NFPA 90B Residential Warm Air
Heating Systems Exam With Actual
Questions & Verified Answers,Plus
Rationales/Expert Verified For
Guaranteed Pass /2026 /Latest
Update/Instant Download Pdf
1. What is the primary purpose of NFPA 90B?
A. To regulate industrial furnace design
B. To prevent fire and smoke hazards in residential warm air
heating systems
C. To mandate energy efficiency standards
D. To establish plumbing codes
B. To prevent fire and smoke hazards in residential warm air heating
systems
Rationale: NFPA 90B provides minimum requirements to protect life
and property from fire and smoke hazards in residential warm air
heating and air-conditioning systems.
2. Which type of duct material is generally prohibited in
residential warm air heating systems?
A. Galvanized steel
B. Flexible metal
C. Plastic
D. Aluminum
,C. Plastic
Rationale: NFPA 90B prohibits combustible materials such as plastic
for ducts in residential warm air heating systems because they can
easily ignite.
3. What is the minimum clearance required between a warm air
furnace and combustible materials?
A. 1 inch
B. 3 inches
C. 6 inches
D. As specified by the manufacturer
D. As specified by the manufacturer
Rationale: NFPA 90B requires following the manufacturer’s
installation instructions for clearances to combustibles. If
instructions are not provided, default clearances per the standard
should be used.
4. What is the maximum allowable temperature rise across a
residential warm air furnace?
A. 50°F
B. 90°F
C. 100°F
D. 150°F
B. 90°F
Rationale: NFPA 90B specifies a maximum temperature rise of 90°F
across the furnace to prevent overheating and potential fire
hazards.
5. Residential warm air heating systems must have return air
openings sized to prevent:
A. Excessive noise
B. Air filter replacement
, C. Furnace overheating
D. Duct leakage
C. Furnace overheating
Rationale: Adequate return air ensures the furnace does not
overheat, which could create a fire hazard.
6. What is the required rating for a furnace filter in residential
systems?
A. UL 900
B. ASTM D228
C. ISO 16890
D. None
A. UL 900
Rationale: Filters must comply with UL 900 to ensure they are safe
for use in HVAC systems and do not pose a fire hazard.
7. How must ducts passing through combustible construction be
protected?
A. With asbestos wrapping
B. With sheet metal sleeve or equivalent
C. No protection is needed
D. With fiberglass insulation only
B. With sheet metal sleeve or equivalent
Rationale: NFPA 90B requires that ducts passing through
combustible materials be enclosed in a noncombustible sleeve to
prevent fire spread.
8. What is the maximum distance a single furnace duct can extend
without a smoke detector in the duct?
A. 10 feet
B. 25 feet
, C. 50 feet
D. NFPA 90B does not require duct smoke detectors in
residential systems
D. NFPA 90B does not require duct smoke detectors in residential
systems
Rationale: Duct smoke detectors are typically required in
commercial applications (NFPA 90A); NFPA 90B focuses on
residential systems and does not mandate them.
9. What is the minimum return air area required for a residential
furnace?
A. 1 square inch per 1000 BTU/hr
B. 1 square inch per 400 BTU/hr
C. 1 square inch per 100 BTU/hr
D. 1 square inch per 500 BTU/hr
B. 1 square inch per 400 BTU/hr
Rationale: NFPA 90B requires return air openings to prevent
overheating and maintain proper airflow. The sizing ratio is
generally 1 in² per 400 BTU/hr.
10. What is the maximum allowable pressure in a residential
warm air duct system?
A. 1 inch water gauge
B. 2 inches water gauge
C. 0.5 inch water gauge
D. 3 inches water gauge
C. 0.5 inch water gauge
Rationale: NFPA 90B recommends a maximum pressure of 0.5 inch
WG to prevent duct leakage and maintain safety.
Heating Systems Exam With Actual
Questions & Verified Answers,Plus
Rationales/Expert Verified For
Guaranteed Pass /2026 /Latest
Update/Instant Download Pdf
1. What is the primary purpose of NFPA 90B?
A. To regulate industrial furnace design
B. To prevent fire and smoke hazards in residential warm air
heating systems
C. To mandate energy efficiency standards
D. To establish plumbing codes
B. To prevent fire and smoke hazards in residential warm air heating
systems
Rationale: NFPA 90B provides minimum requirements to protect life
and property from fire and smoke hazards in residential warm air
heating and air-conditioning systems.
2. Which type of duct material is generally prohibited in
residential warm air heating systems?
A. Galvanized steel
B. Flexible metal
C. Plastic
D. Aluminum
,C. Plastic
Rationale: NFPA 90B prohibits combustible materials such as plastic
for ducts in residential warm air heating systems because they can
easily ignite.
3. What is the minimum clearance required between a warm air
furnace and combustible materials?
A. 1 inch
B. 3 inches
C. 6 inches
D. As specified by the manufacturer
D. As specified by the manufacturer
Rationale: NFPA 90B requires following the manufacturer’s
installation instructions for clearances to combustibles. If
instructions are not provided, default clearances per the standard
should be used.
4. What is the maximum allowable temperature rise across a
residential warm air furnace?
A. 50°F
B. 90°F
C. 100°F
D. 150°F
B. 90°F
Rationale: NFPA 90B specifies a maximum temperature rise of 90°F
across the furnace to prevent overheating and potential fire
hazards.
5. Residential warm air heating systems must have return air
openings sized to prevent:
A. Excessive noise
B. Air filter replacement
, C. Furnace overheating
D. Duct leakage
C. Furnace overheating
Rationale: Adequate return air ensures the furnace does not
overheat, which could create a fire hazard.
6. What is the required rating for a furnace filter in residential
systems?
A. UL 900
B. ASTM D228
C. ISO 16890
D. None
A. UL 900
Rationale: Filters must comply with UL 900 to ensure they are safe
for use in HVAC systems and do not pose a fire hazard.
7. How must ducts passing through combustible construction be
protected?
A. With asbestos wrapping
B. With sheet metal sleeve or equivalent
C. No protection is needed
D. With fiberglass insulation only
B. With sheet metal sleeve or equivalent
Rationale: NFPA 90B requires that ducts passing through
combustible materials be enclosed in a noncombustible sleeve to
prevent fire spread.
8. What is the maximum distance a single furnace duct can extend
without a smoke detector in the duct?
A. 10 feet
B. 25 feet
, C. 50 feet
D. NFPA 90B does not require duct smoke detectors in
residential systems
D. NFPA 90B does not require duct smoke detectors in residential
systems
Rationale: Duct smoke detectors are typically required in
commercial applications (NFPA 90A); NFPA 90B focuses on
residential systems and does not mandate them.
9. What is the minimum return air area required for a residential
furnace?
A. 1 square inch per 1000 BTU/hr
B. 1 square inch per 400 BTU/hr
C. 1 square inch per 100 BTU/hr
D. 1 square inch per 500 BTU/hr
B. 1 square inch per 400 BTU/hr
Rationale: NFPA 90B requires return air openings to prevent
overheating and maintain proper airflow. The sizing ratio is
generally 1 in² per 400 BTU/hr.
10. What is the maximum allowable pressure in a residential
warm air duct system?
A. 1 inch water gauge
B. 2 inches water gauge
C. 0.5 inch water gauge
D. 3 inches water gauge
C. 0.5 inch water gauge
Rationale: NFPA 90B recommends a maximum pressure of 0.5 inch
WG to prevent duct leakage and maintain safety.
