CNG - Compressed Natural Gas Facility and Ventilation Requirements Questions and Answers

Question 1

A maintenance garage that services CNG vehicles is located in a cold climate.
The manager needs to install a new heating system.
According to NFPA 52, which of the following heating systems is prohibited from being installed directly within the service bay?

Accepted Answer

A direct-fired combustion air heater located below the ceiling.

Answer

A steam or hot water system with pipes located 8 feet above the floor.

Answer

A radiant tube heater with sealed combustion chambers and external air intake.

Answer

An indirect-fired heater with the burner and ignition source located in a separate room.

Question 2

A facility is being upgraded to a major repair garage for CNG vehicles. Which statement correctly describes the requirements for the mechanical ventilation system's exhaust air intakes per NFPA 52?

Accepted Answer

They must be located at the highest practical point, within 12 inches of the ceiling.

Answer

They must be located within 12 inches of the floor to capture heavier-than-air gases.

Answer

They should be distributed evenly along the walls, approximately 4 feet from the floor.

Answer

They must be positioned directly above each vehicle service bay door.

Question 3

A facility that performs minor maintenance on CNG vehicles, such as oil changes and tire rotations without opening the fuel system, is exempt from many requirements for major repair garages. This exemption is primarily because:

Accepted Answer

the maintenance performed does not involve the sealed fuel system.

Answer

the facility services fewer than five CNG vehicles per day.

Answer

the service bay doors are required to be kept open during all service hours.

Answer

the facility has a high ceiling height of at least 20 feet.

Question 4

Which of the following is a key requirement for electrical equipment, such as lighting fixtures and junction boxes, located within 18 inches of the ceiling in a major CNG vehicle repair garage?

Accepted Answer

It must be rated for use in a Class I, Division 2 hazardous location.

Answer

It must be connected via a ground-fault circuit interrupter (GFCI).

Answer

It requires no special classification if a gas detection system is present.

Answer

It must be sealed with a standard vapor-tight enclosure.

Question 5

When a methane gas detection system is installed in a CNG maintenance facility, at what concentration must it activate an audible and visual alarm, according to NFPA 52?

Accepted Answer

At a concentration not exceeding 25% of the Lower Flammable Limit (LFL).

Answer

At exactly 50% of the Lower Flammable Limit (LFL).

Answer

At the moment the Lower Flammable Limit (LFL) of 5% is reached.

Answer

Only when the concentration reaches the Upper Flammable Limit (UFL).

Question 6

All of the following are specific facility design and equipment requirements for a major CNG repair garage under NFPA standards EXCEPT:

Accepted Answer

All personnel must wear certified flame-resistant clothing at all times.

Answer

The floor must be constructed of non-combustible materials.

Answer

Any below-grade pits must have their own dedicated mechanical ventilation system.

Answer

Heating equipment must be of a type and location that prevents ignition of potential gas leaks.