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NIST Partners with NCWM and States for a National Survey on 20 lb Cylinders of LPG (Propane)

Photo of stacked 20 lb propane cyclanders
Credit: Iowa Weights and Measures Bureau

Over 10 billion gallons of Liquefied Petroleum Gas (Propane) were sold last year alone, including over 50 million individual cylinders of propane. The 20 lb LPG (Propane) cylinder is one of the more frequently used “convenience” products in U.S. households. Many of the U.S. State’s Weights and Measures authorities have found systematic and potentially significant problems with short weight (underfilled) 20 lb cylinders, but also with cylinders being filled beyond the safe capacity.

Thus, to ensure “Equity in the Marketplace,” the National Conference on Weights and Measures (NCWM), with support provided by the NIST Office of Weights and Measures (OWM), has initiated a National marketplace survey on LPG (Propane) 20 lb cylinders. The purpose of this survey is three-fold: 1) to collect contemporary data from the 2022 marketplace comparing the actual tare weight of a cylinder to the stamped tare weight; 2) to evaluate the Methods of Sale and fill procedures used at Direct Sale Refilling Locations; and 3) to determine net content compliance. This National survey not only represents a collaboration between NIST and NCWM but also represents a multi-purpose effort involving numerous state and local jurisdictions.

The U.S. Department of Transportation (DOT) issued a Final Rule (49 CFR § 178.35 “General Requirements for Specification Cylinders” in the Federal Register of December 28, 2020) that applies to cylinders manufactured after December 28, 2022.  The results obtained from this National survey may be used to inform the NCWM and states if they should petition the DOT to reconsider its regulations issued in the Final Rule before its implementation at the end of 2022. These requirements will preempt and significantly relax the requirements currently found in NIST Handbook 130.

Photo of Used and Evacuated 20 lb Cylinders
Photo of used and evacuated 20 lb cylinders in preparation for a Point of Pack Tare Weight (TW) assessment

The National survey will occur in three phases between February 2022 through April 2022 – Phase I: Point of Pack, Phase II: Direct Sale Refilling Stations, and Phase III: Exchange Locations. OWM has designed the data collection and coordination for each phase of the survey. An overview and training for officials participating in the LPG survey is scheduled for January 26, 2022 (see Weights and Measures Calendar of Events | NIST). Furthermore, the NCWM has prepared a series of training videos to assist surveyors with the data collection for each of the three phases of the survey. The analysis of the resultant survey data will also be supported by NIST’s Statistical Engineering Division.

Prior to Phase 1 (Point of Pack), NIST Office of Weights and Measures has provided an online training session to review instructions and intended outcomes.

Phase I: Point of Pack. Phase I is scheduled to occur during February 2022. The purpose is to determine the accuracy of the stamped tare weight compared to the actual tare weight of NEW and USED cylinders. This will be determined by data collected primarily at the plant location. A “plant,” for the purposes of this survey, is defined as a location where exchange cylinders are filled for shipment and sale to retail exchange locations. To ensure a survey-wide accurate assessment of tare weight, all cylinders for the various locations must be verified to be completely empty.

NCWM Video – Plant * (6:07 minutes):  Shows how to collect data at the plant and compares the accuracy of the stamped tare weight to the actual tare weight of NEW and USED cylinders.

Photo of a NC Inspector at an LPG Direct Sale Refilling Station
An example of a Direct Sale Refilling Station.
Credit: NC Department of Agriculture & Consumer Services (used with permission)

Phase II: Direct Sale Refilling Stations. Phase II is scheduled to occur during March 2022. The purpose is to collect data at Direct Sale Refilling Stations, documenting the Method of Sale, Price Posting and Filling Procedure. This information will be used to evaluate the impact that various marketing practices have on consumers and help determine whether the Method of Sale Regulation should be revised to add new requirements related to advertising and price posting.  For example, this may include unit pricing and clarified labeling requirements associated with exchange cages and LPG vending machines. 

NCWM Video – Direct Sale Refilling Locations* (2:47 minutes):  Shows the interview process to collect data at the Direct Sale Refilling Station only, documenting the Method of Sale, Price Posting and Filling Procedure.

Phase III: Exchange Locations. Phase III is scheduled to occur during April 2022. The purpose is to determine net weight compliance of 20 lb cylinders and assess how much product is left behind by customers when performing a cylinder exchange. The results are anticipated to demonstrate the impact of both underfill and overfill on both consumers and industry and may prompt the need for the development of new “good quantity control practices” for the LPG industry. The results may also be used to determine if current industry filling procedures are being followed. The results are anticipated to assist and inform states of any present need to better cooperate with their stakeholders (e.g., Propane Education and Research Council, National Propane Gas Association (NPGA), National Fire Protection Association, OSHA, U.S. DOT) to establish improved procedures and oversight.

NCWM Video – Exchange Locations* (7:04 minutes):  Shows how to determine net weight compliance of 20 lb cylinders and how to determine how much product consumers leave behind when performing a cylinder exchange.

Survey Data and Results. Upon completion of each phase, all survey data will be submitted to and collated by NIST, and then anonymized, analyzed, and summarized. The anonymized and summarized results will be provided to the NCWM Chair and Executive Director. A publicly available report of the results of the survey (with all data anonymized) is anticipated for Summer 2022.

If you need additional information or have any questions, or if you would like the participate in the survey (for one or all phases) as a representative of a state or local jurisdiction, please contact David Sefcik at david.sefcik [at]

*Videos are provided and shared with the permission of NCWM and are part of the NCWM YouTube site.

Released January 3, 2022, Updated February 15, 2022