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5.0 PNEUMATIC CONTROLLERS

The natural gas industry uses a variety of process control devices to operate valves that regulate 

pressure, flow, temperature, and liquid levels. Most instrumentation and control equipment falls into one 

of three categories: (1) pneumatic; (2) electrical; or (3) mechanical. Of these, only pneumatic devices are 

direct sources of air emissions. Pneumatic controllers are used throughout the oil and natural gas sector 

as part of the instrumentation to control the position of valves. This chapter describes pneumatic devices 

including their function and associated emissions. Options available to reduce emissions from pneumatic 

devices are presented, along with costs, emission reductions, and secondary impacts. Finally, this 

chapter discusses considerations in developing regulatory alternatives for pneumatic devices.

5.1 Process Description

For the purpose of this document, a pneumatic controller is a device that uses natural gas to transmit a 

process signal or condition pneumatically and that may also adjust a valve position based on that signal, 

with the same bleed gas and/or a supplemental supply of power gas. In the vast majority of applications,

the natural gas industry uses pneumatic controllers that make use of readily available high-pressure 

natural gas to provide the required energy and control signals. In the production segment, an estimated 

400,000 pneumatic devices control and monitor gas and liquid flows and levels in dehydrators and 

separators, temperature in dehydrator regenerators, and pressure in flash tanks. There are around 

13,000 gas pneumatic controllers located in the gathering, boosting and processing segment that control 

and monitor temperature, liquid, and pressure levels. In the transmission segment, an estimated 

85,000 pneumatic controllers actuate isolation valves and regulate gas flow and pressure at compressor 

stations, pipelines, and storage facilities. 

Pneumatic controllers are automated instruments used for maintaining a process condition such as liquid 

level, pressure, pressure differential, and temperature. In many situations across all segments of the oil 

and gas industry, pneumatic controllers make use of the available high-pressure natural gas to operate

control of a valve. In these “gas-driven” pneumatic controllers, natural gas may be released with every 

valve movement and/or continuously from the valve control pilot. The rate at which the continuous 

release occurs is referred to as the bleed rate. Bleed rates are dependent on the design and operating 

characteristics of the device. Similar designs will have similar steady-state rates when operated under 

similar conditions. There are three basic designs: (1) continuous bleed devices are used to modulate 

flow, liquid level, or pressure, and gas is vented continuously at a rate that may vary over time; (2) snap-
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acting devices release gas only when they open or close a valve or as they throttle the gas flow; and (3) 

self-contained devices release gas to a downstream pipeline instead of to the atmosphere. This analysis 

assumes self-contained devices that release natural gas to a downstream pipeline instead of to the 

atmosphere have no emissions are not further discussed in this analysis.

Bleeding pneumatic controllers can be classified into two types based on their emissions rates: (1) highbleed controllers and (2) low-bleed controllers. A controller is considered to be high-bleed when the 

continuous bleed emissions are in excess of 6 standard cubic feet per hour (scfh), while low-bleed 

devices bleed at a rate less than or equal to 6 scfh.a

Snap-acting controllers are devices that only emit gas during actuation and do not have a continuous 

bleed rate. The actual amount of emissions from snap-acting devices is dependent on the amount of 

natural gas vented per actuation and how often it is actuated. Bleed devices also vent an additional 

volume of gas during actuation, in addition to the device‟s bleed stream. Since actuation emissions serve 

the device‟s functional purpose and can be highly variable, the emissions characterized for high-bleed 

and low-bleed devices in this analysis (as described in section 5.2.2) account for only the continuous 

flow of emissions (i.e. the bleed rate) and do not include emissions directly resulting from actuation. 

Snap-acting controllers are assumed to have zero bleed emissions. Most applications (but not all), snapacting devices serve functionally different purposes than bleed devices. Therefore, snap-acting 

controllers are not further discussed in this analysis. 

In addition, not all pneumatic controllers are gas driven. These “non-gas driven” pneumatic controllers 

use sources of power other than pressurized natural gas, such as compressed “instrument air.” Because 

these devices are not gas driven, they do not directly release natural gas or VOC emissions, but they do 

have energy impacts, with associated secondary impacts related to generation of the electrical power 

required to drive the instrument air compressor system. These non-gas driven pneumatic devices are 

feasible only at oil and gas locations where the devices can be driven by compressed instrument air 

systems and have electrical service sufficient to power an air compressor. At sites without electrical 

service sufficient to power an instrument air compressor, only gas driven pneumatic devices can be 

used. This analysis assumes that natural gas processing plants are the only facilities in the oil and gas 

 

a The classification of high-bleed and low-bleed devices originated from a report by Pacific Gas & Electric (PG&E) and the 

Gas Research Institute (GRI) in 1990 titled “Unaccounted for Gas Project Summary Volume”. This classification was 

adopted for the October 1993 Report to Congress titled “Opportunities to Reduce Anthropogenic Methane Emissions in the 

United States”. As described on page 2-16 of the report, “devices with emissions or „bleed‟ rates of 0.1 to 0.5 cubic feet per 

minute are considered to be „high-bleed‟ types (PG&E 1990).” This range of bleed rates is equivalent to 6 to 30 cubic feet per 

hour.
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sector highly likely to have electrical service sufficient to power an instrument air system, and that most 

existing gas processing plants use instrument air instead of gas driven devices.7The application of 

electrical controls is further elaborated in Section 5.3.

5.2 Emissions Data and Information

5.2.1 Summary of Major Studies and Emissions

In the evaluation of the emissions from pneumatic devices and the potential options available to reduce 

these emissions, numerous studies were consulted. Table 5-1 lists these references with an indication of 

the type of relevant information contained in each study.

5.2.2 Representative Pneumatic Device Emissions

For this analysis, EPA consulted information in the appendices of the Natural Gas STAR Lessons 

Learned document on pneumatic devices,

11 Subpart W of the Greenhouse Gas Reporting rule, as well as 

obtained updated data from major vendors of pneumatic devices. The data obtained from vendors 

included emission rates, costs, and any other pertinent information for each pneumatic device model (or 

model family). All pneumatic devices that a vendor offered were itemized and inquiries were made into 

the specifications of each device and whether it was applicable to oil and natural gas operations. Highbleed and low-bleed devices were differentiated using the 6 scfh threshold. 

Although by definition, a low-bleed device can emit up to 6 scfh, through this vendor research, it was 

determined that the typical low-bleed device available currently on the market emits lower than the 

maximum rate allocated for the device type. Specifically, low-bleed devices on the market today have 

emissions from 0.2 scfh up to 5 scfh. Similarly, the available bleed rates for a high bleed device vary 

significantly from venting as low as 7 scfh to as high as 100 scfh.1,b While the vendor data provides 

useful information on specific makes and models, it did not yield sufficient information about the 

prevalence of each make and model in the population of devices which is an important factor in 

developing a representative emission factor. 

 

b All rates are listed at an assumed pressure supply of 20 psig.
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Table 5-1. Major Studies Reviewed for Consideration

of Emissions and Activity Data

Report Name Affiliation Year of 

Report

Number of

Devices

Emissions 

Information

Control 

Information

Greenhouse Gas Mandatory 

Reporting Rule and Technical 

Supporting Document 1

EPA 2010 Nationwide X

Inventory of Greenhouse Gas 

Emissions and Sinks: 1990-2009 2, 3 EPA 2011 Nationwide/Regional X

Methane Emissions from the 

Natural Gas Industry 4, 5, 6, 7

Gas Research 

Institute / 

EPA

1996 Nationwide X

Methane Emissions from the 

Petroleum Industry (draft) 8 EPA 1996 Nationwide X

Methane Emissions from the 

Petroleum Industry 9 EPA 1999 Nationwide X

Oil and Gas Emission Inventories 

for Western States 10

Western 

Regional Air 

Partnership 

2005 Regional X

Natural Gas STAR Program11 EPA 2000-

2010 X X
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Therefore, for this analysis, EPA determined that best available emissions estimates for pneumatic 

devices are presented in Table W-1A and W-1B of the Greenhouse Gas Mandatory Reporting Rule for 

the Oil and Natural Gas Industry (Subpart W). However, for the natural gas processing segment, a more 

conservative approach was assumed since it has been determined that natural gas processing plants

would have sufficient electrical service to upgrade to non-gas driven controls.

c

Therefore, to quantify 

representative emissions from a bleed-device in the natural gas processing segment, information from 

the EPA/GRI reportd was used to estimate the methane emissions from a single pneumatic device by 

type. Further distinction between high and low bleed could not be determined based on available data.

The basic approach used for this analysis was to first approximate methane emissions from the average 

pneumatic device type in each industry segment and then estimate VOC and hazardous air pollutants 

(HAP) using a representative gas composition.

12 The specific ratios from the gas composition were 

0.278 pounds VOC per pound methane and 0.0105 pounds HAP per pound methane in the production 

and processing segments, and 0.0277 pounds VOC per pound methane and 0.0008 pounds HAP per 

pound methane in the transmission segment.

Table 5-2 summarizes the estimated bleed emissions for a representative pneumatic controller by 

industry segment and device type. The volume of gas emitted during actuation is not quantified in this 

analysis; therefore to be consistent with the comparison in emissions from the bleed devices, the bleed 

emissions from snap-acting devices is estimated in this analysis as zero. 

5.3 Nationwide Emissions from New Sources

5.3.1 Approach

Nationwide emissions from newly installed natural gas pneumatic devices for a typical year were 

calculated by estimating the number of pneumatic devices installed in a typical year and multiplying by

the estimated annual emissions per device listed in Table 5-2. The number of new pneumatic devices 

installed for a typical year was determined for each segment of the industry including natural gas 

production, natural gas processing, natural gas transmission and storage, and oil production. The 

methodologies that determined the estimated number of new devices installed in a typical year is 

provided in section 5.3.2.

 

c EPA‟s approach taken for subpart W also assumed existing natural gas processing plants do not have bleed devices so no 

emission factor was developed for this segment. . 

d Table 4-11. page 56. epa.gov/gasstar/tools/related.html
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Table 5-2. Average Bleed Emission Estimates per Pneumatic Device in the Oil and Natural 

Gas Sector (tons/year)*

Industry Segment

High-Bleed Low-Bleed

Methane VOC HAP Methane VOC HAP

Natural Gas Production‡

6.91 1.92 0.073 0.26 0.072 0.003

Natural Gas Transmission and Storage‡‡ 3.20 0.089 0.003 0.24 0.007 0.0002

Oil Production±

6.91 1.92 0.073 0.26 0.072 0.003

Natural Gas Processing±± 1.00 0.28 0.01 1.00 0.28 0.01

*The conversion factor used in this analysis is 1 thousand cubic feet of methane (Mcf) is equal to 0.0208 

tons methane. Minor discrepancies may be due to rounding. 

‡Natural Gas Production methane emissions are derived from Table W-1A and W-1B of Subpart W. 

‡‡Natural gas transmission and storage methane emissions are derived from Table W-3 of Subpart W.

±Oil production methane emissions are derived from Table W-1A and W-1B of Subpart W. It is 

assumed only continuous bleed devices are used in oil production.

±±Natural gas processing sector methane emissions are derived from Volume 12 of the 1996 GRI 

report.7 Emissions from devices in the processing sector were determined based on data available for 

snap-acting and bleed devices, further distinction between high and low bleed could not be determined 

based on available data.
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5.3.2 Population of Devices Installed Annually

In order to estimate the average number of pneumatic devices installed in a typical year, each industry 

segment was analyzed separately using the best data available for each segment. For the natural gas 

production and oil production segments, the number of new pneumatics installed in a typical year was 

derived using a multiphase analysis. First, data from the US Greenhouse Gas Inventory: Emission and 

Sinks 1990-2009 was used to establish the ratio of pneumatic controllers installed per well site on a 

regional basis. These ratios were then applied to the number of well completions estimated in Chapter 4 

for natural gas well completions with hydraulic fracturing, natural gas well completions without 

hydraulic fracturing and for oil well completions. On average, one pneumatic device was assumed to be 

installed per well completion for a total of 33,411 pneumatic devices. By applying the estimated 51 

percent of bleed devices (versus snap acting controllers), it is estimated that an average of 17,040 bleeddevices would be installed in the production segment in a typical year.

The number of pneumatic controllers installed in the transmission segment was approximated using the 

Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009. The number of new devices 

installed in a given year was estimated by subtracting the prior year (e.g. 2007) from the given year‟s 

total (e.g. 2008). This difference was assumed to be the number of new devices installed in the latter 

year (e.g. Number of new devices installed during 2008 = Pneumatics in 2008 – Pneumatics in 2007). A 

3-year average was calculated based on the number of new devices installed in 2006 through 2008 in 

order to determine the average number of new devices installed in a typical year. 

Once the population counts for the number of pneumatics in each segment were established, this 

population count was further refined to account for the number of snap-acting devices that would be 

installed versus a bleed device. This estimate of the percent of snap-acting and bleed devices was based 

on raw data found in the GRI study, where 51 percent of the pneumatic controllers are bleed devices in 

the production segment, and 32 percent of the pneumatic controllers are bleed devices in the 

transmission segment.7 The distinction between the number of high-bleed and low-bleed devices was 

not estimated because this analysis assumes it is possible to predict or ensure where low bleeds will be 

used in the future. Table 5-3 summarizes the estimated number of new devices installed per year.
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Table 5-3. Estimated Number of Pneumatic Devices Installed in an Typical Year

Industry Segment Number of New Devices Estimated for a Typical Year*

Snap-Acting Bleed-Devices Total

Natural Gas and Oil Production** 16,371 17,040 33,411

Natural Gas Transmission and 

Storage‡ 178 84 262

*National averages of population counts from the Inventory were refined to include the difference in 

snap-acting and bleed devices based on raw data found in the GRI/EPA study. This is based on the 

assumption that 51 percent of the pneumatic controllers are bleed devices in the production segment, 

while 32 percent are bleed devices in the transmission segment. 

**The number of pneumatics was derived from a multiphase analysis. Data from the US Greenhouse 

Gas Inventory: Emission and Sinks 1990-2009 was used to establish the number of pneumatics per well 

on a regional basis. These ratios were applied to the number of well completions estimated in Chapter 4 

for natural gas wells with hydraulic fracturing, natural gas wells without hydraulic fracturing and for oil 

wells. 

‡The number of pneumatics estimated for the transmission segment was approximated from comparing 

a 3 year average of new devices installed in 2006 through 2008 in order to establish an average number 

of pneumatics being installed in this industry segment in a typical year. This analysis was performed 

using the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2009.
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For the natural gas processing segment, this analysis assumes that existing natural gas plants have 

already replaced pneumatic controllers with other types of controls (i.e. an instrument air system) and 

any remaining high-bleed devices that remain are safety related. As a result, the number of new 

pneumatic bleed devices installed at existing natural gas processing plants was estimated as negligible.

A new greenfield natural gas processing plant would require multiple control loops. Chapter 8 in section 

3.2.3 describes the number of natural gas processing facilities that are estimated for equipment leak 

detection. It is assumed that half of these facilities are new sites, or about 15 new processing sites. 

5.3.3 Emission Estimates

Nationwide baseline emission estimates for pneumatic devices for new sources in a typical year are 

summarized in Table 5-4 by industry segment and device type. Since the number of low-bleed versus 

high-bleed could not be determined, it was assumed for the nationwide emission estimate that all bleeddevices have the high-bleed emission rates estimated in Table 5-2 per industry segment. 

5.4 Control Techniques

Although pneumatic devices have relatively small emissions individually, due to the large population of 

these devices installed on an annual basis, the cumulative VOC emissions for the industry is significant. 

As a result, several options to reduce emissions have been developed over the years. Table 5-5 provides 

a summary of these options for reducing emissions from pneumatic devices including: instrument air, 

non-gas driven controls, and enhanced maintenance. 

Given the various control options and applicability issues, the replacement of a high-bleed with a lowbleed device is the most likely scenario for reducing emissions from pneumatic device emissions. Lowbleed devices are further described in the following section, along with estimates of the impacts of their 

application for a representative device and nationwide basis. Although snap-acting devices have zero 

bleed emissions, this analysis assumes the devices are not always used in the same functional application 

as bleed devices and are, therefore, not an appropriate form of control for all bleed devices. It is assumed 

snap-acting, or no-bleed, devices meet the definition of a low-bleed. This concept is further detailed in 

Section 5.5 of this chapter. Since this analysis has assumed areas with electrical power have already 

converted applicable pneumatic devices to instrument air systems, instrument air systems are also

described for natural gas processing plants only. Given applicability, efficiency and the expected costs 
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Table 5-4. Nationwide Baseline Emissions from Representative Pneumatic Device Installed 

in a Typical Year for the Oil and Natural Gas Industry (tons/year)*

Industry Segment

Baseline Emissions from 

Representative New Unit 

(tpy)

Number of 

New Bleed 

Devices 

Expected 

Per Year

Nationwide Baseline 

Emissions from Bleeding 

Pneumatic (tpy)**

VOC Methane HAP VOC Methane HAP

Oil and Gas 

Production 1.92 6.91 0.073 17,040 32,739 117,766 1,237

Natural Gas 

Transmission and 

Storage

0.089 3.20 0.003 84 8 288 0.2

*Emissions have been based on the bleed rates for a high-bleed device by industry segment. Minor 

discrepancies may be due to rounding.

**To estimate VOC and HAP, weight ratios were developed based on methane emissions per device. 

The specific ratios used were 0.278 pounds VOC per pound methane and 0.0105 pounds HAP per pound 

methane in the production and processing segments, and 0.0277 pounds VOC per pound methane and 

0.0008 pounds HAP per pound methane in the transmission segment.
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Table 5-5. Alternative Control Options for Pneumatic Devices

Option Description Applicability/Effectiveness Estimated Cost

Range

Install Low 

Bleed Device 

in Place of 

High Bleed 

Device

Low-bleed devices provide the same functional control as a 

high-bleed device, while emitting less continuous bleed 

emissions. 

Applicability may depend on the function of 

instrumentation for an individual device on 

whether the device is a level, pressure, or 

temperature controller.

Low-bleed devices 

are, on average,

comparable in price 

to the high bleed 

version.

Convert to 

Instrument 

Air13

Compressed air may be substituted for natural gas in pneumatic 

systems without altering any of the parts of the pneumatic 

control. In this type of system, atmospheric air is compressed, 

stored in a tank, filtered and then dried for instrument use. For 

utility purposes such as small pneumatic pumps, gas compressor 

motor starters, pneumatic tools and sand blasting, air would not 

need to be dried. Instrument air conversion requires additional 

equipment to properly compress and control the pressured air. 

This equipment includes a compressor, power source, air 

dehydrator and air storage vessel.

Replacing natural gas with instrument air in 

pneumatic controls eliminates VOC emissions 

from bleeding pneumatics. It is most effective 

at facilities where there are a high 

concentration of pneumatic control valves and 

a operator present. Since the system is powered 

by electric compressors, they require a constant 

source of electrical power or a back-up natural 

gas pneumatic device. These systems can 

achieve 100 percent reduction in emissions. 

A complete cost 

analysis is provided 

in Section 5.4.2. 

System costs are

dependent on size of 

compressor, power 

supply needs, labor 

and other equipment. 

Install NonGas Driven 

Control 

Systems in 

place of Bleed 

device14

Mechanical controls operate using a simple design comprised of 

levers, hand wheels, springs and flow channels. The most 

common mechanical control device is the liquid-level float to 

the drain valve position with mechanical linkages. Electricity or 

small electrical motors (including solar powered) have been 

used to operate valves. Solar control systems are driven by a 

solar power cells that actuate mechanical devices using electric 

power. As such, solar cells require some type of back-up power 

or storage to ensure reliability.

Application of mechanical controls is limited 

because the control must be located in close 

proximity to the process measurement. 

Mechanical systems are also incapable of 

handling larger flow fluctuations. Electric 

powered valves are only reliant with a constant 

supply of electricity. Overall, these options are 

applicable in niche areas but can achieve 100 

percent reduction in emissions where 

applicable.

Depending on 

supply of power, 

costs can range from 

below $1,000 to 

$10,000 for entire 

systems.

Enhanced 

Maintenance15

Instrumentation in poor condition typically bleeds 5 to 10 scf 

per hour more than representative conditions due to worn seals, 

gaskets, diaphragms; nozzle corrosion or wear, or loose control 

tube fittings. This may not impact the operations but does 

increase emissions.

Enhanced maintenance to repair and maintain 

pneumatic devices periodically can reduce 

emissions. Proper methods of maintaining a 

device is highly variable and could incur 

significant costs.

Variable based on 

labor, time, and fuel 

required to travel to 

many remote 

locations.
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of the other options identified in Table 5-5 (i.e. mechanical controls and enhanced maintenance), were 

not further conducted for this analysis. 

5.4.1 Low-Bleed Controllers

5.4.1.1 Emission Reduction Potential

As discussed in the above sections, low-bleed devices provide the same functional control as a highbleed device, but have lower continuous bleed emissions. As summarized in Table 5-6, it is estimated on 

average that 6.6 tons of methane and 1.8 tons of VOC will be reduced annually in the production 

segment from installing a low-bleed device in place of a high-bleed device. In the transmission segment, 

the average achievable reductions per device are estimated around 3.7 tons and 0.08 tons for methane 

and VOC, respectively. As noted in section 5.2, a low-bleed controller can emit up to 6 scfh, which is 

higher than the expected emissions from the typical device available on the current market. 

5.4.1.1 Effectiveness

There are certain situations in which replacing and retrofitting are not feasible, such as instances where a 

minimal response time is needed, cases where large valves require a high bleed rate to actuate, or a 

safety isolation valve is involved. Based on criteria provided by the Natural Gas STAR Program, it is 

assumed about 80 percent of high-bleed devices can be replaced with low-bleed devices throughout the 

production and transmission and storage industry segments.

11 This corresponds to 13,632 new highbleed devices in the production segment (out of 17,040) and 67 new high-bleed devices in the 

transmission and storage segment (out of 84) that can be replaced with a new low-bleed alternative. For 

high-bleed devices in natural gas processing, this analysis assumed that the replaceable devices have 

already been replaced with instrument air and the remaining high-bleed devices are safety related for 

about half of the existing processing plants. 

Applicability may depend on the function of instrumentation for an individual device on whether the 

device is a level, pressure, or temperature controller. High-bleed pneumatic devices may not be 

applicable for replacement with low-bleed devices because a process condition may require a fast or 

precise control response so that it does not stray too far from the desired set point. A slower-acting 

controller could potentially result in damage to equipment and/or become a safety issue. An example of 

this is on a compressor where pneumatic devices may monitor the suction and discharge pressure and 

actuate a re-cycle when one or the other is out of the specified target range. Other scenarios for fast 
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Table 5-6. Estimated Annual Bleed Emission Reductions from Replacing a Representative HighBleed Pneumatic Device with a Representative Low-Bleed Pneumatic Device

Segment/Device Type Emissions (tons/year)

Methane VOC HAP

Oil and Natural Gas Production 6.65 1.85 0.07

Natural Gas Transmission and Storage 2.96 0.082 0.002

Minor discrepancies may be due to rounding. 

*Average emission reductions for each industry segment based on the typical emission flow rates from 

high-bleed and low-bleed devices as listed in Table 5-2 by industry segment. 
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and precise control include transient (non-steady) situations where a gas flow rate may fluctuate widely 

or unpredictably. This situation requires a responsive high-bleed device to ensure that the gas flow can 

be controlled in all situations. Temperature and level controllers are typically present in control 

situations that are not prone to fluctuate as widely or where the fluctuation can be readily and safely 

accommodated by the equipment. Therefore, such processes can accommodate control from a low-bleed 

device, which is slower-acting and less precise.

Safety concerns may be a limitation issue, but only in specific situations because emergency valves are 

not bleeding controllers since safety is the pre-eminent consideration. Thus, the connection between the 

bleed rate of a pneumatic device and safety is not a direct one. Pneumatic devices are designed for 

process control during normal operations and to keep the process in a normal operating state. If an 

Emergency Shut Down (ESD) or Pressure Relief Valve (PRV) actuation occurs,

e

the equipment in place 

for such an event is spring loaded, or otherwise not pneumatically powered. During a safety issue or 

emergency, it is possible that the pneumatic gas supply will be lost. For this reason, control valves are 

deliberately selected to either fail open or fail closed, depending on which option is the failsafe.

5.4.1.2 Cost Impacts

As described in Section 5.2.2, costs were based on the vendor research described in Section 5.2 as a 

result of updating and expanding upon the information given in the appendices of the Natural Gas STAR 

Lessons Learned document on pneumatic devices.

11 As Table 5-7 indicates, the average cost for a low

bleed pneumatic is $2,553, while the average cost for a high bleed is $2,338.fThus, the incremental cost 

of installing a low-bleed device instead of a high-bleed device is on the order of $165 per device. In 

order to analyze cost impacts, the incremental cost to install a low-bleed instead of a high-bleed was 

annualized for a 10 year period using a 7 percent interest rate. This equated to an annualized cost of 

around $23 per device for both the production and transmission segments.

Monetary savings associated with additional gas captured to the sales line was estimated based on a 

natural gas value of $4.00 per Mcf.g,16 The representative low-bleed device is estimated to emit 6.65 

tons, or 319 Mcf, (using the conversion factor of 0.0208 tons methane per 1 Mcf) of methane less than 

 

e ESD valves either close or open in an emergency depending on the fail safe configuration. PRVs always open in an 

emergency.

f Costs are estimated in 2008 U.S. Dollars. 

g The average market price for natural gas in 2010 was approximately $4.16 per Mcf. This is much less compared to the 

average price in 2008 of $7.96 per Mcf. Due to the volatility in the price, a conservative savings of $4.00 per Mcf estimate 

was projected for the analysis in order to not overstate savings. 
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Table 5-7. Cost Projections for the Representative Pneumatic Devices

Device Minimum 

cost ($)

Maximum 

cost ($) Average cost ($)

Low-Bleed 

Incremental 

Cost

($)

High-bleed controller 366 7,000 2,388 $165

Low-bleed controller 524 8,852 2,553

*Major pneumatic devices vendors were surveyed for costs, emission rates, and any other pertinent 

information that would give an accurate picture of the present industry.
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the average high-bleed device per year. Assuming production quality gas is 82.9% methane by volume, 

this equals 385.5 Mcf natural gas recovered per year. Therefore, the value of recovered natural gas from 

one pneumatic device in the production segment equates to approximately $1,500. Savings were not 

estimated for the transmission segment because it is assumed the owner of the pneumatic controllers 

generally is not the owner of the natural gas. Table 5-8 provides a summary of low-bleed pneumatic cost 

effectiveness.

5.4.1.3 Secondary Impacts

Low-bleed pneumatic devices are a replacement option for high-bleed devices that simply bleed less 

natural gas that would otherwise be emitted in the actuation of pneumatic valves. No wastes should be 

created, no wastewater generated, and no electricity needed. Therefore, there are no secondary impacts 

expected due to the use of low-bleed pneumatic devices.

5.4.2 Instrument Air Systems

5.4.2.1 Process Description

The major components of an instrument air conversion project include the compressor, power 

source, dehydrator, and volume tank. The following is a description of each component as described in 

the Natural Gas STAR document, Lessons Learned: Convert Gas Pneumatic Controls to Instrument Air:

Compressors used for instrument air delivery are available in various types and sizes, from 

centrifugal (rotary screw) compressors to reciprocating piston (positive displacement) types. 

The size of the compressor depends on the size of the facility, the number of control devices 

operated by the system, and the typical bleed rates of these devices. The compressor is usually 

driven by an electric motor that turns on and off, depending on the pressure in the volume tank. 

For reliability, a full spare compressor is normally installed. Therefore, a minimum amount of 

electrical service is required to power the compressors. 

A critical component of the instrument air control system is the power source required to 

operate the compressor. Since high-pressure natural gas is abundant and readily available, gas 

pneumatic systems can run uninterrupted on a 24-hour, 7-day per week schedule. The 

reliability of an instrument air system, however, depends on the reliability of the compressor 

and electric power supply. Most large natural gas plants have either an existing electric power 
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Table 5-8. Cost-effectiveness for Low-Bleed Pneumatic Devices 

versus High Bleed Pneumatics

Segment

Incremental 

Capital Cost 

Per Unit ($)*

Total Annual Cost 

Per Unit 

($/yr)**

VOC Cost 

Effectiveness 

($/ton)

Methane Cost 

Effectiveness 

($/ton)

without 

savings

with 

savings

without 

savings

with 

savings

without 

savings

with 

savings

Oil and 

Natural Gas 

Production

165 23.50 -1,519 13 net 

savings 4

net 

savings

Natural Gas 

Transmission 

and Storage

165 23.50 23.50 286 -286 8 8

*Incremental cost of a low bleed device versus a high bleed device as summarized in Table 5-7.

 **Annualized cost assumes a 7 percent interest rate over a 10 year equipment lifetime. 
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supply or have their own power generation system. For smaller facilities and in remote 

locations, however, a reliable source of electric power can be difficult to assure. In some

instances, solar-powered battery-operated air compressors can be cost effective for remote 

locations, which reduce both methane emissions and energy consumption. Small natural gas 

powered fuel cells are also being developed.

Dehydrators, or air dryers, are also an integral part of the instrument air compressor system. 

Water vapor present in atmospheric air condenses when the air is pressurized and cooled, and 

can cause a number of problems to these systems, including corrosion of the instrument parts 

and blockage of instrument air piping and controller orifices. 

The volume tank holds enough air to allow the pneumatic control system to have an 

uninterrupted supply of high pressure air without having to run the air compressor 

continuously. The volume tank allows a large withdrawal of compressed air for a short time, 

such as for a motor starter, pneumatic pump, or pneumatic tools, without affecting the process 

control functions.

Compressed air may be substituted for natural gas in pneumatic systems without altering any of the parts 

of the pneumatic control. The use of instrument air eliminates natural gas emissions from natural gas 

powered pneumatic controllers. All other parts of a gas pneumatic system will operate the same way 

with instrument air as they do with natural gas. The conversion of natural gas pneumatic controllers to 

instrument air systems is applicable to all natural gas facilities with electrical service available.13

5.4.2.2 Effectiveness 

The use of instrument air eliminates natural gas emissions from the natural gas driven pneumatic 

devices; however, the system is only applicable in locations with access to a sufficient and consistent 

supply of electrical power. Instrument air systems are also usually installed at facilities where there is a 

high concentration of pneumatic control valves and the presence of a full-time operator that can ensure 

the system is properly functioning.

13

5.4.2.3 Cost Impacts

Instrument air conversion requires additional equipment to properly compress and control the pressured 

air. The size of the compressor will depend on the number of control loops present at a location. A 
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control loop consists of one pneumatic controller and one control valve. The volume of compressor air 

supply for the pneumatic system is equivalent to the volume of gas used to run the existing 

instrumentation – adjusted for air losses during the drying process. The current volume of gas usage can 

be determined by direct metering if a meter is installed. Otherwise, an alternative rule of thumb for 

sizing instrument air systems is one cubic foot per minute (cfm) of instrument air for each control loop.13

As the system is powered by electric compressors, the system requires a constant source of electrical 

power or a back-up pneumatic device. Table 5-9 outlines three different sized instrument air systems 

including the compressor power requirements, the flow rate provided from the compressor, and the 

associated number of control loops.

The primary costs associated with conversion to instrument air systems are the initial capital 

expenditures for installing compressors and related equipment and the operating costs for electrical 

energy to power the compressor motor. This equipment includes a compressor, a power source, a 

dehydrator and a storage vessel. It is assumed that in either an instrument air solution or a natural gas 

pneumatic solution, gas supply piping, control instruments, and valve actuators of the gas pneumatic 

system are required. The total cost, including installation and labor, of three representative sizes of 

compressors were evaluated based on assumptions found in the Natural Gas STAR document, “Lessons 

Learned: Convert Gas Pneumatic Controls to Instrument Air”13 and summarized in Table 5-10.h 

For natural gas processing, the cost-effectiveness of the three representative instrument air system sizes 

was evaluated based on the emissions mitigated from the number of control loops the system can 

provide and not on a per device basis. This approach was chosen because we assume new processing 

plants will need to provide instrumentation of multiple control loops and size the instrument air system 

accordingly. We also assume that existing processing plants have already upgraded to instrument air 

unless the function has a specific need for a bleeding device, which would most likely be safety related.7

Table 5-11 summarizes the cost-effectiveness of the three sizes of representative instrument air systems.

5.4.2.4 Secondary Impacts

The secondary impacts from instrument air systems are indirect, variable and dependent on the electrical 

supply used to power the compressor. No other secondary impacts are expected. 

 

h Costs have been converted to 2008 US dollars using the Chemical Engineering Cost Index. 
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Table 5-9. Compressor Power Requirements and Costs for Various Sized Instrument Air 

Systems*

Compressor Power Requirements** Flow Rate Control Loops

Size of Unit hp kW (cfm) Loops/Compressor

small 10 13.3 30 15

medium 30 40 125 63

large 75 100 350 175

*Based on rules of thumb stated in the Natural Gas STAR document, Lessons Learned: Convert 

Gas Pneumatic Controls to Instrument Air13

**Power is based on the operation of two compressors operating in parallel (each assumed to be 

operating at full capacity 50 percent of the year).
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Table 5-10 Estimated Capital and Annual Costs of Various Sized Representative Instrument Air Systems

Instrument 

Air System 

Size

Compressor Tank Air Dryer Total 

Capital *

Annualized 

Capital**

Labor 

Cost

Total 

Annual 

Costs‡

Annualized Cost 

of Instrument Air 

System

Small $3,772 $754 $2,262 $16,972 $2,416 $1,334 $8,674 $11,090

Medium $18,855 $2,262 $6,787 $73,531 $10,469 $4,333 $26,408 $36,877

Large $33,183 $4,525 $15,083 $135,750 $19,328 $5,999 $61,187 $80,515

*Total Capital includes the cost for two compressors, tank, an air dryer and installation. Installation costs are assumed to be equal to 1.5 times 

the cost of capital. Equipment costs were derived from the Natural Gas Star Lessons Learned document (reference 13) and converted to 2008 

dollars from 2006 dollars using the Chemical Engineering Cost Index. 

**The annualized cost was estimated using a 7 percent interest rate and 10 year equipment life. 

‡Annual Costs include the cost of electrical power as listed in Table 5-9 and labor. 
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Table 5-11 Cost-effectiveness of Representative Instrument Air Systems in the Natural Gas Processing Segment

System 

Size

Number of 

Control 

Loops

Annual Emissions 

Reduction*(tons/year) Value of

Product 

Recovered

($/year)**

Annualized Cost of 

System

VOC Costeffectiveness ($/ton)Methane Costeffectiveness ($/ton)

VOC CH4 HAP without 

savings

with 

savings

without 

savings

with 

savings

without 

savings

with 

savings

Small 15 4.18 15 0.16 3,484 11,090 7,606 2,656 1,822 738 506

Medium 63 17.5 63 0.66 14,632 36,877 22,245 2,103 1,269 585 353

Large 175 48.7 175 1.84 40,644 80,515 39,871 1,653 819 460 228

Minor discrepancies may be due to rounding. 

*Based on the emissions mitigated from the entire system, which includes multiple control loops. 

**Value of recovered product assumes natural gas processing is 82.9 percent methane by volume. A natural gas price of $4 per Mcf was 

assumed. 
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5.5 Regulatory Options

The affected facility definition for pneumatic controllers is defined as a single natural gas pneumatic 

controller. Therefore, pneumatic controllers would be subject to a New Source Performance Standard 

(NSPS) at the time of installation. The following Regulatory alternatives were evaluated:

Regulatory Option 1: Establish an emissions limit equal to 0 scfh.

Regulatory Option 2: Establish an emissions limit equal to 6 scfh.

5.5.1 Evaluation of Regulatory Options

By establishing an emission limit of 0 scfh, facilities would most likely install instrument air systems to 

meet the threshold limit. This option is considered cost effective for natural gas processing plants as 

summarized in Table 5-11. A major assumption of this analysis, however, is that processing plants that 

are constructed at a location with sufficient electrical service to power the instrument air compression 

system. It is assumed that facilities located outside of the processing plant would not have sufficient 

electrical service to install an instrument air system. This would significantly increase the cost of the 

system at these locations, making it not cost effective for these facilities to meet this regulatory option. 

Therefore, Regulatory Option 1 was accepted for natural gas processing plants and rejected for all other 

types of facilities. 

Regulatory Option 2 would establish an emission limit equal to the maximum emissions allowed for a 

low-bleed device in the production and transmissions and storage industry segments. This would most 

likely be met by the use of low-bleed controllers in place of a high-bleed controller, but allows 

flexibility in the chosen method of meeting the requirement. In the key instances related to pressure 

control that would disallow the use of a low-bleed device, specific monitoring and recordkeeping criteria 

would be required to ensure the device function dictates the precision of a high bleed device. Therefore, 

Regulatory Option 2 was accepted for locations outside of natural gas processing plants. 

5.5.3 Nationwide Impacts of Regulatory Options

Table 5-12 summarizes the costs impacts of the selected regulatory options by industry segment.

Regulatory Option 1 for the natural gas processing segment is estimated to affect 15 new processing 

plants with nationwide annual costs discounting savings of $166,000. When savings are realized the net 
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Table 5-12 Nationwide Cost and Emission Reduction Impacts for Selected Regulatory Options by Industry Segment

Industry 

Segment

Number 

of 

Sources 

subject to 

NSPS*

Capital Cost 

Per 

Device/IAS 

($)**

Annual Costs 

($/year)

Nationwide Emission 

Reductions (tpy)†

VOC Cost 

Effectiveness 

($/ton)

Methane Cost 

Effectiveness 

($/ton)

Total Nationwide Costs

($/year)

without 

savings

with 

savings VOC Methane HAP without savings

with 

savings

without 

savings

with 

savings

Capital 

Cost

Annual 

without 

savings

Annual with 

savings

Regulatory Option 1 (emission threshold equal to 0 scfh)

Natural Gas 

Processing 15 16,972 11,090 7,606 63 225 2 2,656 1,822 738 506 254,576 166,351 114,094

Regulatory Option 2 (emission threshold equal to 6 scfh)

Oil and 

Natural Gas 

Production

13,632 165 23 (1,519) 25,210 90,685 952 13 net 

savings 4 -228 2,249,221 320,071 (20,699,918)

Natural Gas 

Transmission 

and Storage

67 165 23 23 6 212 0.2 262 262 7 7 11,039 1,539 1,539

Minor discrepancies may be due to rounding. 

* The number of sources subject to NSPS for the natural gas processing and the natural gas transmission and storage segments represent the 

number of new devices expected per year reduced by 20 percent. This is consistent with the assumption that 80 percent of high bleed devices 

can be replaced with a low bleed device. It is assumed all new sources would be installed as a high bleed for these segments. For the natural 

gas processing segment the number of new sources represents the number of Instrument Air Systems (IAS) that is expected to be installed, 

with each IAS expected to power 15 control loops (or replace 15 pneumatic devices). 

** The capital cost for regulatory option 2 is equal to the incremental cost of a low bleed device versus a new high bleed device. The capital 

cost of the IAS is based on the small IAS as summarized in Table 5-10. 

‡ Nationwide emission reductions vary based on average expected emission rates of bleed devices typically used in each segment industry 

segment as summarized in Tables 5-2. 
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annual cost is reduced to around $114,000. Regulatory Option 2 has nationwide annual costs of 

$320,000 for the production segment and around $1,500 in the natural gas transmission and storage 

segment. When annual savings are realized in the production segment there is a net savings of $20.7 

million in nationwide annual costs. 
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5.6 References

 

1 U.S. Environmental Protection Agency. Greenhouse Gas Emissions Reporting From the 

Petroleum and Natural Gas Industry: Background Technical Support Document. Climate Change 

Division. Washington, DC. November 2010.

2 U.S Environmental Protection Agency. Methodology for Estimating CH4 and CO2 Emissions 

from Natural Gas Systems. Greenhouse Gas Inventory: Emission and Sinks 1990-2008. 

Washington, DC.

3 U.S Environmental Protection Agency. Methodology for Estimating CH4 and CO2 Emissions 

from Petroleum Systems. Greenhouse Gas Inventory: Emission and Sinks 1990-2008. 

Washington, DC.

4 Radian International LLC. Methane Emissions from the Natural Gas Industry, Vol. 2: Technical 

Report. Prepared for the Gas Research Institute and Environmental Protection Agency. EPA600/R-96-080b. June 1996.

5 Radian International LLC. Methane Emissions from the Natural Gas Industry, Vol. 3: General 

Methodology. Prepared for the Gas Research Institute and Environmental Protection Agency. 

EPA-600/R-96-080c. June 1996.

6 Radian International LLC. Methane Emissions from the Natural Gas Industry, Vol. 5: Activity 

Factors. Prepared for the Gas Research Institute and Environmental Protection Agency. EPA600/R-96-080e. June 1996.

7 Radian International LLC. Methane Emissions from the Natural Gas Industry, Vol. 12: 

Pneumatic Devices. Prepared for the Gas Research Institute and Environmental Protection 

Agency. EPA-600/R-96-080k. June 1996.

8 Radian International LLC, Methane Emissions from the U.S. Petroleum Industry, draft report for 

the U.S. Environmental Protection Agency, June 14, 1996.

9 ICF Consulting. Estimates of Methane Emissions from the U.S. Oil Industry. Prepared for the 

U.S. Environmental Protection Agency. 1999.

10 ENVIRON International Corporation. Oil and Gas Emission Inventories for the Western States. 

Prepared for Western Governors‟ Association. December 27, 2005. 

11 U.S. Environmental Protection Agency. Lessons Learned: Options for Reducing Methane 

Emissions From Pneumatic Devices in the Natural Gas Industry. Office of Air and Radiation: 

Natural Gas Star. Washington, DC. February 2004

12 Memorandum to Bruce Moore from Heather Brown. Gas Composition Methodology. July 2011

13 U.S. Environmental Protection Agency. Lessons Learned: Convert Gas Pneumatic Controls to 

Instrument Air. Office of Air and Radiation: Natural Gas Star. Washington, DC. February 2004
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5-27

 

14 U.S. Environmental Protection Agency. Pro Fact Sheet No. 301. Convert Pneumatics to 

Mechanical Controls. Office of Air and Radiation: Natural Gas Star. Washington, DC. 

September 2004.

15 CETAC WEST. Fuel Gas Best Management Practices: Efficient Use of Fuel Gas in Pneumatic 

Instruments. Prepared for the Canadian Association of Petroleum Producers. May 2008. 

16 U.S. Energy Information Administration. Annual U.S. Natural Gas Wellhead Price. Energy 

Information Administration. Natural Gas Navigator. Retrieved online on 12 Dec 2010 at 

<http://www.eia.doe.gov/dnav/ng/hist/n9190us3a.htm>