Important Values, Figures, and Thresholds

Question 1

Combustible Gas Detector (CGD) Alarm Threshold

Answer 1

Must alarm when detecting combustible gas concentrations exceeding 10% Lower Explosive Limit (LEL). If measured concentrations exceed 10% LEL, the auditor must inform homeowners, advise evacuation, leave the home, and notify emergency services/fuel providers

Question 2

Ambient Carbon Monoxide (CO) Action Levels

Answer 2

70 ppm or greater: Immediately terminate inspection, notify homeowner/occupant to evacuate building, auditor immediately leaves, notify emergency services from outside.

36 ppm - 69 ppm: Advise homeowner/occupant of elevated levels, open windows/doors, recommend turning off all possible CO sources, and contact a qualified professional if source is a permanently installed appliance.

9 ppm - 35 ppm: Advise CO detected, recommend checking all possible CO sources, opening windows/doors, and contacting a qualified professional if source is a permanently installed appliance.

Question 3

Minimum Required Slope of a Vent Connector (Combustion Appliances)

Answer 3

One-quarter inch per linear foot of positive rise from the appliance to the vertical flue.

Question 4

Minimum Clearance for Water Heaters in a Garage

Answer 4

Must be a minimum of 18 inches above the floor, unless listed as flammable vapor ignition resistant (FVIR)

Question 5

Maximum Allowable BTUh for Unvented Heaters

Answer 5

Overall: Maximum 40,000 BTUh.
In a bedroom: Not more than 10,000 BTUh.
In a bathroom: Not more than 6,000 BTUh

Question 6

CO Thresholds for Fossil Fuel-Fired Combustion Appliances (Air-Free unless noted)

Answer 6

400 ppm air free: Central Furnace, Boiler, Floor Furnace, Gravity Furnace, Wall Furnace (Direct Vent), Clothes Dryer, Gas Log (installed in wood burning fireplace).
200 ppm air free: Wall Furnace (BIV), Vented Room Heater, Unvented Room Heater, Water Heater.
225 ppm as measured: Oven/Broiler.
25 ppm as measured: Refrigerator, Gas Log (gas fireplace)

Question 7

Recommended Minimum R-Value for Duct Insulation

Answer 7

R-8 for ducts in vented attics and other unconditioned zones, including encapsulated attics and semi-conditioned crawl spaces. In humid climate zones, metal cooling system ducts and plenums inside the thermal boundary shall be insulated to R-8 to prevent condensation.

Question 8

Duct Leakage Action Level (Qualitative Testing with Pressure Difference)

Answer 8

If pressure difference exceeds 3 Pa, duct sealing shall be recommended