Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.1 

CHAPTER 8 

OTHER PRODUCT MANUFACTURE 

AND USE 
Volume 3: Industrial Processes and Product Use 

8.2 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

Authors 

Sections 8.1, 8.2, and 8.3 

Deborah Ottinger Schaefer (USA) 

Friedrich Plöger (Germany), Winfried Schwarz (Germany), Sven Thesen (USA), Ewald Preisegger (Germany), 

Ayite-Lo N. Ajavon (Togo), and Dadi Zhou (China) 

Section 8.4 

Nigel Harper (UK) 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.3 

Contents 

8 Other Product Manufacture and Use.............................................................................................................8.6

8.1 Introduction...........................................................................................................................................8.6

8.2 Emissions of SF6 and PFCs from electrical equipment.........................................................................8.6

8.2.1 Introduction ...................................................................................................................................8.6

8.2.2 Methodological issues ...................................................................................................................8.7

8.2.2.1 Choice of method.....................................................................................................................8.7

8.2.2.2 Choice of emission factors.....................................................................................................8.14

8.2.2.3 Choice of activity data ...........................................................................................................8.17

8.2.2.4 Completeness.........................................................................................................................8.19

8.2.2.5 Developing a consistent time series.......................................................................................8.20

8.2.3 Uncertainty assessment ...............................................................................................................8.20

8.2.4 Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................8.21

8.2.4.1 Quality Assurance/Quality Control........................................................................................8.21

8.2.4.2 Reporting and Documentation ...............................................................................................8.22

8.3 Use of SF6 and PFCs in other products ...............................................................................................8.23

8.3.1 Introduction .................................................................................................................................8.23

8.3.2 Methodological issues .................................................................................................................8.23

8.3.2.1 Choice of method...................................................................................................................8.23

8.3.2.2 Choice of emission factors.....................................................................................................8.32

8.3.2.3 Choice of activity data ...........................................................................................................8.33

8.3.2.4 Completeness.........................................................................................................................8.33

8.3.2.5 Developing a consistent time series.......................................................................................8.33

8.3.3 Uncertainty assessment ...............................................................................................................8.33

8.3.4 Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................8.33

8.3.4.1 Quality Assurance/Quality Control........................................................................................8.33

8.3.4.2 Reporting and Documentation ...............................................................................................8.34

8.4 N2O from product uses........................................................................................................................8.35

8.4.1 Introduction .................................................................................................................................8.35

8.4.2 Methodological issues .................................................................................................................8.36

8.4.2.1 Choice of method...................................................................................................................8.36

8.4.2.2 Choice of emission factors.....................................................................................................8.36

8.4.2.3 Choice of activity data ...........................................................................................................8.37

8.4.2.4 Completeness.........................................................................................................................8.37

8.4.2.5 Developing a consistent time series.......................................................................................8.37

8.4.3 Uncertainty assessment ...............................................................................................................8.37

8.4.3.1 Emission factor uncertainties.................................................................................................8.37
Volume 3: Industrial Processes and Product Use 

8.4 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

8.4.3.2 Activity data uncertainties .....................................................................................................8.38

8.4.4 Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................8.38

References .....................................................................................................................................................8.39 

Annex 8A Examples of Tier 3 national SF6 inventory systems....................................................................8.41

Equations 

Equation 8.1 Default emission factor method.............................................................................................8.8 

Equation 8.2 Equipment disposal emissions under country-specific emission factor method....................8.9 

Equation 8.3 Tier 3 total emissions...........................................................................................................8.10 

Equation 8.4A Equipment manufacturing emissions - pure mass-balance..................................................8.10 

Equation 8.4B Equipment manufacturing emissions - hybrid .....................................................................8.11 

Equation 8.5A Equipment installation emissions - pure mass-balance .......................................................8.11 

Equation 8.5B Equipment installation emissions - hybrid...........................................................................8.11 

Equation 8.6A Equipment use emissions - pure mass-balance....................................................................8.11 

Equation 8.6B Equipment use emissions - hybrid.......................................................................................8.12 

Equation 8.7A Equipment disposal and final use emissions - pure mass-balance.......................................8.12 

Equation 8.7B Equipment disposal and final use emissions - hybrid..........................................................8.12

Equation 8.8 Emissions from recycling of SF6 .........................................................................................8.13 

Equation 8.9 Emissions from destruction of SF6 ......................................................................................8.13 

Equation 8.10 Utility-level mass-balance approach....................................................................................8.14 

Equation 8.11 Retiring nameplate capacity ................................................................................................8.18 

Equation 8.12 Emissions from AWACS (default emission actor)..............................................................8.24 

Equation 8.13 Emissions from AWACS (user mass-balance)....................................................................8.25 

Equation 8.14 University and research particle accelerator emissions (country-level) ..............................8.27 

Equation 8.15 University and research particle accelerator emissions 

(accelerator-level emission factor) ......................................................................................8.28 

Equation 8.16 Total research accelerator emissions ...................................................................................8.28 

Equation 8.17 Research accelerator emissions (accelerator-level mass-balance).......................................8.28 

Equation 8.18 Industrial/medical accelerator emissions (country-level) ....................................................8.30 

Equation 8.19 Adiabatic property applications...........................................................................................8.31 

Equation 8.20 Double-glazed windows: assembly .....................................................................................8.31 

Equation 8.21 Double-glazed windows: use...............................................................................................8.31 

Equation 8.22 Double-glazed windows: disposal .......................................................................................8.31 

Equation 8.23 Prompt emissions.................................................................................................................8.32 

Equation 8.24 N2O emissions from other product uses ..............................................................................8.36 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.5 

Figures 

Figure 8.1 Decision tree for SF6 from electrical equipment....................................................................8.8

Figure 8.2 Decision tree for SF6 from AWACS ...................................................................................8.24

Figure 8.3 Decision tree for SF6 from research accelerators.................................................................8.27

Figure 8.4 Decision tree for industrial and medical particle accelerators .............................................8.29

Figure 8A.1 Example of Tier 3 approach: Germany, High-Voltage equipment......................................8.42

Figure 8A.2 Example of Tier 3 approach: Germany, Medium-Voltage equipment ................................8.43

Tables 

Table 8.1 Avoiding double-counting or overlooking emissions: two examples..................................8.13

Table 8.2 Sealed pressure electrical equipment (MV Switchgear) containing SF6: 

default emission factors.......................................................................................................8.15

Table 8.3 Closed pressure electrical equipment (HV Switchgear) containing SF6: 

default emission factors.......................................................................................................8.16

Table 8.4 Gas insulated transformers containing SF6: default emission factors..................................8.16

Table 8.5 Uncertainties for default emission factors and lifetime .......................................................8.21

Table 8.6 Good practice reporting information for SF6 emissions 

from electrical equipment by tier.........................................................................................8.22

Table 8.7 SF6 emissions per plane per year.........................................................................................8.24

Table 8.8 National AWACS fleets ......................................................................................................8.25

Table 8.9 Average SF6 charge in a particle accelerator by process description...................................8.30

Table 8.10 Emission factor for each process description, (SF6 emissions from industrial 

and medical particle accelerators) .......................................................................................8.30
Volume 3: Industrial Processes and Product Use 

8.6 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

8 OTHER PRODUCT MANUFACTURE AND USE 

8.1 INTRODUCTION 

This chapter outlines methods for estimating emissions of sulphur hexafluoride (SF6) and perfluorocarbons 

(PFCs) from the manufacture and use of electrical equipment and a number of other products. It also provides 

methods for estimating emissions of nitrous oxide (N2O) from several products. In most of these applications, 

the SF6, PFC, or N2O is deliberately incorporated into the product to exploit one or more of the physical 

properties of the chemical, such as the high dielectric strength of SF6, the stability PFCs, and the anaesthetic 

effect of N2O. However, the applications discussed here have a wide range of emission profiles, ranging from 

immediate and unavoidable release of all of the chemical (e.g., use of PFCs as atmospheric tracers) to largely 

avoidable, delayed release from leak-tight products after 40 years of use (e.g., manufacture and use of sealedpressure electrical equipment). The estimation methods presented in the chapter have been tailored to reflect 

these differences in emission profiles. 

Section 8.2 details methods for estimating SF6 and PFC emissions from electrical equipment. Section 8.3 details 

methods for estimating emissions from the manufacture and use of a wide variety of other industrial, commercial, 

and consumer products that contain SF6 and PFCs, excluding those discussed elsewhere in this volume (e.g., 

PFC emissions from electronics manufacturing, which are discussed in Chapter 6). (Please see the introduction 

to Section 8.3 for the list of excluded sources.) Finally, Section 8.4 discusses methods for estimating N2O 

emissions from anaesthetics, propellants, and other product uses. 

8.2 EMISSIONS OF SF6 AND PFCs FROM 

ELECTRICAL EQUIPMENT 

8.2.1 Introduction 

Sulphur hexafluoride (SF6) is used for electrical insulation and current interruption in equipment used in the 

transmission and distribution of electricity. Emissions occur at each phase of the equipment life cycle, including 

manufacturing, installation, use, servicing, and disposal. Most of the SF6 used in electrical equipment is used in 

gas insulated switchgear and substations (GIS) and in gas circuit breakers (GCB), though some SF6 is used in 

high voltage gas-insulated lines (GIL), outdoor gas-insulated instrument transformers and other equipment. The 

aforementioned applications may be divided into two categories of containment. The first category is ‘Sealed 

Pressure Systems’ or ‘Sealed-for-life Equipment’, which is defined as equipment that does not require any 

refilling (topping up) with gas during its lifetime and which generally contains less than 5 kg of gas per 

functional unit.1 Distribution equipment normally falls into this category. The second category is ‘Closed 

Pressure Systems’, which is defined to include equipment that requires refilling (topping up) with gas during its 

lifetime. This type of equipment generally contains between 5 and several hundred kg per functional unit. 

Transmission equipment normally falls into this category. Both categories of equipment have lifetimes of more 

than 30 to 40 years. In Asia, significant quantities of SF6 are used in gas-insulated power transformers (GIT). 

Electrical equipment is the largest consumer and most important use of SF6, globally. It significantly contributes 

to worldwide SF6 emissions. However, the importance of this source varies considerably from region to region 

and from country to country. The emissions from this category depend not only on the installed (banked) or 

consumed quantities of SF6, but also very much on the tightness of the products and the handling processes 

applied. Regional average emission rates presently vary between far less than 1 percent to more than 10 percent. 

In general, emission rates have declined significantly since 1995. Targeted industry actions have reduced 

emissions by 50 to 90 percent in Europe and Asia (Ecofys, 2005; Aoyama, 2004). These actions include (1) 

 

1

 Formal definitions of ‘sealed-pressure system’ and ‘closed-pressure system’ are contained in International Electrotechnical Commission (IEC) Standard 60694. (IEC, 1996) 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.7 

designing equipment to require a smaller charge of SF6 and to be more leak tight and (2) improving handling 

processes and handling equipment for all life cycle stages.2 

In some regions (e.g., North America and Japan), perfluorocarbons (PFCs) are used as dielectrics and heat 

transfer fluids in power transformers. PFCs are also used for retrofitting CFC-113 cooled transformers. One PFC 

used in this application is perfluorohexane (C6F14). In terms of both absolute and carbon-weighted emissions, 

PFC emissions from electrical equipment are generally believed to be much smaller than SF6 emissions from 

electrical equipment; however, there may be regional exceptions to this pattern. 

8.2.2 Methodological issues 

8.2.2.1 CHOICE OF METHOD

Emissions of SF6 from electrical equipment can be estimated in a variety of ways with varying degrees of 

complexity and data intensity. This section describes good practice for using a Tier 1 method (the default 

emission-factor approach), a Tier 2 method (the country-specific emission-factor approach), and a Tier 3 

method (a hybrid that can use either mass-balance or emission-factor approaches for different life cycle stages, 

depending on country-specific circumstances). Generally, emissions estimates developed using the Tier 3 

method, which is implemented at the facility level, will be the most accurate. Estimates developed using the Tier 

1 method will be the least accurate. 

As is true for other emission sources, the tier selected will depend on data availability and whether or not the 

category is key. Figure 8.1, Decision Tree for SF6 from Electrical Equipment, summarises the process for 

choosing among Tiers 3, 2, and 1. Good practice in choosing between the mass-balance and emission-factor 

variants of the Tier 3 approach is discussed in detail in Section 1.5 of Chapter 1. This choice will depend both on 

data availability and on country-specific circumstances. As a first step in assessing the importance of SF6

emissions from electrical equipment and the other categories discussed in this chapter, inventory compilers are 

encouraged to contact chemical producers and suppliers as well as electrical equipment manufacturers and 

utilities and/or their industry associations. These organisations can provide basic information on chemical 

consumption and on equipment stocks and applications that can help the inventory compiler estimate emissions 

and identify sources that merit further investigation. They can also provide important advice and support in 

establishing more extensive data collection systems to support Tier 2 and Tier 3 estimates. 

 

2

 International Council on Large Electric Systems (CIGRE) has published a guide on SF6 handling, Guide for the Preparation 

of customized “Practical SF6 Handling Instructions,” Task Force B3.02.01, CIGRE Publication No.276, August 2005. 

(CIGRE, 2005) 
Volume 3: Industrial Processes and Product Use 

8.8 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

Figure 8.1 Decision tree for SF6 from electrical equipment1

Estimate emissions

using Tier 2 CountrySpecific Emission

Factor Approach.

Start

Can an

annual survey

of facilities that use SF6

be completed, gathering

data by lifecycle

stage?

Are

country-specific

emission factors

available?

Note:

1. In selecting an estimation method, it is good practice also to consider the criteria presented in Table 1.7, Chapter 1, Section 1.5 of this 

volume for choosing between the mass-balance and emission-factor variants of each tier.

2. See Volume 1 Chapter 4, Methodological Choice and Identification of Key Categories (noting Section 4.1.2 on limited resources), for 

discussion of key categories and use of decision trees.

3. It is good practice to contact National/Regional associations of utilities/users and manufacturers to collect, check, and 

aggregate actual and historical data.

Box 2: Tier 2

No

No

Is the

Other Product

Manufacture and Use a

key category2

, and is

this subcategory

significant?

Estimate emissions

using the Tier 1

Default Emission

Factor Approach.

Box 1: Tier 1

Yes

Estimate emissions

using Tier 3 Hybrid

Life-Cycle Approach.

Yes

Yes

Collect data for

Tier 2 or 3

approaches,3

Box 3: Tier 3

No

TIER 1 METHOD – DEFAULT EMISSION FACTORS 

The Tier 1 approach is the simplest approach for estimating SF6 and PFC emissions from electrical equipment. 

(Henceforth in this section, ‘SF6’ will be used to denote ‘SF6 and/or PFCs.’) In this method, emissions are 

estimated by multiplying default regional emission factors by, as appropriate, the SF6 consumption of equipment 

manufacturers and/or by the nameplate SF6 capacity of the equipment at each life cycle stage beyond 

manufacturing in the country. The term Installation Emissions may be omitted if (1) installation emissions are 

not expected to occur (i.e., for closed-pressure equipment) or (2) installation emissions are included in the 

emission factor for emissions from Manufacturing or Use. Default emission factors are given in Tables 8.2 to 8.4. 

It is good practice to use the following equation: 

EQUATION 8.1 

DEFAULT EMISSION FACTOR METHOD

Total Emissions = Manufacturing Emissions + Equipment Installation Emissions 

 + Equipment Use Emissions + Equipment Disposal Emissions 

Where: 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.9 

Manufacturing emissions = Manufacturing Emission Factor • Total SF6 consumption by equipment 

manufacturers 

Equipment installation emissions = Installation Emission Factor • Total nameplate capacity of new 

equipment filled on site (not at the factory). 

Equipment use emissions = Use Emission Factor • Total nameplate capacity of installed equipment. The 

‘use emission factor’ includes emissions due to leakage, servicing, and maintenance as well as 

failures 

Equipment disposal emissions = Total nameplate capacity of retiring equipment • Fraction of SF6

remaining at retirement 

TIER 2 METHOD – COUNTRY-SPECIFIC EMISSION FACTOR METHOD 

The Tier 2 method uses the same basic equation as Tier 1, but requires reliable country-specific emission factors 

for each life cycle stage. Country-specific emission factors will be more accurate because they reflect the unique 

circumstances in which electrical equipment is used in a given country. In addition, if detailed data for 

equipment retirement are available, emissions due to retirement can be estimated more accurately. The 

expression for Equipment Disposal Emissions in the Tier 2 method includes terms accounting for SF6 recovery 

at retirement and disposal, as follows: 

EQUATION 8.2 

EQUIPMENT DISPOSAL EMISSIONS UNDER COUNTRY-SPECIFIC EMISSION FACTOR METHOD

Equipment disposal emissions = Total nameplate capacity of retiring equipment • Fraction of SF6

remaining at retirement • (1 – fraction of retiring equipment whose SF6 is recovered • recovery 

efficiency • fraction of recovered SF6 recycled, reused with no further treatment, or destroyed*) 

*This final term is intended to account for emissions during chemical recycling and destruction. 

Note that to be considered Tier 2, estimates must be developed using only country-specific emission factors. 

TIER 3 HYBRID METHOD – EMISSIONS BY LIFE CYCLE STAGE OF 

EQUIPMENT 

The Tier 3 method is the most accurate approach for estimating actual emissions of SF6 from electrical 

equipment. This method is detailed but flexible, accommodating a wide range of national circumstances. The 

method is implemented at the facility level and includes separate equations for each phase of the life cycle of 

equipment, including equipment manufacture, installation, use, and disposal. Depending on the type of 

equipment, the life cycle stage, and country-specific circumstances, either a mass-balance approach or country- 

(or facility-) specific emission factors may be used. In general, it is good practice to use the mass-balance 

approach, except where (1) emission rates from a process are near or below the precision of the measurements 

required for the mass-balance approach (e.g., 3 percent of nameplate capacity per year or less), (2) equipment is 

never serviced during its lifetime (as is expected to be the case for sealed pressure equipment), or (3) equipment 

stocks are growing very rapidly, as may be the case in countries where electrical equipment has been introduced 

within the last 10-20 years. 

The hybrid approach enhances accuracy by permitting use of the mass-balance approach for some processes and 

life cycle stages and the emission-factor approach for other processes and life cycle stages. However, the 

combination of different approaches also introduces opportunities for double-counting or overlooking emissions. 

Inventory compilers need to be aware of this problem and take steps to avoid it. Table 8.1, Avoiding DoubleCounting or Overlooking Emissions, provides examples of both the problem and some potential solutions. 

The annex to this chapter (Annex 8A) briefly describes an example of the Tier 3 approach as it has been applied 

in Germany. This example is intended to illustrate rather than prescribe; the precise approach taken by any given 

country will depend on country-specific circumstances. 

Ideally, data are obtained for every equipment manufacturer, electricity transmission and distribution facility 

(utility), equipment disposer (which may be a manufacturer, electric utility, or other entity), and SF6 recycling or 

destruction facility in the country, and the emissions of all manufacturers, utilities, disposers, and recycling or 

destruction facilities are summed to develop the national estimate. The basic equation is: 
Volume 3: Industrial Processes and Product Use 

8.10 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

EQUATION 8.3 

TIER 3 TOTAL EMISSIONS

∑

∑

∑

∑

∑

+

+

+

+

=

Emissions from SF Recycling and Destruction

Equipment Disposal and Final Use Emissions

Equipment Use Emissions

Equipment Installation Emissions

Total Emissions Equipment Manufacturing Emissions

6

Where: 

Equipment Manufacturing Emissions at the facility level can be estimated by Equations 8.4A and 8.4B. 

Equipment Installation Emissions at the facility level can be estimated by Equations 8.5A and 8.5B. 

Equipment Use Emissions at the facility level can be estimated by Equations 8.6A and 8.6B. 

Equipment Disposal and Final Use Emissions at the facility level can be estimated by Equations 8.7A and 

8.7B. 

Emissions from SF6 Recycling and Destruction at the facility level can be estimated by Equations 8.8 and 

8.9. 

In the above equation, national emissions for each phase are equal to the sum of the emissions of all equipment 

manufacturers, equipment users, equipment disposers, or SF6 recyclers/destroyers at that phase. In practice, it is 

not always possible to obtain data for every facility; in these cases countries may use one of the extrapolation 

methods discussed in Section 8.2.2.3, Choice of Activity Data. 

Equipment manufacturing emissions 

Equipment manufacturing emissions can be estimated using either a pure mass-balance approach or a mixture 

(hybrid) of a mass-balance approach for some processes and an emission-factor based approach for others. The 

pure mass-balance approach is preferred except where a substantial fraction of a manufacturer’s emissions come 

from processes whose emission rates fall below the precision of the measurements required for the mass-balance 

approach (e.g., 3 percent of nameplate capacity per year or less). In these cases, it is good practice to use 

emission factors to estimate emissions from the processes with very low emission rates and to use the massbalance approach to estimate emissions from the other manufacturing processes. 

Pure mass-balance approach: Using the pure mass-balance approach, the total emissions of each equipment 

manufacturer can be estimated using the following equation: 

EQUATION 8.4A 

EQUIPMENT MANUFACTURING EMISSIONS - PURE MASS-BALANCE

6

6 6

Disbursements of SF

Equipment Manufacturing Emissions Decrease in SF Inventory Acquisitions of SF

−

= +

Where: 

Decrease in SF6 Inventory = SF6 stored in containers at the beginning of the year – SF6 stored in 

containers at the end of the year 

Acquisitions of SF6 = SF6 purchased from chemical producers or distributors in bulk + SF6 returned by 

equipment users or distributors with or inside of equipment + SF6 returned to site after off-site 

recycling 

Disbursements of SF6 = SF6 contained in new equipment delivered to customers + SF6 delivered to 

equipment users in containers + SF6 returned to suppliers + SF6 sent off-site for recycling + SF6

destroyed 

Hybrid approach: This method first requires that manufacturers separate the gas flows associated with processes 

for which the mass-balance approach will be used from the gas flows associated with processes for which the 

emission-factor approach will be used. Emissions from the former can then be estimated using the approach 

outlined in Equation 8.4A. Emissions from the latter can be estimated by multiplying the total nameplate 

capacity of equipment undergoing each process (e.g., filling) by the country- or facility-specific emission factor 

for that process. Total emissions for each manufacturer are then estimated by summing the emissions from both 

sets of processes, using the following equation: 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.11 

EQUATION 8.4B 

EQUIPMENT MANUFACTURING EMISSIONS - HYBRID

Emission factor for that process

Nameplate capacity of equipment undergoing each process

Equipment Manufacturing Emissions Equation A

•

+

=

∑ *

8.4

* Excluding that covered by Equation 8.4A 

Equipment installation emissions 

Equipment installation emissions may be estimated using either a mass-balance or an emission-factor approach. 

Again, the mass-balance approach is preferred except where emission rates are very low. 

Pure Mass-balance approach: Using the mass-balance approach, the total emissions of each equipment installer 

can be estimated using the following equation: 

EQUATION 8.5A 

EQUIPMENT INSTALLATION EMISSIONS - PURE MASS-BALANCE

Nameplate capacity of new equipment

Equipment Installation Emissions SF used to fill equipment

−

= 6

Hybrid approach: This method first requires that users separate the gas flows associated with equipment for 

which the mass-balance approach will be used from the gas flows associated with equipment for which the 

emission-factor approach will be used. Emissions from the former can then be estimated using the approach 

outlined in Equation 8.5A. Emissions from the latter can be estimated by multiplying the newly installed 

nameplate capacity of each equipment type by the country- or facility-specific installation emission factor for 

that type. Total emissions for each installer are then estimated by summing the emissions from both sets of 

equipments, using the following equation: 

EQUATION 8.5B 

EQUIPMENT INSTALLATION EMISSIONS - HYBRID

Nameplate capacity of new equipment filled on site Installation emission factor

Equipment Installation Emissions

+ •

=

∑ *

Equation 8.5A

* Excluding that covered by Equation 8.5A 

Equipment use emissions 

Equipment use emissions may be estimated using either a pure mass-balance or a hybrid approach. The pure 

mass-balance approach is likely to be appropriate for countries where (1) electrical equipment that uses SF6 has 

been in use for 10-20 years or more, and (2) emissions from sealed-pressure systems are likely to be negligible. 

The hybrid approach is likely to be appropriate for other countries. 

Pure mass-balance approach: Using the pure mass-balance approach, the total emissions of each equipment user 

can be estimated using the following equation: 

EQUATION 8.6A 

EQUIPMENT USE EMISSIONS - PURE MASS-BALANCE

SF recovered from closed pressure equipment at servicing

Equipment Use Emissions SF used to recharge closed pressure equipment at servicing

6

6

−

=

Hybrid approach: This method first requires that users separate the gas flows associated with equipment for 

which the mass-balance approach will be used from the gas flows associated with equipment for which the 

emission-factor approach will be used. Emissions from the former can then be estimated using the approach 

outlined in Equation 8.6A. Emissions from the latter can be estimated by multiplying the total nameplate 

capacity of each type of equipment by the country- or facility-specific emission factor for that type of equipment. 

The emission-factor approach is likely to be more accurate for sealed-pressure equipment everywhere and for all 
Volume 3: Industrial Processes and Product Use 

8.12 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

types of equipment in countries where electrical equipment has been used for less than 10-20 years. Total 

emissions for each user are then estimated by summing the emissions from both sets of equipment, using the 

following equation: 

EQUATION 8.6B 

EQUIPMENT USE EMISSIONS - HYBRID

Nameplate capacity of equipment installed Use emission factor

Equipment Use Emissions

+ •

=

∑ *

Equation 8.6A

* Excluding that covered by Equation 8.6A 

Equipment disposal and final use emissions 

Equipment disposal and final use emissions may be estimated using either a pure mass-balance or a hybrid

approach, based on country-specific circumstances. In both the pure mass-balance and hybrid approaches, 

emissions from closed-pressure equipment are estimated using a mass-balance equation. In the pure massbalance approach, emissions from sealed-pressure systems are also estimated using a mass-balance equation. In 

the hybrid approach, emissions from sealed-pressure systems are estimated using an emission-factor-based term. 

Pure mass-balance approach: In countries where the gas-collection infrastructure (including recovery equipment, 

technician training, and economic or legal incentives to recover) is not very well-developed or widely applied, it 

is good practice to use the pure mass-balance approach, as follows: 

EQUATION 8.7A 

EQUIPMENT DISPOSAL AND FINAL USE EMISSIONS - PURE MASS-BALANCE

Emissions from sealed pressure equipment (MB)

Disposal and Final Use Emissions Emissions from closed pressure equipment

+ ⋅

= ⋅

Where: 

Disposal and final use emissions from closed-pressure equipment = Nameplate capacity of retired closedpressure equipment – SF6 recovered from retired closed-pressure equipment, and 

Disposal and final use emissions from sealed-pressure equipment (MB) = Nameplate capacity of retired 

sealed-pressure systems – SF6 recovered from retired sealed-pressure systems 

Note that if the inventory compiler uses the emission-factor approach to estimate ‘use emissions’ from sealedpressure equipment, a term should be subtracted from the second equation to avoid double counting. See Table 

8.1, Avoiding Double-Counting or Overlooking Emissions: Two Examples, for this term. 

Hybrid approach: In countries where the disposal of equipment is well controlled and understood (i.e., where an 

efficient gas collection infrastructure is in place) and where emissions from use of sealed-pressure equipment are 

accounted for under ‘use’ above, the hybrid approach may be used, as follows:

EQUATION 8.7B 

EQUIPMENT DISPOSAL AND FINAL USE EMISSIONS - HYBRID

Emissions from sealed pressure equipment (EF)

Disposal and Final Use Emissions Emissions from closed pressure equipment

+

=

Where: 

Disposal and final use emissions from closed-pressure equipment = Nameplate capacity of retired closedpressure equipment – SF6 recovered from retired closed-pressure equipment, and 

Disposal emissions from sealed-pressure equipment (EF) = [(Nameplate capacity of retired sealedpressure systems) – (Nameplate capacity of retired sealed-pressure systems • Use emission factor •

Lifetime of equipment)] • (1 – fraction of retiring equipment whose SF6 is recovered • recovery 

efficiency) 

As noted above, emissions estimated using the above approach should be periodically checked, e.g., by using a 

pure mass-balance approach and/or assessing recovery frequency and practices. Inventory compilers should pay 

particular attention to the fraction of retiring equipment whose SF6 is recovered and to the fraction of the charge 

that is recovered when recovery is performed (‘recovery efficiency’). Even in countries where it is the norm to 

recover SF6 from retiring equipment, some venting may occur, and the venting of just a few percent of the SF6 in 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.13 

retiring equipment will drive emission rates far above the minimum that is technically achievable and that would 

otherwise be a reasonable basis for an emission factor. 

Emissions from SF6 recycling and destruction 

Some SF6 emissions occur after the chemical is recovered. These emissions include (1) emissions associated 

with recycling of SF6, and (2) emissions associated with the destruction of SF6. (Emissions associated with the 

shipment of SF6 to off-site recyclers or destruction facilities are considered negligible.) Emissions from recycling 

of SF6 are generally expected to be small — on the order of less than one percent of the total quantity fed into the 

recycling process. However, these emissions may be higher if state-of-the art handling equipment and practices 

are not used. In most cases, recycling is expected to occur on the site of the equipment manufacturer or user. In 

other cases, recycling may take place at a centralised recycling facility that is not associated with a chemical 

producer. Finally, recycling may take place on the premises of a chemical producer. Recycling emissions from 

chemical producers will be accounted for under chemical production (see Section 3.10 of this volume) and 

should not be included here. 

Emissions associated with the destruction of SF6 depend on the destruction efficiency of the process and the 

quantity of SF6 fed into the process. Given the high stability and dissociation temperature of SF6, the destruction 

efficiency may be as low as 90 percent. Thus, up to 10 percent of the SF6 fed into the destruction process could 

be emitted. The quantity of gas fed into the destruction process is generally expected to be small compared to 

that recycled. However, this may vary from country to country. 

It is good practice to develop country-specific emission factors for recycling and destruction that are based on 

full consideration of country-specific logistics and practices for SF6 recycling and destruction.

Emissions from recycling of SF6 may be estimated using the following equation: 

EQUATION 8.8 

EMISSIONS FROM RECYCLING OF SF6* 

Emissions from Recycling = Recycling emission factor • Quantity SF6 fed into recycling process 

*Emissions from recycling that occurs at chemical production facilities should be excluded. 

Emissions from destruction of SF6 may be estimated using the following equation: 

EQUATION 8.9 

EMISSIONS FROM DESTRUCTION OF SF6

Emissions from Destruction = Destruction emission factor • Quantity SF6 fed into destruction 

process 

TABLE 8.1 

AVOIDING DOUBLE-COUNTING OR OVERLOOKING EMISSIONS: TWO EXAMPLES

Example 1 – Double Counting Example 2 – Omission 

Situation: An emission-factor approach is used to 

estimate emissions from sealed-pressure equipment 

during use, and a mass-balance approach is used to 

estimate emissions during disposal of sealed-pressure 

equipment. 

Situation: A mass-balance approach is used to estimate 

emissions during use of closed-pressure equipment, but 

an emission-factor approach is used to estimate 

emissions during disposal of closed-pressure. 

Potential problem: Emissions during use may be 

double-counted because some of the SF6 that is found to 

be missing when the equipment is disposed has already 

been counted as emitted during use.

Potential problem: Emissions that occur between the 

final servicing of the equipment and its disposal may be 

overlooked. These ‘final use’ emissions may account for 

a significant fraction of total use emissions, particularly 

if the equipment is refilled every 10 years or more. 

Solution: Subtract lifetime use emissions (Nameplate 

capacity of retired sealed-pressure systems • Use 

emission factor • Lifetime of equipment) from emissions 

during disposal. 

Solution: Use the mass-balance approach for both the 

use and disposal phases of the closed-pressure equipment 

life cycle. 
Volume 3: Industrial Processes and Product Use 

8.14 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

A special case of the Tier 3 method: the utility-level, pure mass-balance 

approach 

Countries that satisfy the good practice criteria for using the pure mass-balance approach beyond equipment 

manufacturing (i.e., countries where emissions during equipment installation, use, and disposal account for 3 

percent or more of facility-level gas flows, where electrical equipment has been used for 10-20 years or more, 

and where emissions from sealed-pressure equipment are negligible), may, with little or no loss of accuracy, use 

a simplified version of the Tier 3 method to estimate emissions during equipment use. When summed together 

and reformulated in terms of facility-level gas flows, equations 8.5A, 8.6A, and 8.7A result in the following 

equation: 

EQUATION 8.10 

UTILITY-LEVEL MASS-BALANCE APPROACH

User Emissions = Decrease in SF6 Inventory + Acquisitions of SF6 – Disbursements of SF6 

– Net Increase in the Nameplate Capacity of Equipment 

Where: 

Decrease in SF6 Inventory = SF6 stored in containers at the beginning of the year – SF6 stored in 

containers at the end of the year 

Acquisitions of SF6 = SF6 purchased from chemical producers or distributors in bulk + SF6 purchased 

from equipment manufacturers or distributors with or inside of equipment + SF6 returned to site after 

off-site recycling 

Disbursements of SF6 = SF6 contained in equipment that is sold to other entities + SF6 returned to 

suppliers + SF6 sent off-site for recycling + SF6 destroyed 

Net Increase in Nameplate Capacity of Equipment = Nameplate Capacity of New Equipment – 

Nameplate Capacity of Retiring Equipment 

Although the utility-level approach is less detailed than the full life cycle approach, it is simple, and for those 

countries whose national circumstances permit its use, it provides estimates that are closely related to actual gas 

loss. 

SF6 EMISSIONS FROM MANUFACTURING OF ELECTRICAL COMPONENTS 

Some electrical equipment components may contain 1 percent or less by weight of SF6 in the insulating medium 

of the product. These components include but are not limited to medium voltage cast resin instrument 

transformers and high voltage bushings. In medium voltage (up to 52 kV) cast resin instrument transformers, SF6

is used to fill up micro-cavities in the resin insulation to improve the dielectric quality and durability of the 

product. In High Voltage (above 52 kV) bushings, SF6 is used as the blowing agent for the polyurethane resin in 

certain parts of the insulation system to improve the dielectric quality and durability of the product. 

SF6 emissions solely result from the casting/blowing process for the solid insulation of the product. All SF6 used 

is assumed to be emitted at the manufacturing stage. To estimate emissions from this source, the pure massbalance approach for equipment manufacturers (Equation 8.4A) may be used, setting the SF6 contained in new 

equipment equal to zero. 

Emission reduction measures focus on limiting losses/improving rate of recycling by suction devices and/or 

improved casting processes. SF6 in this type of high voltage bushings may be replaced by another blowing agent 

in the future. 

8.2.2.2 CHOICE OF EMISSION FACTORS

Because emission rates can vary not only from country to country but from facility to facility, inventory 

compilers using emission-factor based methods are encouraged to develop and use their own emission factors. 

Surveying a representative sample of equipment manufacturers and utilities within the country is an effective 

way to develop such factors. In general, it is good practice to document the evidence and reasoning supporting 

the selected emission factors, and to review these factors at least every 5 years. 

Factors that influence emission rates include the design of the equipment (which varies depending on when and 

where the equipment was manufactured), SF6-handling practices, availability of state-of-the-art handling 

equipment, SF6 prices, and regulations (e.g., recovery requirements). Variation of any one of these can change 

emission rates over time or among countries. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.15 

TIER 1 METHOD 

Suggested default emission factors have been developed for some regions based on recent research. These 

factors are shown in Tables 8.2-8.4 below. 

It is good practice to select default emission factors from countries and regions with equipment designs and SF6-

handling practices similar to those of the country whose emissions are being estimated. Because Japan and 

Europe supply most of the global demand for electrical equipment, equipment designs are likely to be similar to 

those of either Japan or Europe. With the exception of the factors for the U.S., regional default emission factors 

are those documented for 1995, i.e., before any special industry actions for emission reduction were 

implemented. In Japan in 1995, approximately 70 percent of the SF6 used to test equipment during manufacture 

was recovered, and a similar percentage was recovered during equipment maintenance for equipment rated 110 

kv or higher. (The 70 percent recovery fraction reflected recovery from an initial pressure of about 5 bars 

absolute to a final pressure of 1 to 1.5 bars absolute.) No gas was recovered from equipment rated lower than 

110 kV (Maruyama et al., 2000). In Europe in 1995, gas supply systems for equipment manufacture were usually 

decentralised, and filling tubes were not self-closing. Gas was recovered to approximately 0.05 bars absolute 

during manufacturing and maintenance (Ecofys, 2005). 

TABLE 8.2 

SEALED PRESSURE ELECTRICAL EQUIPMENT (MV SWITCHGEAR) CONTAINING SF6: 

DEFAULT EMISSION FACTORS 

Disposal 

(Fraction Nameplate Capacity of Disposed 

Equipment) 

Phase 

Region 

Manufacturing 

(Fraction SF6

Consumption by 

Manufacturers) 

Use (Includes leakage, 

major failures/arc faults 

and maintenance losses) 

(Fraction per Year of 

Nameplate Capacity of All 

Equipment Installed) 

Lifetime 

(years) 

Fraction of charge 

remaining at retirement b 

Europe a 0.07 0.002 >35 0.93 

Japan c 0.29 0.007 Not reported 0.95 

a

 Source: ‘Reductions of SF6 Emissions from High and Medium Voltage Electrical Equipment in Europe,’ Ecofys, June, 2005. 

b This refers to the percentage of the original charge or nameplate capacity remaining in the equipment at end of life; it represents the 

fraction of the nameplate capacity potentially emitted before the equipment is recycled or disposed. 

c

Based on data reported by the Federation of Electric Power Companies (FEPC) and the Japan Electrical Manufacturers’ Association

(JEMA) (FEPC and JEMA, 2004). These organisations did not distinguish among equipment types in reporting average emission 

factors. The factors are therefore intended to be applied to all equipment types, including sealed pressure systems, closed pressure 

systems, and gas-insulated transformers. 

Note: The emission factors above reflect the practices and technologies in place in 1995, i.e., before mitigation measures were

implemented. References per footnotes a and c show how these developed further upon successive implementation of various voluntary 

measures later on. Another reference (Schwarz, 2006) relates state-of–the-art emission factors to mitigation measures in Germany. 
Volume 3: Industrial Processes and Product Use 

8.16 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

TABLE 8.3 

CLOSED PRESSURE ELECTRICAL EQUIPMENT (HV SWITCHGEAR) CONTAINING SF6: 

DEFAULT EMISSION FACTORS 

Disposal 

(Fraction Nameplate Capacity of Disposed 

Equipment) 

Phase 

Region 

Manufacturing 

(Fraction SF6

Consumption by 

Manufacturers) 

Use (Includes leakage, 

major failures/arc faults 

and maintenance losses) 

(Fraction per Year of 

Nameplate Capacity of All 

Equipment Installed) 

Lifetime 

(years) 

Fraction of charge 

remaining at retirement c

Europe a 0.085b 0.026 >35 0.95 

Japan d 0.29 b 0.007 Not reported 0.95 

U.S.e f 0.14 g >35 h 

a

 Source: ‘Reductions of SF6 Emissions from High and Medium Voltage Electrical Equipment in Europe,’ Ecofys, June, 2005. 

b

 Includes emissions from installation 

c

 This refers to the percentage of the original charge or nameplate capacity remaining in the equipment at end of life; it represents the 

fraction of the nameplate capacity emitted before the equipment is recycled or disposed. 

d

 Based on data eported by the Federation of Electric Power Companies (FEPC) and the Japan Electrical Manufacturers’ Association

(JEMA) (FEPC and JEMA, 2004). These organisations reported average emission factors that include emissions from all equipment 

types, including sealed pressure systems, closed pressure systems, and gas-insulated transformers. 

e

 From the U.S. Inventory of Greenhouse Gases and Sinks, 1990-2002. (U.S. EPA, 2004). Value is from 1999, first year for which 

representative country-specific data were available. 

f No country-specific value available. 

g Includes emissions from installation. 

h

 Disposal emissions are included in use emission factor in the US. 

Note: The emission factors above reflect the practices and technologies in place in 1995, i.e., before mitigation measures were

implemented. References per footnotes a and d show how these developed further upon successive implementation of various voluntary 

measures later on. Schwarz (2006) relates state-of–the-art emission factors to mitigation measures in Germany. 

TABLE 8.4 

GAS INSULATED TRANSFORMERS CONTAINING SF6: DEFAULT EMISSION FACTORS 

Disposal 

(Fraction Nameplate Capacity of Disposed 

Equipment) 

Phase 

Region 

Manufacturing 

(Fraction SF6

Consumption by 

Manufacturers) 

Use (Includes leakage, 

major failures/arc faults 

and maintenance losses) 

(Fraction per Year of 

Nameplate Capacity of All 

Equipment Installed) 

Lifetime 

(years) 

Fraction of charge 

remaining at retirement a 

Japan b 0.29 0.007 Not reported 0.95 

a

 This refers to the percentage of the original charge or nameplate capacity remaining in the equipment at end of life; it represents the 

fraction of the nameplate capacity emitted before the equipment is recycled or disposed 

b

 Based on data reported by the Federation of Electric Power Companies (FEPC) and the Japan Electrical Manufacturers’ Association 

(JEMA) (FEPC and JEMA, 2004). These organisations did not distinguish among equipment types in reporting average emission 

factors. The factors are therefore intended to be applied to all equipment types, including sealed pressure systems, closed pressure 

systems, and gas-insulated transformers. 

Note: The emission factors above reflect the practices and technologies in place in 1995, i.e., before mitigation measures were

implemented. References per footnote b show how these developed further upon successive implementation of various voluntary 

measures later on. Schwarz (2006) relates state-of–the-art emission factors to mitigation measures in Germany.

TIER 2 METHOD 

Emission factors for the Tier 2 method are generally developed on the basis of data collected from representative 

manufacturers and utilities that track emissions by life cycle stage, essentially using the Tier 3, pure massbalance method at their facilities for at least one year. (The disposal emission factor should also account for 

emissions that occur downstream of the utility site, as discussed below.) These emissions by life cycle stage are 

then divided by the corresponding SF6 consumption or equipment capacity at that life cycle stage (i.e., SF6

consumption for manufacturing emissions, total existing equipment capacity for use emissions, and retiring 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.17 

equipment capacity for final use and disposal emissions) to develop emission factors. For example, to develop an 

emission factor for manufacturing, total emissions from the survey of manufacturers are summed and then 

divided by the total SF6 consumption of surveyed manufacturers. This emission factor can then be applied to the 

manufacturing sector as a whole, using national SF6 consumption by manufacturers. A similar approach can be 

used to estimate and apply emission factors for equipment use. 

The emission factor for disposal should fully account for three factors: (1) the recovery frequency (the fraction of 

equipment whose charge is recovered), (2) the recovery efficiency (the fraction of charge recovered when 

recovery is performed), and (3) the emissions from recycling and destruction of the recovered gas. The quantities 

in (1) and (2) will be automatically accounted for in emission factors based on use of the Tier 3 mass-balance 

method at representative utilities. However, the quantity in (3) reflects emissions that occur both on site and 

downstream of the utility/user. Thus, it must be accounted for separately. See the Tier 3 Method discussion 

below for guidance on estimating recycling and destruction emission factors. 

The facility-level variant of the Tier 3 approach may also be used to develop emission factors, but these will be 

applied at a more aggregated level, i.e., to equipment manufacturing and use (where the latter includes 

installation, use, and disposal) rather than to each lifecycle stage. 

TIER 3 METHOD 

Because the Tier 3 method encourages the use of emission factors only when emission rates from processes are 

quite low (e.g., 3 percent of nameplate capacity per year or less) or when electrical equipment has only recently 

been introduced into a country, emission factors for this method may be difficult to measure directly using a 

mass-balance approach. To estimate Tier 3 emission factors, therefore, engineering studies may be used, 

identifying potential leak points and loss mechanisms and assigning probabilities and emission rates to these. 

Expected losses from service and maintenance should be factored into overall emission rates, as should losses 

from rare but catastrophic events that result in the loss of most of the equipment’s charge. Past experience with 

similar processes and designs should be considered. To ascertain and verify emission factors for use, surveys of 

equipment in the field may be carried out after several years of use, with the number of years determined by the 

expected leak rate and the limit of detection of the measuring equipment. Manufacturer statistics on equipment 

failure rates should be monitored to help ensure that catastrophic or gradual loss rates are not higher than 

expected. Disposal emissions are extremely sensitive to recovery frequencies (the fraction of equipment whose 

charge is recovered) and to recovery efficiencies (the fraction of charge recovered when recovery is performed, 

which, due to time considerations, may be lower than what is technically achievable). Thus, these should be 

monitored and documented carefully before establishing disposal emission factors. 

Emission factors for recycling of recovered SF6 may be based on professional judgement. Emission factors for 

destruction may be based on the rated destruction efficiency of the destruction technology, assuming that the 

technology is maintained and operated in a way that maintains its rated destruction efficiency. 

8.2.2.3 CHOICE OF ACTIVITY DATA

The activity data necessary to carry out the various estimation methods may be gathered from chemical 

manufacturers, equipment manufacturers, equipment users, and equipment disposers and/or their industry 

associations in the country or the region. The best source(s) of data vary depending upon the method and 

national circumstances. 

TIER 1 METHOD 

SF6 consumption by equipment manufacturers: SF6 consumption by equipment manufacturers can be estimated 

using information from the manufacturers on their purchases of SF6, their returns of SF6 to chemical producers, 

and changes in their inventory of SF6 in containers. If information from equipment manufacturers is unavailable 

or incomplete, information from chemical producers and/or distributors on their sales to equipment 

manufacturers (less any returns) may be used. 

Nameplate capacity of new and retiring equipment: Nameplate capacity can be estimated using one 

or more of the following data sources: (1) information from equipment manufacturers/importers on the total 

nameplate capacity of the equipment they manufacture or import and export, (2) information from utilities on the 

total nameplate capacity of the equipment they install and retire each year, or (3) if information from (1) or (2) is 

not available, information from chemical manufacturers/importers on their sales of SF6 to equipment 

manufacturers. The first two data sources are preferable to the third, because gas sales to equipment 

manufacturers will differ from the nameplate capacity of new equipment installed in the country, particularly if 

equipment imports or exports are significant. In estimating the nameplate capacities of new and retiring 

equipment, inventory compilers should include the nameplate capacity of imported equipment and exclude the 
Volume 3: Industrial Processes and Product Use 

8.18 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

nameplate capacity of exported equipment. (See Section 7.5, Refrigeration, Box 7.1, Accounting for Imports and 

Exports of Refrigerant and Equipment, for a full discussion of how to treat imports and exports in estimating 

these quantities. This guidance is directly applicable to this category.) 

In the case of retiring equipment, capacity or sales information should be historical, starting in the year when the 

current year’s retiring equipment was built. Typical values for the lifetime of electrical equipment range from 30 

to 40 years. If information on the total nameplate capacity of retiring equipment is not available, it can be 

estimated from new nameplate capacity, using the estimated annual growth rate of equipment capacity. In 

estimating the growth rate, it is good practice to consider both the number of pieces of equipment sold each year 

and the average nameplate capacity of the equipment.3

 

The following equation can be used to estimate retiring nameplate capacity, if this information is not available 

directly: 

EQUATION 8.11 

RETIRING NAMEPLATE CAPACITY

Retiring Nameplate Capacity = New Nameplate Capacity / ( 1 + g )L 

Where: 

L = equipment lifetime 

g = rate of growth 

According to a 2004 global survey, the average annual growth rate of SF6 sales to equipment manufacturers 

between 1970 and 2000 was approximately 9 percent. (Smythe, 2004). In the absence of country-specific 

information, a default factor of 9 percent may be used. 

Total nameplate capacity of installed equipment: The total nameplate capacity of equipment can be 

estimated using the same data sources as are used to estimate the nameplate capacity for new and retiring 

equipment. If data from equipment manufacturers is used, it should include data on sales over the full lifetime of 

the equipment (30 to 40 years). 

TIER 2 METHOD 

Quantities can be estimated as for Tier 1 above. 

TIER 3 METHOD 

To implement the Tier 3 method, information must be gathered at two levels. At the facility level, gas flows 

must be tracked correctly according to the Tier 3 method. At the national level, information from facilities 

(manufacturers, users, and disposers of equipment) must be collected, checked, summed, and if necessary, 

extrapolated to include estimates of emissions from facilities in the country that do not collect data. Guidance 

regarding the information to be tracked by facilities is provided in the descriptions of the Tier 3 method above. 

Gas consumption may be measured by weighing gas cylinders before and after filling or recovery operations or 

at the beginning and end of the year or by using flow meters (e.g., during equipment manufacturing). At the 

national level, trade associations for equipment manufacturers and utilities can be very helpful in disseminating 

knowledge to their members regarding the Tier 3 approach and in helping their members to track and report data 

consistently and transparently. Trade associations can also act as third parties to aggregate confidential or 

sensitive data so that it can be released (in aggregate) to the public. Where trade associations are not active, 

national inventory compilers can facilitate the collection of information at the facility level, as well as the 

reporting and verification of this information, by developing model emission tracking protocols or by adopting 

existing industry protocols that embody the Tier 3 approach. These protocols can then be distributed to the 

manufacturers, users, and disposers of electrical equipment. Electronic protocols such as spreadsheets further 

facilitate the tracking, documentation, and reporting of emissions and minimize opportunities for arithmetic error. 

Because emission rates can vary from region to region and facility to facility, it is good practice to survey as 

many facilities as practical. In addition to manufacturers and utilities, countries should survey industrial sites and 

other non-utility sites if these contribute substantially to emissions from electrical equipment. If the number of 

facilities in a country is large (e.g., over 50), it may be difficult to achieve complete reporting. In these cases, 

countries may estimate emissions from non-reporting facilities by applying the Tier 2 method to these facilities 

 

3

 While the number of pieces of equipment sold each year has generally grown, the average nameplate capacity has generally 

declined. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.19 

or by using alternative activity data as described in Chapter 2 of Volume 1, Approaches to Data Collection. 

Sector-specific considerations in selecting and using alternative activity data are discussed below. 

For sealed pressure equipment (which is widely dispersed among industrial users as well as utilities), 

manufacturers and distributors are likely to be the best source of complete information on national bank sizes 

and emission rates. To develop an accurate estimate, inventory compilers should survey manufacturers regarding 

their sales of equipment between the present and the time when currently retiring equipment was installed, or, if 

equipment has not yet begun to be retired, between the present and the time when the equipment was introduced 

into the country. 

Sector-specific considerations in selecting and using alternative activity data 

for Tier 3 

As discussed above, even when implementing a Tier 3 method it may not be possible to obtain data from all 

facilities. To obtain complete coverage of facilities, it is possible to use alternative activity data. For estimating 

emissions from non-reporting manufacturers, it may be possible to use the manufacturing capacity and/or 

collective market share (in terms of functional units) of the non-reporting manufacturers. For estimating 

emissions from non-reporting utilities, possible alternative data sets or drivers include (but are not limited to) the 

length of transmission lines, the combined length of transmission and distribution lines, or the number of 

substations of the non-reporting utilities. Transmission kilometres are likely to be a good predictor of emissions 

where most SF6 is used in high voltage transmission equipment, as in the U.S. (A discussion of how transmission 

kilometres are used to estimate emissions in the U.S. can be found in Volume 1, Chapter 2, Approaches to Data 

Collection.) Where a high percentage of SF6 is used in medium voltage distribution equipment or in gasinsulated substations, one of the other types of data may be appropriate. 

Wherever alternative data sets are used, it is important to derive emission factors from a representative set of 

facilities to ensure that the resulting estimate of national SF6 emissions is unbiased. Note that more than one 

factor may be appropriate, e.g., for different size utilities or for utilities in urban vs. rural locations. Because SF6

use and emission patterns can change over time, it is good practice to update the analysis and emission factor(s) 

at least every five years. (For example, emission rates may change as compact and leak-tight equipment replaces 

larger, leakier equipment and as sealed pressure equipment grows in importance.) In some cases, countries may 

be able to make use of emission factors developed in countries with similar electrical grids. In these cases, it is 

good practice to document the similarities between the grids before applying the emission factor from the other 

country. 

8.2.2.4 COMPLETENESS

Completeness for this source category requires accounting for emissions during the manufacture, use, and 

disposal of equipment, and during the recycling or destruction of SF6 recovered from equipment. Where Tier 3 

methods are used, completeness requires that all significant SF6 users (manufacturers and utilities) be identified. 

When facility-level emissions data are not available from all of these users, emission estimates should be 

developed for them using one of the extrapolation methods described in Section 8.2.2.3, Choice of Activity Data. 

In the manufacturing sector, this requires assessing emissions from: 

• Manufacture of gas insulated switchgear (GIS), gas circuit breakers (GCB), high voltage gas-insulated lines 

(GIL), outdoor gas-insulated instrument transformers, reclosers, switches, and ring main units of both types 

(sealed and closed pressure systems, respectively up to and above 52 kV), and other equipment including 

but not limited to cast resin instrument transformers and certain types of bushings using SF6 either as gas for 

the casting process or as a blowing agent; 

• Manufacturers of gas-insulated power transformers (GIT); 

• Minor SF6 users, including equipment remakers and servicing companies; 

• The SF6 distribution chain from producers and distributors to manufacturing facilities. 

In the utility and disposal sector, this requires accounting for all SF6 losses associated with: 

• New electrical equipment installations; 

• Leakage, refill, maintenance, and equipment failures; 

• Disposal of discarded electrical equipment; 

• Recycling or destruction of SF6 recovered from equipment (but recycling emissions from chemical 

producers should be counted under chemical production, which is covered in Section 3.10 of this volume). 
Volume 3: Industrial Processes and Product Use 

8.20 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

It is good practice to identify and include industrial, military and small-utility applications if these are believed 

to contribute substantially to total emissions from the electrical equipment source category. 

8.2.2.5 DEVELOPING A CONSISTENT TIME SERIES

When estimating emissions from equipment users over a time series, it is necessary to consider SF6 emissions 

associated with the full set equipment at users’ sites for the years of interest. Thus, when using approaches based 

on banks and emission-factors (e.g., the Tier 2 approach), countries will require information on the capacity and 

emission rate of equipment purchased and installed for 30 to 40 years preceding the years of interest. 

In the user sector, if historical data are unavailable, good practice is to develop estimates using the top-down 

method, i.e., develop a model based on professional judgement by industry experts and inventory compilers and 

then calibrate as discussed below. Average leak rates for new equipment and the frequency of refill and routine 

maintenance all decreased from 1970 to 1995, and this trend has continued to the present. It is not good practice

to apply current (post-2000) overall loss rates to historical years. Aggregate loss rates estimated from historical 

sales can be used in this case as well. 

On the manufacturing side, if historical data for developing base year emissions for 1990/1995 are not available, 

the top-down method calibrated to more accurate estimates for current years may be applied. Since SF6 handling 

practices of equipment manufacturers have changed substantially since 1995 (e.g., more gas is recovered), it is 

not good practice to apply current loss rates to historical estimates. Aggregate loss rates determined from global 

and regional sales and emission analyses may assist in providing an unbiased estimate for earlier years. It is good 

practice to recalculate emissions according to the guidance provided in Volume 1, Chapter 5, with all 

assumptions clearly documented. 

8.2.3 Uncertainty assessment 

When using the Tier 3 method, the resulting emissions estimates will have an accuracy of the order of ± 10 

percent, and are likely to be more accurate than estimates developed using Tier 2 or Tier 1 methods.. If surveys 

are incomplete, the associated uncertainty will be greater. Particular sources of uncertainty may include: 

• SF6 exported by equipment manufacturers (either in equipment or separately in containers); 

• SF6 imported by foreign equipment manufacturers (either in equipment or in containers); 

• SF6 returned to foreign recycling facilities; 

• Measurements of mass, density, and pressure (generally accurate to within one or two percent of the total 

quantity massed, but if emission rates are low, this may be a substantial percentage of those rates); 

• Emission factors; 

• Time lag between emissions and servicing;4 

• Lifetime of the equipment; 

• Regression error associated with any extrapolative approaches. 

The estimated uncertainties in the default emission factors for the Tier 1 method are shown in Table 8.5, 

Uncertainties for Default Emission Factors for SF6 Emissions from Electrical Equipment. These values are based 

on the variation observed in emission factors in Europe. If the factors in Tables 8.2-8.4 are applied outside the 

countries and/or regions in which they were developed, uncertainties will be greater. 

 

4

 See Chapter 1 of this volume for a discussion of this issue. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.21 

TABLE 8.5 

UNCERTAINTIES FOR DEFAULT EMISSION FACTORS AND LIFETIME

Phase Disposal 

Equip 

-ment Type 

Manufacturi

ng 

Use (Includes leakage, 

major failures/arc faults 

and maintenance losses) Lifetime (years) Fraction of charge 

remaining at retirement

Sealed-Pressurea ±20% ±20% -20%/+40% d

Closed-Pressureb ±30% ±30% -10%/+40% d

Gas Insulated 

Transformers c ±30% ±30% -10%/+40% d

a Estimated from ‘Reductions of SF6 Emissions from High and Medium Voltage Electrical Equipment in Europe,’ Ecofys, June, 2005;no 

uncertainties available from Japan; not relevant for USA.. 

b

 Estimated from ‘Reductions of SF6 Emissions from High and Medium Voltage Electrical Equipment in Europe,’ Ecofys, June, 2005; 

U.S. emission factors have higher uncertainty for manufacturing (±70%) and slightly lower uncertainty for use (±15%) (U.S. 

Inventory of Greenhouse Gases and Sinks (U.S. EPA, 2004)). No uncertainties available from Japan. 

c Estimated by analogy with closed pressure systems; actual uncertainties may be somewhat higher. No uncertainties available from

Japan. 

d No uncertainties available on fraction of charge remaining at retirement.

8.2.4 Quality Assurance/Quality Control (QA/QC), 

Reporting and Documentation 

8.2.4.1 QUALITY ASSURANCE/QUALITY CONTROL

It is good practice to conduct quality control checks as outlined in Volume 1, Chapter 6, and an expert review of 

the emissions estimates. Additional quality control checks as outlined in Volume 1, and quality assurance 

procedures may also be applicable, particularly if higher tier methods are used to determine emissions from this 

source category. Inventory compilers are encouraged to use higher tier QA/QC for key categories as identified in 

Volume 1, Chapter 4. 

Additional procedures specific to electrical equipment are outlined below: 

Comparison of emissions estimates using different approaches 

Inventory compilers should sum the facility-level data used as part of a bottom-up, Tier 3 method and crosscheck the data against national level emissions calculated using country-level data (the Tier 2 method) and/or 

country-level data with the IPCC default emission factors (the Tier 1 method). The Tier 2 method may similarly 

be checked against the Tier 1 method. Countries may also compare their results to those derived using a countrylevel mass-balance approach, as described in Equations 7.3 and 7.9 of Chapter 7. If countries do not have 

manufacturing facilities, they may also compare their estimates against potential emissions estimated using 

national apparent consumption data. 

Review of facility-level emissions data 

In all instances where site-specific emissions data are obtained through surveys, inventory compilers should 

compare the emission rates between sites (adjusting for relative size or capacity) to identify significant outliers. 

They should investigate any outliers to determine if the differences can be explained or if there is an error in the 

reported emissions. As noted in Section 8.2.2.3, national inventory compilers can facilitate both the collection 

and verification of information at the facility level by distributing emission tracking protocols that embody the 

Tier 3 approach. Electronic protocols such as spreadsheets are particularly useful, as they minimize opportunities 

for arithmetic error. The calculations included in these protocols (whether electronic or not) can then be checked 

after they are submitted. 
Volume 3: Industrial Processes and Product Use 

8.22 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

Comparison of emission rates with those of other countries 

Inventory compilers should compare effective emission factors (loss rates) with values reported by other 

countries in the region, or with defaults published in the scientific literature for equipment with a similar design 

and similar level of emissions control. Transparent reporting, as outlined above, is essential for making 

international comparisons. 

8.2.4.2 REPORTING AND DOCUMENTATION

It is good practice to document and archive all information required to produce the national emissions inventory 

estimates as outlined in Volume 1, Section 6.11. It is not practical to include all documentation in the national 

inventory report. However, the inventory should include summaries of methods used and references to source 

data such that the reported emissions estimates are transparent and steps in their calculation may be retraced. 

Some examples of specific documentation and reporting relevant to this source category ensuring transparency 

in reported emissions estimates are provided in Table 8.6, Good Practice Reporting Information for SF6

Emissions from Electrical Equipment by tier. 

Confidentiality issues may arise where there are limited numbers of manufacturers or utilities. In these cases, 

aggregated reporting for the total electrical equipment sector, or even total national SF6 applications, may be 

necessary. National or regional associations of users and manufacturers may be willing to collect, check, and 

aggregate data, particularly when they have collected such data historically. They can then report the aggregated 

information to the inventory compiler, resolving the problem of confidentiality. If survey responses cannot be 

released as public information, third party review of survey data may be necessary to support data verification 

efforts. 

TABLE 8.6 

GOOD PRACTICE REPORTING INFORMATION FOR SF6 EMISSIONS FROM ELECTRICAL EQUIPMENT BY TIER

Data Tier 3 Tier 2 Tier 1 

Annual, country-wide consumption of SF6 by 

equipment manufacturers X X 

Nameplate capacity of new equipment X X X 

Nameplate capacity of existing equipment X* X X 

Nameplate capacity of retiring equipment X X X 

SF6 destroyed X 

SF6 in inventory at beginning of year X 

SF6 in inventory at end of year X 

SF6 purchased by facility X 

SF6 sold or returned by facility X 

SF6 sent off-site for recycling X 

SF6 returned to site after recycling X 

SF6 used to fill new equipment X 

SF6 used to service equipment X 

SF6 recovered from retiring equipment X 

Emission/recovery factors X* X 

Documentation for factors, if country-specific X* X 

*Required for some variants of the methods. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.23 

8.3 USE OF SF6 AND PFCs IN OTHER PRODUCTS 

8.3.1 Introduction 

This source category excludes the following source categories that are addressed elsewhere in the 2006 

Guidelines: 

• Production of SF6 and PFCs (Section 3.10); 

• Production and use of electrical equipment (Section 8.2); 

• Primary and secondary production of magnesium and aluminium (Chapter 4); and 

• Semiconductor and flat panel display manufacturing (Chapter 6). 

Identified remaining applications in this source category include: 

• SF6 and PFCs used in military applications, particularly SF6 used in airborne radar systems, e.g., AWACS 

(Airborne Warning and Control System), and PFCs used as heat transfer fluids in high-powered electronic 

applications; 

• SF6 used in equipment in university and research particle accelerators; 

• SF6 used in equipment in industrial and medical particle accelerators; 

• ‘Adiabatic’ applications utilising the low permeability through rubber of SF6 and some PFCs, e.g., car tires 

and sport shoe soles; 

• SF6 used in sound-proof windows; 

• PFCs used as heat transfer fluids in commercial and consumer applications; 

• PFCs used in cosmetics and in medical applications; 

• Other uses e.g. gas-air tracer in research and leak detectors. 

8.3.2 Methodological issues 

8.3.2.1 CHOICE OF METHOD

The good practice method is to use either consumption data from users of SF6 or PFCs or top-down import, 

export and consumption data from national SF6 producers and distributors, disaggregated by major type of SF6 or 

PFC application. Acquiring this data will entail a survey of all producers and distributors of SF6 and PFCs to 

identify total net SF6 and PFC consumption. Once the data are obtained, the amount of SF6 and PFC consumed 

by application in this source category should be estimated. 

MILITARY APPLICATIONS 

SF6 EMISSIONS FROM OPERATION OF AWACS 

SF6 is used as an insulating medium in the radar systems of military reconnaissance planes of the Boeing E-3A 

type, commonly known as AWACS. The purpose of the SF6 is to prevent electric flashovers in the hollow 

conductors of the antenna, in which high voltages of more than 135 kV prevail. When the plane ascends, SF6 is 

automatically released from the system and into the atmosphere to maintain the appropriate pressure difference 

between the system and the outside air. When the plane descends, SF6 is automatically charged into the system 

from an SF6 container on board. Most emissions occur during the pressure-balancing process on ascent, but 

emissions from system leakage can also occur during other phases of flight or during time on the ground. Annual 

emissions per plane have been estimated to be 740 kg, while the charge of each system is approximately 13 kg. 
Volume 3: Industrial Processes and Product Use 

8.24 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

Figure 8.2 Decision tree for SF6 from AWACS 

Use Emission-Factor

Tier 1 approach.

Start

Are detailed

acquisition and

disbursement data available

for this

category?

Is the Other

Product Manufacture

and Use a key category1

, and is 

this subcategory

significant?

Note:

1. See Volume 1 Chapter 4, Methodological Choice and Identification of Key Categories (noting Section 4.1.2 on limited resources), for 

discussion of key categories and use of decision trees.

Box 2: Tier 2

No

No

Box 1: Tier 1

Yes

Use Mass-Balance

Tier 2 approach.

Yes

Collect data for 

Tier 2 method.

Tier 1 method – SF6 emissions per plane 

If a country does not have data on SF6 consumption by its AWACS, it may use a per-plane emission factor to 

estimate emissions. An emission factor of 740 kg per plane per year is presented in Table 8.7 below; this figure 

is based on estimates of SF6 emissions from NATO Boeing E-3As. Note that actual emissions per plane are 

strongly influenced by the average number of sorties (take-offs) per plane per year. More frequent sorties will 

raise the emission rate above 740 kg/plane; less frequent sorties will lower it. Leakage rates during flight or 

during time on the ground will also affect the emission rate. 

EQUATION 8.12 

EMISSIONS FROM AWACS (DEFAULT EMISSION ACTOR) 

User Emissions = 740 kg • Number of planes in AWACS fleet 

TABLE 8.7 

SF6 EMISSIONS PER PLANE PER YEAR

Emissions per plane per year (kg SF6) Uncertainty 

740 kg ±100 kg 

Source: Schwarz (2005) 

Table 8.8 includes information on national AWACS fleets world wide (Boeing, 2005); like other activity data, it 

may quickly go out of date. Countries are in the best position to know the numbers of planes in their AWACS 

fleets. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.25 

TABLE 8.8 

NATIONAL AWACS FLEETS

Country/ 

Organisation 

USA Japan France UK Other 

NATO 

Saudi 

Arabia 

Total 

No. AWACS 33 4 4 7 17 5 70 

Source: Boeing (2005) 

Tier 2 method – user mass-balance method 

The most accurate method for estimating SF6 emissions from AWACS is to track SF6 consumption by the 

systems. To do so, the following equations, which are similar to the utility-level variant of the Tier 3 method for 

electrical equipment, may be used. Note that for AWACS, acquisitions and disbursements of SF6 containers are 

likely to be considerably more important to the result than acquisitions and retirements of operating systems. 

EQUATION 8.13 

EMISSIONS FROM AWACS (USER MASS-BALANCE) 

User Emissions = Decrease in SF6 Inventory + Acquisitions of SF6 – Disbursements of SF6 – Net 

Increase in AWACS Fleet Charge 

Where: 

Decrease in SF6 Inventory = SF6 stored in containers at the beginning of the year – SF6 stored in 

containers at the end of the year 

Acquisitions of SF6 = SF6 purchased from chemical producers or distributors in bulk + SF6 purchased 

from AWACS manufacturers or distributors with or inside of new planes + SF6 returned to site after 

off-site recycling 

Disbursements of SF6 = SF6 contained in AWACS that are transferred to other entities + SF6 returned to 

suppliers + SF6 sent off-site for recycling + SF6 destroyed 

Net Increase in AWACS Fleet Charge = 13 kg • (New AWACS – Retiring AWACS) 

SF6 AND PFC EMISSIONS FROM OTHER MILITARY APPLICATIONS 

There is wide range of military applications using PFCs or SF6.

5 Military electronics are believed to be an 

important and growing application of PFC heat transfer fluids, which are valued for their stability and dielectric 

properties. The fluids are used in ground and airborne radar (klystrons), avionics, missile guidance systems, 

ECM (Electronic Counter Measures), sonar, amphibious assault vehicles, other surveillance aircraft, lasers, SDI 

(Strategic Defense Initiative), and stealth aircraft. PFCs may also be used to cool electric motors, particularly in 

applications where noise reduction is valued, e.g., in ships and submarines. The specific PFCs used in these 

applications are believed to be similar to those identified as heat transfer fluids in electronics manufacturing in 

Chapter 6. Spray cooling, jet impingement cooling, and pool boiling appear to be the favoured systems for heat 

removal. In all of these cooling applications, the PFC is contained in a closed system, and neither replacement 

nor replenishment of the PFC liquid appears to be required. Thus, the greatest opportunities for emissions are the 

manufacture, maintenance, and, especially, the disposal of the equipment. 

SF6 is used in high-performance ground and airborne radar systems in their hollow conductors for transmission 

of high-frequency energy pulses at high voltages from the klystron. Another application of SF6 is as an oxidant 

of lithium in Stored Chemical Energy Propulsion System (SCEPS), e.g., in naval torpedoes and in infrared 

decoys (Koch, 2004). Apparently, these applications of SF6, like those of the PFC heat transfer fluids 

enumerated above, are generally more or less enclosed, but servicing and testing procedures may lead to 

emission. The use of SF6 for the quieting of torpedo propellers has also been reported (NIST, 1997).

In addition, SF6 may be emitted as a by-product of the processing of nuclear material for the production of fuel 

and nuclear warheads. SF6 is known to be emitted from neutralising excess fluorine during the production of 

nuclear fuel for civilian applications (AREVA, 2005). 

 

5

 David Harris and James Hildebrandt, “Spray Cooling Electrical and Electronic Equipment,” COTS Journal, November 

2003; C. Shepherd Burton, “Uses and Air Emissions of Liquid PFC Heat Transfer Fluids from the Electronics Sector,” 

Draft report prepared for Scott C. Bartos, U.S. Environmental Protection Agency. 
Volume 3: Industrial Processes and Product Use 

8.26 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

Although it is believed that the total amounts of SF6 and PFCs consumed and emitted in this sector may be 

significant, no data on quantities are publicly available so far. Therefore, inventory compilers should try to 

collect further information from the relevant authorities and, if possible, their suppliers. As noted above, the 

greatest opportunities for emissions from many of these applications appear to be the manufacture, maintenance, 

and disposal of the equipment. Thus, if inventory compilers can acquire information on emission rates during the 

manufacture, maintenance, and disposal of the equipment, along with the quantities of equipment manufactured, 

in use, and disposed, they can use the Tier 2 or Tier 3 method for electrical equipment to estimate emissions. For 

applications with different emissions profiles (e.g., prompt emissions), the appropriate equation from Section 8.2 

may be used. 

SF6 EMISSIONS FROM UNIVERSITY AND RESEARCH PARTICLE 

ACCELERATORS 

SF6 is used in university and research operated particle accelerators as an insulating gas. Typically, high voltage 

equipment is contained and operated within a vessel filled with SF6 at a pressure exceeding atmospheric pressure. 

Charges range from five kilograms to over ten thousand kilograms, with typical charges falling between 500 and 

3 000 kg. When the equipment requires maintenance, the SF6 is transferred into storage tanks. SF6 losses occur 

primarily during gas recovery and transfer, when pressure relief valves are actuated, and through slow leaks. 

Based on two recent studies annual SF6 losses range between 5 and 7 percent of vessel capacity per year and 

generally depend on the vessel opening frequency plus the efficiency of the recovery and transfer equipment. 

World banked capacity is roughly estimated to be 500 tonnes with annual SF6 emissions of 35 tonnes. 

Switzerland has developed a voluntary program to reduce SF6 emissions from particle accelerators. Suggestions 

and techniques for reducing SF6 emissions from these sources exist. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.27 

Figure 8.3 Decision tree for SF6 from research accelerators 

Use Accelerator-Level

Emission-Factor approach.

Start

Are

detailed acquisition

and disbursement data 

available for this 

category?

Are

data on individual 

accelerator charges 

available?

Note:

1. See Volume 1 Chapter 4, Methodological Choice and Identification of Key Categories (noting Section 4.1.2 on limited resources), for 

discussion of key categories and use of decision trees.

Box 3: Tier 3

No

Yes

Box 1: Tier 1

Yes

Use Accelerator-Level

Mass-Balance approach.

No

Collect data for Tier 3

or Tier 2 method.

Is the

Other Product

Manufacture and Use 

a key category1, and is this

subcategory

significant?

Box 2: Tier 2

Use Country-Level

approach. No

Yes

Tier 1 method – country-level method 

In cases where individual user accelerator charge data is unavailable, one extremely rough method involves 

determining the total number of university and research particle accelerators in the country and using several 

factors to determine the country-level annual emission rate as noted in Equation 8.14. For this Tier 1 method, the 

only data that requires collection is the total number of university and research particle accelerators in the given 

country. 

EQUATION 8.14 

UNIVERSITY AND RESEARCH PARTICLE ACCELERATOR EMISSIONS (COUNTRY-LEVEL) 

Emissions = (Number of university and research particle accelerators in the country) • (SF6 Use 

Factor) • (SF6 Charge Factor, kg) • (SF6 university and research particle accelerator Emission Factor) 

Where: 

Number of university and research particle accelerators in the country = The total number of university 

and research particle accelerators in the country. This rough method does not require countries to 

determine the number of accelerators that use SF6. To determine if a country has a particle 

accelerator, go to http://www-elsa.physik.uni-bonn.de/Informationen/accelerator_list.html 
Volume 3: Industrial Processes and Product Use 

8.28 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

SF6 Use Factor = 0.33 Approximately one third of university and research particle accelerators use SF6 as 

an insulator. 

SF6 Charge Factor = 2400 kg, SF6, the average SF6 charge in a university and research particle 

accelerator. 

SF6 university and research particle accelerator Emission Factor = 0.07, the average annual university 

and research particle accelerator emission rate as a fraction of the total charge. 

Tier 2 method – accelerator-level emission-factor approach 

If data on the quantity of SF6 contained within each university and research accelerator are available, a default 

emission factor of 7 percent may be multiplied by the total SF6 charge contained in university and research 

accelerators in the country. The total country SF6 emission rate from university and research accelerators is 

therefore calculated from Equation 8.15. 

EQUATION 8.15 

UNIVERSITY AND RESEARCH PARTICLE ACCELERATOR EMISSIONS (ACCELERATOR-LEVEL 

EMISSION FACTOR) 

Total Emissions = SF6 university and research particle accelerator Emission Factor 

• ∑ Individual Accelerator Charges 

Where: 

SF6 university and research particle accelerator Emission Factor = 0.07, the average annual university 

and research particle accelerator emission rate as a fraction of the total charge. 

Individual User Accelerator Charges = SF6 contained within each university and research accelerator. 

Tier 3 method –accelerator-level mass-balance method 

SF6 emissions from university and research facilities operating particle accelerators may be most accurately 

determined at the user level on an accelerator-by-accelerator basis. Emission calculations are estimated by 

tracking accelerator charge as well as SF6 consumption and disposal. As detailed in Equation 8.16, the total 

emissions are equal to the sum of the individual users’ emissions. Note, under this method, as the overall SF6

emission rate from particle accelerators is small compared to other SF6 uses, the associated SF6 lost in 

manufacturing is considered negligible and is not included in the calculation. 

EQUATION 8.16 

TOTAL RESEARCH ACCELERATOR EMISSIONS

Total Emissions = ∑ Individual Accelerator Emissions

Each particle accelerator’s emissions can be calculated as follows: 

EQUATION 8.17 

RESEARCH ACCELERATOR EMISSIONS (ACCELERATOR-LEVEL MASS-BALANCE) 

Accelerator Emissions = Decrease in SF6 Inventory + Acquisitions of SF6 – Disbursements of SF6

– Net Increase in Accelerator Charge 

Where: 

Decrease in SF6 Inventory = SF6 stored in containers at the beginning of the year – SF6 stored in 

containers at the end of the year 

Acquisitions of SF6 = SF6 purchased from chemical producers or distributors in bulk + SF6 purchased 

from accelerator manufacturers or distributors with or inside of new accelerator components + SF6

returned to site after off-site recycling 

Disbursements of SF6 = SF6 contained in components transferred to other entities + SF6 returned to 

suppliers + SF6 sent off-site for recycling + SF6 destroyed 

Net Increase in Accelerator Charge = SF6 Charge of New Components – SF6 Charge of Retiring 

Components 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.29 

SF6 EMISSIONS FROM INDUSTRIAL AND MEDICAL PARTICLE 

ACCELERATORS 

SF6 is used as an insulating gas in two types of industrial particle accelerators (low and high voltage) and also in 

medical (cancer therapy) particle accelerators, as is the case for university and research particle accelerators. 

However, the emission and charge factors for industrial and medical particle accelerators are different from those 

of university and research accelerators, as discussed below. 

Global banked capacity for industrial particle accelerators is roughly estimated to be 500 tonnes with annual SF6

emissions of 35 tonnes. Global banked capacity for medical (radiotherapy) particle accelerators is roughly 

estimated to be less than 5 tonnes with annual SF6 emissions of less than 5 tonnes. (Schwarz, 2005). 

Figure 8.4 Decision tree for industrial and medical particle accelerators 

Use User-Level EmissionFactor approach.

Start

Are detailed

acquisition and disbursement 

data available for this

category?

Are

data on individual

accelerator charges

available?

Note:

1. See Volume 1 Chapter 4, Methodological Choice and Identification of Key Categories (noting Section 4.1.2 on limited resources), for 

discussion of key categories and use of decision trees.

Box 3: Tier 3

No

Yes

Box 1: Tier 1

Yes

Use User-Level MassBalance approach.

No

Collect data for Tier 3

or Tier 2 method.

Is the Other

Product Manufacture

and Use a key category1

, and is

this subcategory

significant?

Box 2: Tier 2

Use Country-Level

approach. No

Yes

Tier 1 method – country-level method 

In cases where individual user accelerator charge data is unavailable, one extremely rough method involves 

determining the total number of particle accelerators by process description in the country and using factors to 
Volume 3: Industrial Processes and Product Use 

8.30 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

determine the country level annual emission rate as noted in Equation 8.18. For this Tier 1 method, the only data 

that requires collection is the total number of particle accelerators which contain SF6 by process description in 

the given country. 

EQUATION 8.18 

INDUSTRIAL/MEDICAL ACCELERATOR EMISSIONS (COUNTRY-LEVEL) 

Emissions = (Number of particle accelerators that use SF6 by process description in the country) •

(SF6 Charge Factor, kg) • (SF6 applicable particle accelerator Emission Factor) 

Where: 

Number of particle accelerators by type in the country = The total number of particle accelerators by type 

(industrial high voltage, industrial low voltage and radiotherapy) that use SF6 in the country, 1, 2, etc. 

(Only count particle accelerators that use SF6. This differs for the Tier 1 calculation for university 

and research particle accelerators) 

SF6 Charge Factor = The average SF6 charge in a particle accelerator by process description as noted 

below. 

SF6 particle accelerator Emission Factor = The average annual SF6 particle accelerator emission rate as a 

fraction of the total charge by process description. 

TABLE 8.9 

AVERAGE SF6 CHARGE IN A PARTICLE ACCELERATOR BY PROCESS DESCRIPTION

Process Description SF6 Charge Factor, kg 

Industrial Particle Accelerators – high voltage (0.3-23 MV) 1300 

Industrial Particle Accelerators –low voltage (<0.3 MV) 115 

Medical (Radiotherapy) 0.5a 

a

 This is the average of values ranging from 0.05 kg to over 0.8 kg, depending on model and manufacturer. 

Source: Schwarz (2005) 

Tier 2 method – user-level emission-factor approach 

If data on the quantity of SF6 contained within each industry and medical accelerator are available, use the Tier 2 

method for university and research facilities; however, multiply the emission factor for each process description 

provided below by the total, country-specific SF6 charge for that process description. 

TABLE 8.10 

EMISSION FACTOR FOR EACH PROCESS DESCRIPTION, 

(SF6 EMISSIONS FROM INDUSTRIAL AND MEDICAL PARTICLE ACCELERATORS) 

Process Description Emission Factor, kg /kg SF6 charge 

Industrial Particle Accelerators – high voltage (0.3-23 MV) 0.07 

Industrial Particle Accelerators – low voltage (<0.3 MV) 0.013 

Medical (Radiotherapy) 2.0a 

a

 This emission factor is the average of values ranging from 1 kg to 10 kg per kg charge, depending on model, manufacturer, and service 

intervals. 

Source: Schwarz (2005) 

Tier 3 method – user-level mass-balance method 

To calculate SF6 emissions from industrial and medical particle accelerators, use the same Tier 3 method as the 

university and research facilities. The customer service organisations for manufacturers and distributors of the 

equipment are likely to have information on equipment stocks, imports, and exports, and on the quantities of SF6

used to fill and refill the equipment. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.31 

EMISSIONS FROM OTHER APPLICATIONS OF SF6 AND PFCs 

It is good practice to contact all gas producers/distributors to identify SF6 and PFC users and to investigate the 

gas consumption of source categories other than those mentioned above. The key difference among the 

applications discussed below is the typical delay between the purchase of the SF6 or PFC and the release of the 

chemical. In some cases (e.g., SF6 used in sound-proof glazing, PFCs used as heat transfer fluids), the chemical 

is fairly well contained during the life of the equipment or product, and most emissions are associated with the 

manufacture and disposal of the product. In these cases, the delay between the purchase of the chemical and its 

final emission depends on the lifetime of the product, ranging from three years for tyres and sport-shoes to 25 

years for sound-proof glazing. In other cases (e.g., use of SF6 and PFCs as tracers or in medical applications), the 

chemical is fully emitted within a year of its purchase. If, as a result of an initial survey, applications with 

distinctive delayed emissions appear significant, then good practice is to use a source category-specific emission 

calculation, taking into account the delay in emissions. 

Adiabatic uses 

Adiabatic uses of SF6 and some PFCs exploit the low permeability of these gases through rubber. Historically, 

SF6 has been the dominant gas in these applications; however, PFCs with similar molecular weights (such as 

C3F8) have recently been used as well. Applications with a delay period of 3 years include or car tyres, sport 

shoe soles and tennis balls (Schwarz et al., 1996). For applications with emissions that are delayed by three years, 

the following formula can be used. 

EQUATION 8.19 

ADIABATIC PROPERTY APPLICATIONS

Emissions in year t = Sales in year (t – 3) 

Sound-proof glazing 

Double-glazed sound-proof windows: Approximately one-third of the total amount of SF6 purchased is released 

during assembly (i.e., filling of the double glass window) (Schwarz/Leisewitz, 1999). For the stock of gas 

remaining inside the window (capacity), an annual leakage rate of 1 percent is assumed (including glass 

breakage). Thus, about 75 percent of initial stock remains at the end of its 25-year lifetime. The application of 

SF6 in windows began in 1975, so disposal is only beginning to occur. Emissions from this source sub-category 

should be calculated using Equations 8.20 to 8.22: 

EQUATION 8.20 

DOUBLE-GLAZED WINDOWS: ASSEMBLY

Assembly Emissions in year t = 0.33 • SF6 purchased to fill windows assembled in year t 

EQUATION 8.21 

DOUBLE-GLAZED WINDOWS: USE

Leakage Emissions in year t = 0.01 • Capacity of Existing Windows in year t 

EQUATION 8.22 

DOUBLE-GLAZED WINDOWS: DISPOSAL

Disposal Emissions in year t = Amount Left in Window at End of Lifetime in year t • (1 – 

Recovery Factor) 

Unless country-specific data are available, a default recovery factor value of zero should be assumed in Equation 

8.22. If no specific information is available for these sub-source categories, good practice is to treat them as 

prompt emissions. 
Volume 3: Industrial Processes and Product Use 

8.32 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

PFCs used as heat transfer fluids in consumer and commercial applications 

PFCs are used as heat transfer fluids in a number of high-power-density commercial and consumer electronic 

applications. Commercial applications include cooling for supercomputer, telecommunication, and airport radar 

systems, as well as drive units (rectifiers) on high-speed trains (Burton, 2006). These applications consume much 

smaller volumes of liquid PFCs than electronics manufacturing, but are believed to be significant among ‘niche’ 

applications. Consumer applications include cooling kits for desktop computers that are operated at high voltages 

to increase their processing speed. The specific PFCs used in these applications are believed to be similar to 

those identified as heat transfer fluids in electronics manufacturing in Chapter 6. In all of these applications, the 

liquid PFCs are used in closed modules, indicating that most emissions occur during the manufacture, 

maintenance, and disposal of the product or equipment. Thus, if inventory compilers can acquire information on 

emission rates during the manufacture, maintenance, and disposal of the equipment, along with the quantities of 

equipment manufactured, used, and disposed each year, they can use the Tier 2 or Tier 3 method for electrical 

equipment to estimate emissions. For applications with different emissions profiles (e.g., prompt emissions), the 

appropriate equation from Section 8.2 may be used. 

PFCs used in cosmetic and medical applications 

PFCs with relatively large molecular weights (e.g., C10F18) are used in cosmetic and medical applications, 

exploiting their ability to carry oxygen to living tissue (May, 2006). Cosmetic applications include anti-wrinkle 

creams and are estimated to consume fairly small amounts. Current and potential medical applications include 

storage of pancreatic tissue for transplants (using the ‘two-layer method’), eye surgery (to repair retinal tears), 

pneumonectomy (lung therapy and diagnosis), use as a contrast agent in ultrasonic and MRI examinations, blood 

extension, wound healing, and treatment of diseases of the middle ear. All but the first two medical applications 

involve only small quantities and/or are at the research stage. Storage of pancreatic tissue is a small but growing 

application. Emissions from medical uses are uncertain but are believed to be small. 

In all of these applications, the PFC is believed to be emitted into the atmosphere within one year of its purchase. 

Thus, emissions from these sources can be estimated using Equation 8.23 for prompt emissions. 

Any other uses of SF6 and PFCs 

Other applications for SF6 and PFCs that are not specifically addressed above include their use as tracers (in leak 

detection, indoor and outdoor tracking of air-masses, and oil recovery6) and use of SF6 in the production of 

optical cables (for fluorodoping of glass fibres7). Often the gases or liquids are emitted within one year of 

purchase. In this case, good practice in calculating SF6 and PFC emissions from these ‘prompt’ emissive 

applications is to use the following formula:

EQUATION 8.23 

PROMPT EMISSIONS

Emissions in year t = (0.5 • Amount Sold in year t) + (0.5 • Amount Sold in year t – 1) 

This equation is similar to the equation for prompt ODS Substitute applications (e.g., aerosols and solvents) 

addressed in Chapter 7 of this volume. The equation covers more than one year because both sales and emissions 

are assumed to be continuous over the year; that is, chemical sold in the middle of year t-1 is not fully emitted 

until the middle of year t. 

8.3.2.2 CHOICE OF EMISSION FACTORS

For ‘other’ source categories of SF6 and PFCs that contribute substantially to a country’s SF6 and PFCs 

emissions, countries are encouraged to develop country-specific emission factors based on occasional surveys of 

representative subsets of sources. It is good practice to clearly document such emission factors. Default emission 

factors are provided above for AWACS, accelerators, prompt emissive applications and adiabatic applications, 

including windows. 

 

6

 D. Vlachogiannis et al. (2005). This paper indicated that some fraction of injected PFCs and SF6 was destroyed during fuel 

combustion, but the magnitude of this fraction (compared to the fraction of injected chemical that escaped before 

combustion) was unclear. 

7

 See further information on this application in Schwarz (2005). 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.33 

8.3.2.3 CHOICE OF ACTIVITY DATA

The activity data for these sub-source categories should be consistent with the data used in the calculation of SF6

emissions from other source categories (e.g., electrical equipment) to ensure that the estimate is complete and 

there is no double counting. For medical linear accelerators, the customer service organisations for 

manufacturers and distributors of the equipment are likely to have information on equipment stocks, imports, and 

exports, and on the quantities of SF6 used to fill and refill the equipment. Guidance regarding possible sources of 

activity data for other sources is provided under the method for each source category. 

8.3.2.4 COMPLETENESS 

Data per application on import, export and consumption from national SF6 and PFC producers and distributors 

will suffice, provided that (i) all SF6 and PFC producers and distributors are identified, (ii) domestic consumers 

only purchase SF6 and PFCs from national suppliers, and (iii) imports and exports in products (e.g., sport 

attributes) are negligible. It is good practice to check regularly for additional distributors to ensure that no gas is 

imported directly (in bulk) by end-users and that identified products containing SF6 or PFCs are not imported in 

sizeable amounts. 

Alternatively, if top-down data on chemical consumption is not available, countries may use information on the 

number of accelerators, AWACS, windows, etc. in use in the country, applying the emission factors that are 

supplied in the method for each source category. 

8.3.2.5 DEVELOPING A CONSISTENT TIME SERIES

For base year estimates, data may be needed for a few years prior to the base year; one year for prompt 

emissions and more years for delayed emission applications. It is good practice to calculate emissions using the 

same method for every year in the time series. Where data are unavailable to support a more rigorous method for 

all years in the time series, it is good practice to recalculate according to the guidance provided in Volume 1, 

Chapter 5. 

8.3.3 Uncertainty assessment 

If the survey of domestic sales per application by national gas producers and distributors is complete, then the 

accuracy of annual apparent consumption data will be high. The uncertainty in emissions estimates will be 

similarly small when the uses are all prompt emissions. In case of delayed emission applications, the 

uncertainties are: 

• Default delay times in adiabatic property applications: 3±1 year; 

• Defaults for soundproof windows: 50±10% filling emissions and 1±0.5% leakage/breach emissions. 

If gas consumption data are not available, uncertainties regarding the numbers and usage of accelerators and 

AWACS, etc. become important. 

• For accelerators, the total SF6 charge and leak rate determine emissions and associated uncertainty 

• For use of SF6 in AWACS, the number of sorties per plane has a significant impact on emissions and 

uncertainty. 

8.3.4 Quality Assurance/Quality Control (QA/QC), 

Reporting and Documentation 

8.3.4.1 QUALITY ASSURANCE/QUALITY CONTROL

It is good practice to conduct quality control checks as outlined in Volume 1, Chapter 6, and an expert review of 

the emissions estimates. Additional quality control checks as outlined in Volume 1, and quality assurance 

procedures may also be applicable, particularly if higher tier methods are used to determine emissions from this 
Volume 3: Industrial Processes and Product Use 

8.34 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

source category. Inventory compilers are encouraged to use higher tier QA/QC for key categories as identified in 

Volume 1, Chapter 4. 

Additional procedures specific to other sources of SF6 are outlined below: 

Comparison of emissions estimates using different approaches 

Inventory compilers should compare total national potential SF6 and PFC emissions (minus the amount allocated 

to the source categories as per chapters 3.10, 4, 6 and 8.2) to the estimated SF6 and PFC emissions from other 

uses. These adjusted potential national emissions can be used as an upper bound on emissions. 

Activity data check 

Inventory compilers should compare the activity data submitted by different producers and distributors, and, 

adjusting for relative size or capacity of the companies, identify significant outliers. Any outliers should be 

investigated to determine if the differences can be explained or if there is an error in the reported activity. 

Comparison of emission rates with those of other countries 

Inventory compilers should compare the emissions from other SF6 and PFC end-uses included in the national 

inventory with information submitted by other similar countries. For each source, emissions per capita or per 

unit of GDP should be compared with the corresponding emission rates of other countries. If national figures 

appear to be relatively very high or very small, a justification should be provided. 

8.3.4.2 REPORTING AND DOCUMENTATION

It is good practice to document and archive all information required to produce the national emissions inventory 

estimates as outlined in Volume 1, Section 6.11. It is not practical to include all documentation in the national 

inventory report. However, the inventory should include summaries of methods used and references to source 

data such that the reported emissions estimates are transparent and steps in their calculation may be retraced. 

For transparency, it is good practice to report both actual and potential emissions from the source category ‘other 

uses’ separately from other SF6 and PFC emissions. In addition, providing information on the specific 

applications that are included in this source category is useful for comparing (estimates of) national practices 

with other countries, regionally, or globally. In addition, the methods applied and references should be 

documented. For delayed emission sub-source categories, annual emissions, delay times and emission factors per 

type of sub-source category should be reported. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.35 

8.4 N2O FROM PRODUCT USES 

8.4.1 Introduction 

Evaporative emissions of nitrous oxide (N2O) can arise from various types of product use, including: 

• Medical applications (anaesthetic use, analgesic use and veterinary use); 

• Use as a propellant in aerosol products, primarily in food industry (pressure-packaged whipped cream, etc); 

• Oxidising agent and etchant used in semiconductor manufacturing; 

• Oxidising agent used, with acetylene, in atomic absorption spectrometry; 

• Production of sodium azide, which is used to inflate airbags; 

• Fuel oxidant in auto racing; and 

• Oxidising agent in blowtorches used by jewelers and others. 

In general, medical applications and use as a propellant in aerosol products are likely to be larger sources than 

others. It is good practice to estimate and report N2O emissions from these sources. Inventory compilers are 

encouraged to estimate and report N2O emissions from the other sources as well, if data are available. 

MEDICAL APPLICATIONS 

Anaesthetic use of N2O 

N2O for anaesthetic use is supplied in steel cylinders containing a minimum of 98 percent N2O. N2O is used 

during anaesthesia for two reasons: a) as an anaesthetic and analgesic and as b) a carrier gas for volatile 

fluorinated hydrocarbon anaesthetics such as isoflurane, sevoflurane and desflurane. The anaesthetic effect of 

N2O is additive to that of the fluorinated hydrocarbon agents. 

Not all anaesthetics require the use of N2O, and the use of N2O is contra-indicated in a small number of medical 

situations. The carrier gas during anaesthesia may be either N2O and oxygen or a mixture of air and oxygen, in 

which case N2O is avoided. 

Inhaled anaesthetic agents are increasingly administered via breathing systems which re-circulate the exhaled 

breath of the patient through a canister of carbon dioxide absorbent before directing the gases back to the patient. 

Using this method the flow of carrier gas can be reduced considerably after the first few minutes of anaesthesia 

when uptake by the patient is high. This technique is known as Low Flow Anaesthesia. Low Flow Anaesthesia 

has the advantage of reducing emissions as well as reducing cost. 

Some anaesthetics may avoid both N2O and the fluorinated hydrocarbon agents completely by employing a 

technique in which an anaesthetic drug is continuously infused into a vein throughout the surgical procedure. 

This technique is known as Total Intravenous Anaesthesia. 

Analgesic use of N2O 

Inhaled N2O is used to provide pain relief in certain situations. For example, it is supplied in steel cylinders 

containing pre-mixed N2O 50 percent and oxygen 50 percent as premixed nitrous oxide and oxygen mixtures in 

the UK. Premixed nitrous oxide and oxygen mixtures are used to provide pain relief in childbirth, and for painful 

procedures of short duration, e.g. for dressings to be changed in burns patients. Premixed nitrous oxide and 

oxygen mixtures are not used in countries with a very cold climate because the mixture can separate if the 

cylinders are stored below –6 degrees centigrade, with the consequent risk of administering pure nitrous oxide to 

patients with no oxygen. 

Veterinary use of N2O 

N2O is also used during animal anaesthesia. Administration methods are similar to those used in human 

anaesthesia. 
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8.36 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

USE AS A PROPELLANT IN AEROSOL PRODUCTS, PRIMARILY IN FOOD 

INDUSTRY 

N2O is also used as a propellant in aerosol products primarily in food industry. Typical usage is to make whipped 

cream, where cartridges filled with N2O are used to blow the cream into foam. 

8.4.2 Methodological issues 

8.4.2.1 CHOICE OF METHOD

It is good practice to estimate N2O emissions from data of quantity of N2O supplied that are obtained from 

manufacturers and distributors of N2O products according to Equation 8.24 below. There will be a time delay 

between manufacture, delivery and use but this is probably small in the case of medical applications because 

hospitals normally receive frequent deliveries to avoid maintaining large stores. Therefore, it is reasonable to 

assume that the N2O products supplied will be used in one year. In the case of use as a propellant in aerosol 

products, there is no reliable data that prove there is a significant time delay between manufacture, delivery and 

use. Such being the case, it is considered practical to assume that the N2O products supplied will be used in one 

year. Equation 8.24 covers more than one year because both supply and use are assumed to be continuous over 

the year; that is, N2O supplied in the middle of year t–1 is not fully used and emitted until the middle of year t. 

Different tiers could not be defined for this source category, because there is no other reliable estimation method. 

For example, in the case of medical applications, estimations from numbers of anaesthetics given, number of 

surgical beds or hours of anaesthesia could be considered but these methods are likely to be inaccurate. (See 

Section 8.4.2.3, Choice of Activity Data.) 

EQUATION 8.24 

N2O EMISSIONS FROM OTHER PRODUCT USES

= ∑{ [ • + • − ]• }

i

N O i i EFi E (t) 0.5 A (t) 0.5 A (t 1) 2

Where: 

EN2O(t) = emissions of N2O in year t, tonnes 

Ai (t) = total quantity of N2O supplied in year t in application type i, tonnes 

Ai (t-1) = total quantity of N2O supplied in year t-1 in application type i, tonnes 

EFi = emission factor for application type i, fraction 

8.4.2.2 CHOICE OF EMISSION FACTORS

MEDICAL APPLICATIONS 

It is assumed that none of the administered N2O is chemically changed by the body, and all is returned to the 

atmosphere. It is reasonable to assume an emission factor of 1.0. 

USE AS A PROPELLANT IN AEROSOL PRODUCTS, PRIMARILY IN FOOD 

INDUSTRY 

For N2O used as a propellant in pressurized and aerosol food products, none of the N2O is reacted during the 

process and all of the N2O is emitted to the atmosphere resulting in an emissions factor of 1.0 for this source. 

OTHERS 

For the other types of product use, it may not be appropriate to assume an emissions factor of 1.0. In case the 

inventory compilers estimate and report N2O emissions arising from product use other than medical applications 

and use as a propellant in aerosol products, they are encouraged to derive reasonable emission factors for that 

source from literature or measurements. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.37 

8.4.2.3 CHOICE OF ACTIVITY DATA

MEDICAL APPLICATIONS 

Total quantity of N2O supplied by application type should be obtained from manufacturers and distributors of 

N2O products. Alternatively, for medical applications, quantity of N2O usage may be obtained from the 

pharmacy department in individual hospitals that usually have records of the number and capacity of nitrous 

oxide cylinders purchased per annum. 

The duration of hospital stay following a surgical procedure varies considerably from less than one day to 

several days or weeks. Estimates of the number of anaesthetics administered which are calculated from the 

surgical bed occupancy are likely to be inaccurate. 

Because N2O is used in only a proportion of anaesthetics its use cannot be estimated reliably from the number of 

anaesthetics given. 

The flow of N2O (L/min) delivered by the anaesthetic apparatus may be varied by the anaesthetist during the 

course of surgery, typically between zero and 6 L/min. Because of this considerable variability, estimates of 

consumption based on duration of anaesthesia are likely to be inaccurate. 

The proportion of anaesthetics in which N2O is used varies between countries and between individual 

anaesthetists in a given country. Over the recent years there appears to be a general reduction in the proportion of 

anaesthetics which incorporate N2O but data are sparse. 

USE AS A PROPELLANT IN AEROSOL PRODUCTS, PRIMARILY IN FOOD 

INDUSTRY 

Total quantity of N2O supplied by application type should be obtained from manufacturers and distributors of 

N2O products. 

8.4.2.4 COMPLETENESS

Data per application on import, export and consumption from national N2O manufacturers and distributors will 

suffice, provided that (i) all N2O manufacturers and distributors are identified, (ii) domestic consumers only 

purchase N2O from national suppliers, and (iii) imports and exports in products (e.g. sport attributes) are 

negligible. It is good practice to check regularly for additional distributors to ensure that no N2O is imported 

directly (in bulk) by end users and that identified products containing N2O are not imported in sizeable amounts. 

8.4.2.5 DEVELOPING A CONSISTENT TIME SERIES

It is good practice to calculate emissions of N2O using the same method for every year in the time series. Where 

data are unavailable to support a more rigorous method for all years in the time series, it is good practice to 

recalculate according to the guidance provided in Volume 1, Chapter 5. 

8.4.3 Uncertainty assessment 

8.4.3.1 EMISSION FACTOR UNCERTAINTIES

In the published literature it is widely assumed that none of the N2O inhaled by a patient during anaesthesia is 

metabolised. N2O is taken up continuously from the lungs as dissolved N2O in blood. The portion which is not 

taken up is exhaled in the next breath. Uptake by the patient is high initially and falls progressively in a nearexponential fashion over time. It is reasonable to assume that all the administered N2O is eventually returned to 

the atmosphere and the emission factor is 1.0. This is a pragmatic assumption because there are no reliable data. 

Any error in the emission factor is likely to be extremely small in comparison with other uncertainties. 

Also in the case of use as a propellant in aerosol products, N2O is not likely to be reacted during the process. 

Therefore, it is a pragmatic assumption that emission factor is 1.0, and any error in the emission factor is likely 

to be extremely small in comparison with other uncertainties. 
Volume 3: Industrial Processes and Product Use 

8.38 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

In case the inventory compilers estimate and report N2O emissions arising from product use other than medical 

applications and use as a propellant in aerosol products, emission factor uncertainties may need to be carefully 

considered. 

8.4.3.2 ACTIVITY DATA UNCERTAINTIES

The uncertainties in quantity of N2O supplied by application type obtained from manufacturers and distributors 

of N2O products may vary widely from country to country. If the uncertainty estimates are obtainable from the 

manufacturers and distributors, those estimates should be used. Otherwise, activity data uncertainties should be 

estimated by expert judgement. 

8.4.4 Quality Assurance/Quality Control (QA/QC), 

Reporting and Documentation 

It is good practice to document and archive all information required to produce the national emissions inventory 

estimates as outlined in Volume 1, Chapter 6. It is not practical to include all documentation in the national 

inventory report. However, the inventory should include summaries of methods used and references to source 

data such that the reported emissions estimates are transparent and steps in their calculation may be retraced. 

For transparency, providing information on the specific applications that are included in this source category is 

useful for comparing (estimates of) national practices with other countries, regionally, or globally. In addition, 

the methods applied and references should be documented. 

It is good practice to conduct quality control checks and quality assurance procedures as outlined in Volume 1, 

Chapter 6. Inventory compilers are encouraged to use higher tier QA/QC for key categories as identified in 

Volume 1, Chapter 4. 

Additional procedures specific to this source category are outlined below: 

Activity data check 

Inventory compilers should compare the activity data submitted by different manufacturers and distributors of 

N2O, and, adjusting for relative size or capacity of the companies, to identify significant outliers. Any outliers 

should be investigated to determine if the differences can be explained or if there is an error in the reported 

activity. 

Comparison of emissions with other countries 

Inventory compilers should compare the N2O emissions from types of product use included in the national 

inventory with information submitted by other similar countries. For each source, emissions per capita or per 

unit of GDP with other countries should be compared. If national figures appear to be relatively very high or 

very small, a justification should be provided. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.39 

References 

SECTIONS 8.1 - 8.3 

Aoyama, T. (2004). Japan Electrical Manufacturers’ Association (JEMA), “The Situation of Reduction in SF6

Emissions from Gas-insulated Electrical Equipment In Japan” Paper and presentation delivered to the 

Conference on SF6 and the Environment, Scottsdale, Arizona, December 1-3, 2004. 

AREVA (2005). AREVA, World energy experts, Activity and Sustainable Development Report 2004. 

(Registered office: rue Le Peletier – 75009 Paris – France, http://www.areva.com/), published in July 

2005. 

Boeing (2005). “E-3 AWACS in Service Worldwide”, March 2005. Boeing Integrated Defense Systems, P.O. 

Box 516, St. Louis, MO 63166, (Available from http://www.boeing.com/defense-space/ic/awacs/docs/E3AWACS_overview.pdf) 

Burton, C. S. (2006). “Uses and Air Emissions of Liquid PFC Heat Transfer Fluids from the Electronics Sector,” 

Report prepared for Scott C. Bartos, U.S. Environmental Protection Agency. 

Ecofys (2005). Reductions of SF6 Emissions from High and Medium Voltage Electrical Equipment in Europe, Final Report 

to CAPIEL, S, Wartmann and J. Harnisch, June 28, 2005 

FEPC and JEMA (2004). Federation of Electric Power Companies (FEPC) and the Japan Electrical 

Manufacturers’ Association (JEMA), “Japanese Emission Factors.” (Personal communication from Mr. 

Kiyoshi Saitoh of Japan Electrical Manufacturers Association (JEMA) to Mr. Kiyoto Tanabe, IPCC 

Technical Support Unit, November, 2004.) 

Harris, D., and Hildebrandt, J. (2003). “Spray Cooling Electrical and Electronic Equipment,” COTS Journal, 

November 2003. 

CIGRE (2005). International Council on Large Electric Systems (CIGRE) Publication No.276: Guide for the 

Preparation of customized “Practical SF6 Handling Instructions”, Task Force B3.02.01, August 2005. 

IEC (1996). International Electro-technical Commission (IEC) Standard 60694: “Common specifications for 

high-voltage switchgear and controlgear standards,” Second edition, 1996-05. Geneva, Switzerland. 

Koch, E.C. (2004). “Special Materials in Pyrotechnics: III. Application of Lithium and its Compounds in 

Energetic Systems;” Propellants, Explosives, Pyrotechnics, Volume 29, Issue 2, Pages 67 - 80, 2004 

May, G. (2006). F2 Chemicals Limited. Personal communication with Deborah Ottinger Schaefer, January 23, 

2006. 

Maruyama, S. and Meguro, M. (2000). “SF6 Gas Emission Reduction From Gas-Insulated Electrical Equipment 

in Japan.”, Paper presented at the Conference on SF6 and the Environment: Emission Reduction 

Strategies in San Diego, USA (November 2000). 

NIST (1997). Gases for Electrical Insulation and Arc Interruption: Possible Present and Future Alternatives to 

Pure SF6; by L. G. Christophorou, J. K. Olthoff, D. S. Green; NIST Technical Note 1425, National 

Institute of Standards, November 1997. 

Schwarz, W. and Leisewitz, A. (1996). Current and future emissions of fluorinated compounds with global 

warming effect in Germany (in German). Report UBA-FB 1060 1074/01, Umweltbundesamt, Berlin. 

Schwarz, W. and Leisewitz, A. (1999). Emissions and reduction potentials of HFCs, PFCs, and SF6 in Germany. 

Report UBA-FB 298 41 256, Umweltbundesamt, Berlin. 

Schwarz, W. (2005). Emissions, Activity Data, and Emission Factors of Fluorinated Greenhouse Gases (F-Gases) 

in Germany 1995-2002. Research Report 201 41 261/01, UBA-FB 000811/e, Umweltbundesamt, Berlin. 

Schwarz, W. (2006). “The German Monitoring System for SF6 Emissions from Equipment for Electricity 

Transmission and Distribution.” 

Smythe, K. (2004). ‘Trends in SF6 Sales and End-Use Applications: 1961-2003.’ International Conference on 

SF6 and the Environment: Emission Reduction Technologies, December 1-3, 2004, Scottsdale, AZ. 

U.S. EPA (2004). U.S. Inventory of Greenhouse Gases and Sinks, 1990-2002. U.S. Environmental Protection 

Agency, April, 2004. 

Vlachogiannis, D., et al. (2005). Assessment of the impact of SF6 and PFCs reservoir tracers on global warming, 

the AEOLOS study, Non-CO2 Greenhouse Gases (NCGG-4), coordinated by A. van Amstel, Rotterdam, 

p. 389-396. 
Volume 3: Industrial Processes and Product Use 

8.40 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

SECTION 8.4 

Austria [Umweltbundesamt] (2004), AUSTRIA’S NATIONAL INVENTORY REPORT 2004, Submission 

under the United Nations Framework Convention on Climate Change 

Beatty PCW, Kay B and Healy TEJ (1984), Measurement of the rates of nitrous oxide uptake and nitrogen 

excretion in man. British Journal of Anaesthesia; 56: 223-232. 

Environment Canada (2004), Canada’s Greenhouse Gas Inventory 1990-2002 

Jordan M. (1996), Pharmacology in the Practice of Anaesthesia p 43. Arold, London. Edited by Kaufman L and 

Tabener PV. 

U.S. EPA (2004). U.S. Inventory of Greenhouse Gases and Sinks, 1990-2002. U.S. Environmental Protection 

Agency, April, 2004. 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.41 

Annex 8A Examples of Tier 3 national SF6 inventory 

systems 

Figures 8A.1 and 8A.2 illustrate the Tier 3 Hybrid approach as it is currently applied in Germany for closed 

pressure (high voltage) and sealed-pressure (medium voltage) equipment (Schwarz, 2006). In the diagram, ‘MB’ 

indicates processes or life cycle stages for which the mass-balance approach is used, while ‘EF’ indicates 

processes and life cycle stages for which emission factors are used. For example, in manufacturing, the massbalance approach is used to estimate emissions from the filling of gas-insulated switchgear, while emission 

factors are used to estimate emissions from the filling of bushings, instrument transformers, and circuit breakers. 

In Germany, the latter processes have emission rates of 1 percent or less, making emissions difficult to measure 

using mass-balance methods. Note that this diagram is intended to be an example only; when implementing the 

Tier 3 approach, countries are encouraged to choose approaches and emission factors appropriate to their 

national circumstances. 
Volume 3: Industrial Processes and Product Use 

8.42 2006 IPCC Guidelines for National Greenhouse Gas Inventories 

Figure 8A.1 Example of Tier 3 approach: Germany, High-Voltage equipment 

Legend for Emissions Estimation in HV 

Mass Balance Approach 

Symbol Equation 

MB I Development Emissions = Consumption for Developing minus Return from Development Department 

MB II GIS Charging Emissions = Consumption for Charging minus Charge (nameplate capacities); also applicable to Gas 

insulated Lines (GIL’s) 

MB III Operating Emissions I = Annually surveyed topping up by equipment operators 

MB IV Operating Emissions II = Nameplate capacity of decommissioned equipment minus gas recovered from this equipment 

Emission Factor (EF) Approach 

Symbol Kind of Emission Factor (EF) Multiplied by 

EF 1 Factory Filling EF Bushings* NC** of bushings filled in factory 

EF 2 Factory Filling EF Outdoor Instrument Transformers (ITs) NC of ITs filled in factory 

EF 3 Factory Filling EF Gas Circuit Breakers (GCBs) NC of GCBs filled in factory 

EF 4 Site Erection EF GIS and GIL NC of GIS and GIL filled on site 

EF 5 Site Erection EF GCBs NC of GCBs filled on site 

EF 6 Site Erection EF Outdoor ITs NC of Outdoor ITs filled on site 

EF 7 Disposal EF NC of decommissioned equipment 

* Bushings are treated as integral parts of GIS as of Site erection. 

**NC = Total nameplate capacity of equipment undergoing a given process 
Chapter 8: Other Product Manufacture and Use 

2006 IPCC Guidelines for National Greenhouse Gas Inventories 8.43 

Figure 8A.2 Example of Tier 3 approach: Germany, Medium-Voltage equipment 

Legend for Emissions Estimation in MV 

Mass Balance Approach 

Symbol Equation 

MB I Development Emissions = Consumption for Developing minus Return from Development Department* 

Emission Factor (EF) Approach 

Symbol Kind of Emission Factor (EF) Multiplied by 

EF 1 Factory Filling EF NC** filled in factory 

EF 2 Site Erection EF NC*** filled on site 

EF 3 Operating EF NC of operating equipment (total bank from this and previous years) 

EF 4 Disposal EF NC decommissioned 

* This mass balance approach also applies to manufacturing of Cast Resin Instrument Transformers (ITs). 

**NC = Total nameplate capacity of equipment undergoing a given process. 

*** In countries where MV equipment is already gas-filled in factories, site erection emissions are negligible.