Combustion Safety Principles Flashcards
7 cards from real HERS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Combustion Safety Principles flashcards as text
The spillage test for a naturally vented water heater is typically performed by holding a smoke pencil or mirror near the draft hood opening. A passing result shows:
Answer: Smoke drawn into the draft hood and up the flue
Smoke drawn into the draft hood indicates proper upward draft pulling combustion gases safely out of the home.
What is the typical worst-case depressurization threshold (in Pascals) at which natural-draft combustion appliances are considered at high risk for sustained backdrafting?
Answer: -5 Pa
A CAZ pressure at or below -5 Pa relative to outside under worst-case conditions indicates high backdrafting risk for naturally vented appliances.
Which fuel produces carbon monoxide when burned with insufficient oxygen?
Answer: Any carbon-containing fuel
Any fuel containing carbon—natural gas, propane, oil, wood, coal—can produce CO when combustion is incomplete due to insufficient oxygen.
A combustion safety inspection reveals an improper connector material: single-wall black iron pipe passing through a bedroom wall to the chimney. The correct action is:
Answer: Flag it as a hazard—single-wall connectors must not pass through living spaces
Single-wall flue connectors are not permitted to pass through or be concealed in walls, floors, or ceilings due to CO leak and fire risk.
During a combustion safety test, which appliance configuration typically creates the greatest depressurization of the combustion appliance zone?
Answer: A large central-return air handler drawing air from the CAZ
An air handler with a return located in the CAZ can draw large volumes of air from that zone, dramatically depressurizing it and inducing backdrafting in co-located appliances.
What is the purpose of a draft diverter (draft hood) on an atmospheric water heater?
Answer: To dilute flue gases with room air and protect the burner from downdrafts
The draft hood mixes room air with flue gases to moderate temperature and prevents downdrafts from extinguishing the pilot or burner.
Which metric best indicates the efficiency and completeness of combustion in a gas appliance flue analysis?
Answer: CO-to-CO2 ratio in the flue gases
The CO-to-CO2 ratio reveals how much carbon burned completely (CO2) versus incompletely (CO), giving a direct measure of combustion quality.