MEMORANDUM 

To: Debbie Ottinger, U.S. EPA 

Cc: Sally Rand, Kirsten Cappel, U.S. EPA 

From: Paul Stewart, Mollie Averyt, and Deborah Harris, ICF International 

Date: June 28, 2010 

Re: The potential role of gas suppliers in weighing residual Fluorinated GHGs received 

from industry in relation to subpart I, DD, and SS reporting requirements (EP-W-07-

0068, Task Order 68, Task 2) 

The reporting requirements in the EPA Greenhouse Gas Mandatory Reporting Rule Subparts I, DD, and 

SS (electronics manufacture, electric power system, and electrical equipment manufacture, respectively) 

require that facilities track not only the amount of fluorinated greenhouse gases (F-GHGs) received from 

gas suppliers but also the amount returned to them. Each subpart proposed the same monitoring 

requirement that scales (or other instruments) used to measure quantities of gas must be certified to be 

accurate and precise to within 1 percent of the true weight (or of full scale in the case of subpart I). 

While some electronics manufacturers do estimate the amount of gas consumed at their facilities using 

“heel” factors and purchases, many use an IPCC default heel factor and have claimed in their public 

comments that the proposed accuracy and precision requirement is not feasible for the them to meet at 

their facility. Additionally, since electric power systems typically do not receive a credit for SF6 returned to 

the supplier, it has not historically been standard procedure for either the electric power system to weigh 

the cylinder to quantify the residual gas, or “heel”, or the gas supplier to provide this information to the 

utility.1

 Electrical equipment manufacturers have not specified via public comment whether they weigh 

returned cylinders or rely on suppliers to provide this service for them. 

Gas suppliers already measure the gas they supply to their customers and provide that information to 

their customers; however, it is less certain whether gas suppliers provide measurement services for the 

gas they receive back from their customers as the heel left in “empty”, returned cylinders. Since one 

option for facilities to meet the stated requirements of the rule may be to have gas suppliers provide 

measurement services for reporters, the purpose of this memorandum is to explore further the potential 

role of gas suppliers in weighing the returned amount of F-GHGs in order to help facilities comply with the 

stated regulatory requirements. 

The goal of ICF’s research on this topic was to investigate: 

• the weighing services gas suppliers provide; 

• the cost of these services; 

• the number of suppliers offering this service; and 

• whether the services could satisfy the proposed regulatory requirements. 

 

1

 The exception has been utilities that have participated in EPA’s SF6 Emission Reduction Partnership for Electric 

Power Systems. These Partner utilities have taken efforts to document the quantity of SF6 returned to suppliers for 

voluntary reporting purposes. 
I. Correspondence with Industry 

ICF contacted the following companies on the following dates:2

- Airgas (Bob Mueller) June 3, 2010; 

- AirProducts (Bob Ridgeway), June 4, 2010; 

- 3M (Kurt Werner), June 13, 2010 

Airgas Summary 

Bob Mueller of Airgas confirmed that any gas supplied to customers by Airgas is weighed using scales, 

and the weight is provided to customers. Airgas also provides a service to customers of weighing how 

much residual gas is returned to Airgas in cylinders as well as maintaining records of these residual 

amounts. However, this service involves an extra fee (the exact cost of the fee was not provided). 

Mr. Mueller also stated their scales have accuracies of +/- 2 lbs of true weight and that the 1% of true 

weight accuracy requirement in the proposed rule is not feasible for Airgas. However, he did state that the 

recalibration requirements in the proposed rule are more feasible and that Airgas already meets those 

requirements. He mentioned that Airgas will be submitting a formal public comment to EPA on the 

proposed rule, and asked that EPA reviews the public comment for more information (See Section II 

below). Since Airgas is not required to report emissions under the proposed rule, presumably their 

primary concern over the accuracy of their scales is whether they are capable of providing utilities with 

weights of returned gas that the utilities could then report under subpart DD. 

Mr. Mueller said that he cannot comment on the specific services provided by other gas suppliers in the 

industry, but he does not think there are any technical barriers that would prevent other gas suppliers 

from offering the same weighing services. 

Air Products Summary 

The following information was provided by e-mail: 

Gas cylinders at Air Products manufacturing and transfill facilities are weighed with scales to determine 

the product volume prior to shipment. While Air Products does measure the weight of residual gas 

returned for product tracking purposes, they do not perform this measurement individually for each 

cylinder, but rather for entire cylinder “batches” (to get a total weight returned). For larger packages 

(MEGC/ISO containers), individual containers are weighed at time of fill and time of return. 

While Air Products does not have specific information about their competitors’ individual practices, it is a 

common and widely recognized practice to weigh and report the fill volume of cylinders. Practices for 

recording and reporting residual quantities are more varied by suppliers. 

Air Products does not charge any customer a fee to weigh the cylinders or MEGC/ISO containers to 

determine the fill volume – nor were they aware of any competitor doing so. 

Air Products does not individually record residual quantities (i.e. heels) returned in cylinders, and 

therefore, cannot (and do not) report this information to customers. They do currently track and record 

residual quantities in MEGC/ISO containers – while customers do not currently request this information, it 

is available. 

Air Products uses scales with accuracies of < ± 1 % of weight as specified by manufacturer. The scales 

are calibrated every 6 months and a documented calibration/maintenance procedure is recorded in SAP. 

3M 

The following information was provided by e-mail: 

 

2

 ICF left messages with a representative at Honeywell twice in effort to obtain their input but did not ultimately make 

a connection. 

June 28, 2010 2
When providing F-Gases to semiconductor manufacturing facilities (or other electronics manufacturing 

facilities), 3M does measure with scales the quantity of gas supplied in all cylinders but typically does not 

weigh returned cylinders with heels. They will weigh returns that are destined for re-entrance to the 

process stream as well as returns to be scrapped.

When explained that electronics manufacturing facilities would keep a record of all gas received from and 

returned to suppliers and asked if this information is always communicated to the customers, the 

response provided was, “I am not sure who the “customer” is in this question. In general, it is felt that if we 

would need to take an action in support of a customer’s compliance, we would likely have a fee for that 

activity.” 

Their current scales do have an accuracy and precision of one percent of full scale or better. They 

calibrate annually at a minimum and in some cases, monthly. 

II. Public Comment 

Additional insight into this issue was provided via public comment on the proposed F-GHG rule. Select 

examples of commenters that provided such comments include: 

- SF6 Task Force of NEMA (including Airgas and US Electrical Equipment Manufacturers) 

- Matheson TriGas (EPA-HQ-OAR-2009-0927-0107) 

- Intel (EPA-HQ-OAR-2009-0927-0089) 

SF6 Task Force of NEMA (including Airgas and US Electrical Equipment Manufacturers) 

It can be inferred that “The Agency proposes to measure residual gas amounts to within one percent: 

“If the gas supplier weighs the new or residual gas, obtain from the gas supplier a detailed monthly 

accounting, within 1 percent, of new or residual gas amounts in the cylinders returned to the gas 

supplier.” 

NEMA is concerned that this level of accuracy will be unattainable in practice. SF6 gas is commonly 

shipped cylinders which have a nominal tare weight of 119 pounds. These cylinders are usually filled with 

115 pounds of gas. Users typically draw down the gas to about 10-14 pounds before returning the 

cylinder. The scales currently in use for revenue and accounting have an accuracy of ±2 pounds. If a gas 

cylinder is returned with 10 pounds of residual gas, the measurement would result in a potential gas 

weight error of 20 percent. Conversely, a 1 percent measurement of “new or residual gas amounts” would 

require a scale with an accuracy of ±0.1 pounds, or 200 times more precise than currently in use. While 

the proposed rule allows “best available” measurement accuracies in the 2011 reporting year, NEMA 

does not believe that 1 percent accuracy will be attainable by 2012. NEMA recommends that the EPA 

require accuracy no stricter than 10 percent for residual gas amounts.” 

Matheson TriGas 

“Specifically, we believe that MTG can provide a cost effective and efficient solution related to monitoring 

and measurement of gas “heel” in cylinders. In 40 CFR 98.94 (b) 1 – 6, USEPA proposes methods for 

measuring and monitoring the gas that remains in a cylinder after a company has discontinued its use. 

This is an important factor for quantifying the amount of gas that entered the process. 40 CFR 98.94(j) 

requires that the measurement devices used for this monitoring must have “an accuracy and precision of 

1 percent of full scale or better.” 

It is our understanding that many electronics manufacturers that will be subject to this regulation do not 

currently have the ability to measure gas heels to this level of precision. Many companies will struggle to 

install expensive flow meters in the short timeframe allowed by this proposed rule. 

MTG has a readily implementable and less expensive technology that will meet the USEPA's requirement 

for accuracy and precision of 1 percent for heel measurement of the cylinder/container. MTG employs a 

June 28, 2010 3
cost effective and integrated pressure sensing technology to monitor the contents contained in cylinder 

tanks. The EPA measurement criteria for accuracy and precision of 1 percent can be achieved through 

application and combined utilization of pressure transducing and "active" Radio Frequency Identification 

(RFID) technologies to monitor the live contents of the gas products filled in typical cylinder tanks. This 

integrated technology both measures and records the contents and usage of the materials extracted from 

the cylinder tanks on a continuous real time basis; the measurement is made under both dynamic 

(extracted use of gas from cylinder tanks) and static (no gas extracted from the cylinder tanks) operating 

conditions. The usage data associated with monitoring the live contents within each and every cylinder 

tank is captured within a dedicated operating system where all data resides for display and record 

purposes. Historical data logging of gas usage within predetermined time ranges can be recorded for 

graphical analysis and interpretation for review as necessary. 

The precision and accuracy of our system is 1 percent of full scale or better.” 

Intel 

Development of Heel Factors 

“Intel is concerned that the procedures proposed for quantifying cylinder “heels” (e.g. the residual material 

remaining when the cylinder is taken off line) may not be realistic. The procedure would require that a set 

cylinder change out point be set based on either a scale mass reading or a pressure transducer reading. 

This set point would have to be controlled within 1% to ensure that the amount of remaining material was 

consistent across every change and could therefore be accurately quantified. While we understand the 

need to quantify this material accurately, we don’t believe the 1% requirement is achievable or necessary. 

Some of the cylinders containing covered materials may hold as little as ten pounds of material when full. 

The amount of material remaining when the cylinder is changed may be as little as one pound or less. 

Therefore, this would require ensuring that the residual mass may vary by no more than .01 lbs each time 

the cylinder is changed. Not only is such a small quantity insignificant in terms of total emissions, but it is 

doubtful equipment can be found that can consistently measure to this level. Many existing gas cabinet 

scales are maintained to an accuracy of 1% or even better at full scale. However, this same accuracy as 

a percent of mass will not be achieved when the cylinder is consumed all the way down to the residual 

heel and only a fraction of the initial mass remains. Some very large containers are actually weighed with 

truck scales, which usually have increments of 10 or 20 lbs. The same point is true when cylinders are 

monitored by pressure instead of mass. Commonly used pressure transducers are accurate to 1% of full 

scale, or sometimes better. Again, this percent accuracy will not be achieved when only a fraction of the 

full scale mass remains and it will not be possible to manage residual heels within 1% consistently. Intel 

suggests that a more reasonable requirement is that cylinder changes be maintained within a limit of +/- 

10%, or +/- 5 lbs. mass, whichever is higher.” 

III. Summary of Information Available To-Date 

The responses above provide a good indication of the practices currently in place within industry. 

- Gas suppliers already meet many of the accuracy and precision requirements stated in the 

proposed subparts. However, this is not always the case, especially when there are relatively 

small quantities of gas being measured. 

- The practice of weighing residual gas in cylinders is varied from gas supplier to gas supplier. This 

practice may be currently available for individual cylinders (for a fee and per request of a 

customer), in bulk for batches of cylinders, individually for MEGC/ISO containers, or when the 

returns are to be reprocessed and recycled. 

It should be noted that: 

- Some electronics manufacturing facilities (specifically, semiconductor manufacturing facilities) 

have claimed that they do not currently meet the proposed accuracy and precision requirements 

and would have to either incur the cost of obtaining scales that do meet the requirements or incur 

the cost of services provided by gas suppliers who have scales that are one percent accurate. 

June 28, 2010 4
June 28, 2010 5

- In the current monitoring and QA/QC requirements for subpart DD, electric power systems are 

already required to weigh their beginning and end of year storage inventory using scales with the 

same precision and accuracy requirements as the scales used to weigh gas that is returned to 

suppliers. Therefore, electric power systems are not dependent on gas suppliers to perform the 

function of weighing gas that is returned to suppliers. However, since the gas suppliers are 

already performing the role of collecting used cylinders from the utility and recovering gas from 

the cylinders, it could very well be more cost-effective for electric power systems to pay gas 

suppliers to weigh returned gas than weighing the gas themselves. Gas suppliers would then 

need to ensure that they change their practices in order to meet the reporting requirements. 

- The electrical equipment manufacturers submitted their comments through the SF6 Task Force of 

NEMA. Their comments indicate that scales currently in use in their industry have an accuracy of 

±2 pounds, which will not meet the proposed accuracy and precision requirements.