Liquefied Petroleum & Compressed Natural Gas

What this means

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Official release

Source material from Arizona Department of Agriculture. The wording below is the issuer’s statement.

Alternative Fuel Standards & Oversight

The Arizona Department of Agriculture's Weights and Measures Services Division (WMSD) oversees the equity and accuracy of commercial transactions involving pressurized liquid and gaseous fuels. Whether verifying the exact volume of clean energy pumped into fleet vehicles or testing the filling accuracy of consumer exchange tanks, the division protects the marketplace through rigorous testing and device licensing protocols.

Fuel Classifications & Jurisdiction

What is LPG?

LPG stands for Liquefied Petroleum Gas, more commonly referred to as propane. Stored in a compressed liquid state, this product can consist of propane, propylene, pentane, butane, and/or butylene. It has an extensive variety of residential and commercial uses, serving as fuel for everything from backyard barbecue grills to school bus fleets.

What is CNG & LNG?

CNG (Compressed Natural Gas) consists primarily of methane and other light hydrocarbons stored in a highly compressed state. A sister product, LNG (Liquefied Natural Gas), shares a similar chemical composition but is super-cooled into a liquid state for storage and transport. Both products are heavily utilized to power clean-energy transit buses, regional refuse trucks, and long-haul commercial transport fleets.

Oversight & Jurisdiction Limits

Understanding state boundaries ensures your concerns are routed to the correct regulatory departments. WMSD maintains specific statutory enforcement targets:

What WMSD Regulates:

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Commercial LPG, CNG, and LNG meters and dispensers.

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Volumetric provers (pictured right on associated documents) to test LPG meter accuracy.

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Gravimetric conversion methods (converting weight to volume) to calibrate CNG/LNG meters.

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The labeled weight and quantity of propane in retail exchange cylinders and exchange tanks.

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Oversight and credentials for LPG and CNG Registered Service Agencies and Representatives.

What WMSD Does NOT Regulate:

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Residential and commercial bulk LPG tank structural placement and direct field installation.

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Physical propane cylinder expiration dates.

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State Fire Marshal codes and regulations relating to gas storage safety.

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Contractual delivery pricing agreements (unless there is a direct claim regarding commercial meter inaccuracy).

Consumer Protection & Resources

Consumer Tips for Smart Fueling

WMSD recommends taking active steps to ensure billing equity when purchasing propane or alternative natural gas:

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Verify the Zero: When refilling a cylinder or fueling your vehicle, confirm that the physical meter display starts exactly at zero before dispensing begins.

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Weight vs. Volume: Propane may legally be sold and refilled by weight in addition to volume. Because its chemical mixture varies, the total volume weight fluctuates slightly depending on component percentages.

Understanding Propane Weights & "Tare Weight"

Standard liquefied propane weighs exactly 4.2 pounds per gallon at 60°F. This structural metric dictates how tanks are commercially refilled by weight:

"Tare Weight" (TW) Explained

Tare Weight is the exact physical weight of an empty propane cylinder without any product inside.

State Consumer Law:

Retailers are strictly prohibited from charging consumers for the tare weight of a propane tank.

Identifying TW:

Propane tanks feature a tare weight value stamped directly onto the protective metal collar of the tank valve.

Example Stamp:

A stamp reading "TW 18" indicates the empty tank weighs exactly 18 pounds.

Interactive Alternative Fuel Resources

Connect with state and federal agencies to learn more about industry standards, clean energy initiatives, and safety codes:

U.S. DOE Natural Gas Basics ➔

Arizona Propane Gas Association ➔

About Propane: Energy for the Future (APGA) ➔

Release text attributed to Arizona Department of Agriculture. Consult the official publication for any subsequent corrections or updates.