and the smoke shelf/chamber (Correct answer)
- The front opening of the firebox measured at the hearth
- The connection point between the chimney and the roofline
Correct answer: The narrow opening between the top of the firebox and the smoke shelf/chamber
The throat is the constricted opening at the very top of the firebox where the damper plate sits, connecting the combustion zone to the smoke shelf and chamber above.
Question 6: A smoke chamber that is corbeled outward instead of parged smooth creates what drafting problem?
- It reduces the effective flue liner diameter
- It creates turbulence and eddy currents that can cause smoke to spill back into the room (Correct answer)
- It prevents the damper from closing fully
- It allows carbon monoxide to accumulate in the firebox
Correct answer: It creates turbulence and eddy currents that can cause smoke to spill back into the room
Rough, stepped corbeled walls in the smoke chamber cause turbulence in rising smoke that disrupts laminar flow, increasing the risk of smoke rollout into the living space.
CCS CCS Hearth & Firebox Components 2
What is the smoke chamber and what is its primary purpose?