CCS CCS Fireplace Anatomy & Components 2 — Questions and Answers
Question 1: What is the purpose of the damper in a fireplace?
- To hold the flue liner in position
- To control the flow of air and combustion gases between the firebox and the flue, and to close the flue when the fireplace is not in use (Correct answer)
- To support the smoke shelf
- To direct ash into the ash dump
Correct answer: To control the flow of air and combustion gases between the firebox and the flue, and to close the flue when the fireplace is not in use
The damper regulates airflow during fires and seals the flue when closed to prevent heat loss and animal entry when the fireplace is not being used.
Question 2: A top-sealing damper differs from a traditional throat damper because it:
- Is installed in the smoke chamber instead of the throat
- Mounts at the top of the chimney and seals the entire flue with a rubber gasket when closed (Correct answer)
- Is only used with gas fireplace inserts
- Replaces the smoke shelf in modern fireplace designs
Correct answer: Mounts at the top of the chimney and seals the entire flue with a rubber gasket when closed
Top-sealing dampers install at the top of the flue and seal with a rubber gasket, providing a much better energy seal than traditional throat dampers and also serving as a cap.
Question 3: What is the correct name for the sloped, angled sides of the smoke chamber?
- Corbels or haunches that step the walls inward toward the flue (Correct answer)
- Smoke shelves
- Firebacks
- Firebox jambs
Correct answer: Corbels or haunches that step the walls inward toward the flue
The sloped side walls of the smoke chamber are called corbels or haunches, and NFPA 211 limits the corbel angle to no more than 45 degrees from vertical for proper draft.
Question 4: The firebox opening height-to-width ratio affects draft performance. A generally accepted ratio for proper draft in a standard US masonry fireplace is:
- Opening height should be roughly 2/3 of the opening width (Correct answer)
- Opening height should always equal the opening width
- Opening height must be greater than the width to ensure draft
- The ratio has no effect on draft performance
Correct answer: Opening height should be roughly 2/3 of the opening width
A firebox opening where the height is approximately 2/3 of the width follows traditional proportions that balance combustion air intake with proper draft velocity.
Question 5: Firebrick used in a firebox is different from common brick because it:
- Is larger in size to resist cracking
- Is manufactured to withstand repeated high-temperature cycles without spalling or cracking (Correct answer)
- Contains more lime for flexibility
- Is hollow to reduce heat transfer
Correct answer: Is manufactured to withstand repeated high-temperature cycles without spalling or cracking
Firebrick is made from refractory clay fired at high temperatures to create a dense, heat-resistant material capable of withstanding the thermal cycling inside a firebox.
Question 6: What is refractory mortar (fireclay mortar) and why is it required in firebox construction?
- A standard Type S mortar used for its flexibility in freeze-thaw conditions
- A heat-resistant mortar that can withstand firebox temperatures without cracking or degrading (Correct answer)
- A waterproofing compound applied to the firebox exterior
- A sealant used only on the smoke chamber parging
Correct answer: A heat-resistant mortar that can withstand firebox temperatures without cracking or degrading
Refractory mortar is specifically formulated to tolerate the extreme temperatures inside a firebox without cracking, unlike standard masonry mortars which would fail quickly.
CCS CCS Fireplace Anatomy & Components 2
What is the purpose of the damper in a fireplace?