CNG Facility and Ventilation Requirements 3

Question 1

What minimum separation distance is typically required between a CNG dispensing unit and the nearest building opening such as a window or door?

Accepted Answer

10 feet

Answer

NFPA 52 requires CNG dispensers to be located at least 10 feet from building openings to prevent gas from entering the structure.

Question 2

In a CNG facility, what must automatically activate when a gas detector reaches 25% of the lower explosive limit (LEL)?

Accepted Answer

An audible and visual alarm

Answer

At 25% LEL, gas detection systems must trigger audible and visual alarms to alert personnel before concentrations reach dangerous levels.

Question 3

Which of the following facility configurations requires the highest level of ventilation per NFPA 52?

Accepted Answer

Fully enclosed CNG vehicle storage and maintenance building

Answer

Fully enclosed buildings trap gas most readily and therefore require the most stringent mechanical ventilation to maintain safe atmospheric conditions.

Question 4

What action must occur automatically when a gas detector in a CNG facility reaches 50% of the lower explosive limit?

Accepted Answer

Emergency shutoff of gas supply to the facility

Answer

At 50% LEL, NFPA 52 requires automatic emergency shutoff of the gas supply to prevent further accumulation and potential ignition.

Question 5

CNG storage cylinders located inside a building must be stored in an area that meets which ventilation requirement?

Accepted Answer

Ventilated to the outside at both high and low points

Answer

Storage areas for CNG cylinders must be ventilated at both high and low points to address any leakage regardless of whether the gas rises or condenses with heavier air components.

(CNG) Compressed Natural Gas Practice Test

(CNG) Compressed Natural Gas Practice Test

CNG Facility and Ventilation Requirements 3