NFI gas exam reference questions and
answers with solutions
COAXIAL DIRECT VENT
- A smaller pipe that is fixed with spacers inside a larger outer pipe removes combustion by
products while the space between the two pipes introduced combustion air to the appliance
coaxial pipes may be rigid or flexible.
COLLINEAR DIRECT VENT
- Two separate pipes, one for combustion air intake and the other for combustion by products
discharge.
- The pipes are typically flexible pipes.
- Clearances for coaxial and collinear systems may vary.
FIRE STOP SPACER
- The fire stop provides lateral support for the vent, maintains clearance for the penetration of
floors/ceilings, and prevents unwanted communication and airflow between building levels. -
Fire stops may also be required for through the wall installations.
- A fire stop may be required on both sides of the wall period the first stop may include a shield
that must be positioned at the top of the opening.
VENT TERMINATION MUST BE HOW FAR ABOVE GRADE?
12" at least
DIRECT VENT
- A combustion appliance that draws combustion air from outdoors and has a sealed exhaust
system.
- Exhaust byproducts are expelled outside as well.
HOW IS THE PILOT FLAME USUALLY ADJUSTED?
By turning the pilot adjustment screw
WHAT MEASURES GAS PRESSURE OUTPUT OF LP/NG?
Manometer
MULTIMETER MEASURES
answers with solutions
COAXIAL DIRECT VENT
- A smaller pipe that is fixed with spacers inside a larger outer pipe removes combustion by
products while the space between the two pipes introduced combustion air to the appliance
coaxial pipes may be rigid or flexible.
COLLINEAR DIRECT VENT
- Two separate pipes, one for combustion air intake and the other for combustion by products
discharge.
- The pipes are typically flexible pipes.
- Clearances for coaxial and collinear systems may vary.
FIRE STOP SPACER
- The fire stop provides lateral support for the vent, maintains clearance for the penetration of
floors/ceilings, and prevents unwanted communication and airflow between building levels. -
Fire stops may also be required for through the wall installations.
- A fire stop may be required on both sides of the wall period the first stop may include a shield
that must be positioned at the top of the opening.
VENT TERMINATION MUST BE HOW FAR ABOVE GRADE?
12" at least
DIRECT VENT
- A combustion appliance that draws combustion air from outdoors and has a sealed exhaust
system.
- Exhaust byproducts are expelled outside as well.
HOW IS THE PILOT FLAME USUALLY ADJUSTED?
By turning the pilot adjustment screw
WHAT MEASURES GAS PRESSURE OUTPUT OF LP/NG?
Manometer
MULTIMETER MEASURES
