Combustion Safety Principles Flashcards
6 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 6 Combustion Safety Principles flashcards as text
A HERS Rater is performing a worst-case depressurization test in a Combustion Appliance Zone (CAZ). After establishing a baseline pressure, which of the following steps should be performed FIRST to create the worst-case scenario?
Answer: Close all exterior doors and windows.
To create a worst-case depressurization scenario, the house must first be isolated from the outdoors. This is achieved by closing all exterior doors and windows, which is a foundational step before activating any exhaust appliances that would depressurize the house.
During a combustion safety inspection, a HERS Rater measures an ambient carbon monoxide (CO) level of 40 ppm in the home. According to RESNET and BPI standards, what is the immediate required action?
Answer: Advise the homeowner to open windows and doors and to contact a qualified professional.
According to combustion safety standards, if ambient CO levels exceed 35 ppm, the test must be stopped. The rater should advise the homeowner of the elevated levels, recommend ventilating the house by opening windows and doors, and advise them to have the potential source (the appliance) checked by a qualified professional. Evacuation is typically required at higher levels (e.g., 70 ppm or greater).
Which of the following conditions is most likely to cause backdrafting of a natural draft water heater?
Answer: Operation of a powerful, uncompensated kitchen exhaust fan.
Powerful exhaust fans can create significant negative pressure within a home. If there is not adequate makeup air, this depressurization can overcome the natural buoyancy of the flue gases in an atmospheric appliance, pulling them back into the living space.
When performing a spillage test on a natural draft gas furnace that has been off and has a cold vent, at what point during the main burner operation should spillage be assessed?
Answer: At 5 minutes.
For a natural draft appliance with a cold vent, it takes time for the flue to warm up and establish a proper draft. Standard protocols, such as those from BPI, require checking for spillage at 5 minutes of main burner operation to allow sufficient time for the draft to establish. Checking earlier may result in a false failure.
A homeowner has recently air-sealed their attic and crawlspace. What is the primary combustion safety concern a HERS Rater should investigate related to this work?
Answer: Reduced dilution of potential CO spillage and increased depressurization.
Making a house tighter reduces the amount of natural air infiltration. This has two major impacts on combustion safety: 1) it makes the house more susceptible to depressurization from exhaust fans, increasing backdrafting risk, and 2) if spillage does occur, the reduced air exchange rate means the harmful gases, like CO, will not be diluted as quickly, leading to higher concentrations.
According to RESNET Standard Chapter 8, which of these tests is a required part of a combustion safety inspection?
Answer: Gas leakage test on all appliance fittings and connections.
RESNET Standard Chapter 8 specifically requires protocols for Carbon Monoxide (CO) testing and Depressurization testing. A critical part of the overall safety check, as outlined in section 802.3, is to perform a gas leakage test on the fittings and connections of gas appliances within the home to identify any potentially hazardous leaks.