Missouri (St. Louis County) Commercial HVAC
Servicer/Installer - 588-MO-SL Contractor
Practice Exam -Questions with Correct Answers
and Explanations.
1. Which agency issues the Mechanical Contractor License in St. Louis County?
A) Missouri Department of Labor
B) St. Louis County Department of Public Works
C) Board of Mechanical Examiners
D) OSHA
Correct Answer: C
Explanation: The Board of Mechanical Examiners reviews applications and issues the
license, while the Department of Public Works enforces compliance .
2. How many hours of continuing education are required every two years to maintain a
St. Louis County mechanical contractor license?
A) 8
B) 12
C) 16
D) 24
Correct Answer: B
Explanation: County ordinance mandates 12 hours of approved continuing education for
license renewal .
3. Which document must be submitted with a permit application for a new commercial
HVAC installation?
A) Contractor's liability insurance certificate
B) OSHA 10-hour card
,C) Manufacturer's warranty
D) Energy Star rating report
Correct Answer: A
Explanation: Proof of liability insurance is required to demonstrate financial responsibility
before a permit is issued .
4. Performing HVAC work without a permit in St. Louis County is classified as a:
A) Civil infraction
B) Misdemeanor
C) Felony
Explanation: The county treats unpermitted work as a misdemeanor, subject to fines and
possible license suspension .
5. Under the International Mechanical Code, Section M-5 in St. Louis County modifies
which requirement?
A) Minimum duct insulation R-value
B) Outdoor air intake clearance distances
C) Maximum refrigerant charge per system
D) Fire damper testing frequency
Correct Answer: B
*Explanation: Section M-5 modifies outdoor air intake clearance distances specific to St.
Louis County requirements .*
6. Which law governs the licensing requirements for HVAC servicers in St. Louis County?
A) Missouri State Licensing Law
B) Local Licensing Law for St. Louis County
C) International Mechanical Code
D) Federal HVAC Licensing Act
Correct Answer: B
,Explanation: The local licensing requirements for HVAC servicers in St. Louis County are
governed by the Local Licensing Law specific to that jurisdiction .
7. What is a key amendment to the International Mechanical Code as it applies locally in
St. Louis County?
A) Increased minimum duct insulation R-values
B) Specific licensing procedures for HVAC installers
C) Exemption of residential systems from licensing
D) No amendments have been made
Correct Answer: B
Explanation: The local amendments often include specific licensing procedures to ensure
compliance with regional regulations and safety standards .
8. A backdraft damper is required when a commercial exhaust system is located within
how many feet of a building's intake?
A) 4 ft
B) 8 ft
C) 12 ft
D) 20 ft
Correct Answer: B
*Explanation: An 8-foot separation triggers the need for a backdraft damper to prevent
exhaust gases from re-entering the intake .*
9. The fire-damper rating required for a duct passing through a rated fire wall in a
commercial building is:
A) 1-hour UL 555
B) 2-hour UL 555
C) 3-hour NFPA 252
D) 4-hour ASTM E
Correct Answer: B
*Explanation: A 2-hour UL 555 fire-damper is the minimum for ducts penetrating fire-
rated walls in most commercial settings .*
, 10. Which local regulation affects venting requirements for gas appliances in St. Louis
County?
A) International Fuel Gas Code amendments
B) National Electrical Code
C) OSHA ventilation standards
D) EPA emissions standards
Correct Answer: A
Explanation: The International Fuel Gas Code, with local amendments, governs venting
requirements for gas appliances .
11. The 2024 IMC Update course approved by the St. Louis Board of Examiners for
Mechanical Licensing covers all of the following EXCEPT:
A) Chapter 4: Ventilation
B) Chapter 5: Exhaust Systems
C) Chapter 11: Refrigeration
D) Chapter 15: Electrical Wiring Methods
Correct Answer: D
*Explanation: The 2024 IMC Update covers Chapters 1-11, including Ventilation, Exhaust
Systems, and Refrigeration, but not Chapter 15 (Electrical Wiring Methods), which is
covered by the NEC .*
12. Under IMC Chapter 3, what is required for condensate disposal?
A) Discharge directly to roof
B) Discharge to a sanitary sewer or outside grade via approved method
C) Discharge to storm drain
D) No disposal required
Correct Answer: B
Explanation: IMC Section 307 requires condensate disposal to a sanitary sewer or outside
grade through an approved method to prevent damage and health hazards .
13. According to IMC Chapter 5, commercial kitchen makeup air systems must be
interlocked with:
Servicer/Installer - 588-MO-SL Contractor
Practice Exam -Questions with Correct Answers
and Explanations.
1. Which agency issues the Mechanical Contractor License in St. Louis County?
A) Missouri Department of Labor
B) St. Louis County Department of Public Works
C) Board of Mechanical Examiners
D) OSHA
Correct Answer: C
Explanation: The Board of Mechanical Examiners reviews applications and issues the
license, while the Department of Public Works enforces compliance .
2. How many hours of continuing education are required every two years to maintain a
St. Louis County mechanical contractor license?
A) 8
B) 12
C) 16
D) 24
Correct Answer: B
Explanation: County ordinance mandates 12 hours of approved continuing education for
license renewal .
3. Which document must be submitted with a permit application for a new commercial
HVAC installation?
A) Contractor's liability insurance certificate
B) OSHA 10-hour card
,C) Manufacturer's warranty
D) Energy Star rating report
Correct Answer: A
Explanation: Proof of liability insurance is required to demonstrate financial responsibility
before a permit is issued .
4. Performing HVAC work without a permit in St. Louis County is classified as a:
A) Civil infraction
B) Misdemeanor
C) Felony
Explanation: The county treats unpermitted work as a misdemeanor, subject to fines and
possible license suspension .
5. Under the International Mechanical Code, Section M-5 in St. Louis County modifies
which requirement?
A) Minimum duct insulation R-value
B) Outdoor air intake clearance distances
C) Maximum refrigerant charge per system
D) Fire damper testing frequency
Correct Answer: B
*Explanation: Section M-5 modifies outdoor air intake clearance distances specific to St.
Louis County requirements .*
6. Which law governs the licensing requirements for HVAC servicers in St. Louis County?
A) Missouri State Licensing Law
B) Local Licensing Law for St. Louis County
C) International Mechanical Code
D) Federal HVAC Licensing Act
Correct Answer: B
,Explanation: The local licensing requirements for HVAC servicers in St. Louis County are
governed by the Local Licensing Law specific to that jurisdiction .
7. What is a key amendment to the International Mechanical Code as it applies locally in
St. Louis County?
A) Increased minimum duct insulation R-values
B) Specific licensing procedures for HVAC installers
C) Exemption of residential systems from licensing
D) No amendments have been made
Correct Answer: B
Explanation: The local amendments often include specific licensing procedures to ensure
compliance with regional regulations and safety standards .
8. A backdraft damper is required when a commercial exhaust system is located within
how many feet of a building's intake?
A) 4 ft
B) 8 ft
C) 12 ft
D) 20 ft
Correct Answer: B
*Explanation: An 8-foot separation triggers the need for a backdraft damper to prevent
exhaust gases from re-entering the intake .*
9. The fire-damper rating required for a duct passing through a rated fire wall in a
commercial building is:
A) 1-hour UL 555
B) 2-hour UL 555
C) 3-hour NFPA 252
D) 4-hour ASTM E
Correct Answer: B
*Explanation: A 2-hour UL 555 fire-damper is the minimum for ducts penetrating fire-
rated walls in most commercial settings .*
, 10. Which local regulation affects venting requirements for gas appliances in St. Louis
County?
A) International Fuel Gas Code amendments
B) National Electrical Code
C) OSHA ventilation standards
D) EPA emissions standards
Correct Answer: A
Explanation: The International Fuel Gas Code, with local amendments, governs venting
requirements for gas appliances .
11. The 2024 IMC Update course approved by the St. Louis Board of Examiners for
Mechanical Licensing covers all of the following EXCEPT:
A) Chapter 4: Ventilation
B) Chapter 5: Exhaust Systems
C) Chapter 11: Refrigeration
D) Chapter 15: Electrical Wiring Methods
Correct Answer: D
*Explanation: The 2024 IMC Update covers Chapters 1-11, including Ventilation, Exhaust
Systems, and Refrigeration, but not Chapter 15 (Electrical Wiring Methods), which is
covered by the NEC .*
12. Under IMC Chapter 3, what is required for condensate disposal?
A) Discharge directly to roof
B) Discharge to a sanitary sewer or outside grade via approved method
C) Discharge to storm drain
D) No disposal required
Correct Answer: B
Explanation: IMC Section 307 requires condensate disposal to a sanitary sewer or outside
grade through an approved method to prevent damage and health hazards .
13. According to IMC Chapter 5, commercial kitchen makeup air systems must be
interlocked with:
