Core TradesQuestion 95 of 700
A gas furnace is installed in a small, tightly sealed closet with no combustion air openings. The MOST likely dangerous consequence is:
a.The furnace runs more efficiently
b.Incomplete combustion and possible carbon monoxide production due to insufficient combustion air
c.The furnace produces more heat
d.The gas line will freeze
Explanation
A fuel-burning appliance needs adequate combustion air; a sealed closet starves the burner, causing incomplete combustion, potential backdrafting, and carbon monoxide. It does not improve efficiency or heat output, and lack of combustion air does not freeze the gas line.
Law Reference: 2025 CA Mechanical CodePractice all 700 questions free — no signup required.
Related questions on this topic
- A contractor plans to join copper tubing to galvanized steel pipe directly. The BEST practice to avoid a common failure is to:
- CALCULATION: A vertical drainage stack must accommodate horizontal branch offsets. A trap arm for a 2-inch fixture drain is allowed a maximum developed length. If the code table permits 8 feet for a 2-inch trap arm, and the layout requires 11 feet to the vent, the installer should:
- A vent terminating through the roof must extend a minimum height above the roof and be set back from any vertical surface or opening, MAINLY to:
- CALCULATION: A common rule of thumb provides 1 square inch of combustion air opening per 1,000 Btu/h of appliance input when air comes from inside a large space. For a 100,000 Btu/h furnace using two openings (high and low), what free area does EACH opening need under this rule?
- A large commercial kitchen exhaust hood removes a high volume of air. Without makeup air, the space goes into strong negative pressure. The BEST solution is to:
- During a split-system AC installation, the refrigerant line set is run with several tight kinks and an excessively long distance beyond the manufacturer's limit. The MOST likely result is:
Last reviewed: · editorial process
PrepPass Editorial Team · Verified against California CSLB General Building (B) Trade Examination · How we review