ISSUE DATE: 06/22/2011

PROGRAM INFORMATION BULLETIN NO. P11-47

FROM : LINDA F. ZEILER

Acting Director of Technical Support

NEAL H. MERRIFIELD

Administrator for

Metal and Non-Metal Mine Safety and Health

SUBJECT: Compressed Gas System Leakage 

Who needs this information?

This Program Information Bulletin applies to Mine Safety and Health Administration 

(MSHA) personnel, metal and nonmetal mine operators, miners’ representatives, 

manufacturers of mine equipment and mining products, and repair shop facilities should 

have this information.

Why is MSHA issuing this Program Information Bulletin?

This Program Information Bulletin (PIB) is issued to inform mine operators and users of 

compressed gas systems of the potential for excessive leakage from compressed gas 

systems. The entire metal/nonmetal mining industry is being alerted because 

compressed gas systems are used in a wide variety of applications. 

Background

Excessive compressed gas system leakage can be caused by component 

manufacturing defects, improper assembly (such as incorrect thread preparation), 

damage from transportation, use of incompatible leak testing fluids, and improper 

cleaning of system components during assembly. This PIB addresses a refuge 

alternative manufacturer's experience with excessive leakage on its 6000 psi breathable 

air cylinders. That particular situation has been resolved, and all of the leaking cylinders 

have been removed from service. MSHA’s investigation into the excessive leakage 

condition was unable to determine whether the leakage was associated with

manufacturing, installation, or transportation of the cylinder and valve assemblies. 
However, this experience highlights the importance of taking steps to ensure that there 

is not excessive leakage from gas systems.

Information

Which compressed gas systems does this PIB address?

All compressed gas systems are addressed with this bulletin. Compressed gas 

systems are used for providing compressed air, oxygen, and gases used in welding or 

other processes and systems used in mining. 

What is excessive leakage?

A minimal amount of leakage is inherent in all compressed gas systems. This PIB is 

intended to address systems that leak at a rate that would ultimately prevent a system 

from performing its intended function or that would dangerously enrich gas 

concentrations around the leaking system. Excessive leakage may be detected during 

manufacturing, shipment, or on-shift examinations.

Leakage can be detected using specially formulated leak detection fluid. If any bubbles 

are identified in the fluid during testing, the system being checked would be considered 

to be leaking excessively.

Other methods for detecting leakage are commercially available to manufacturers and 

mining operations. Any leakage that is identified at a rate that would ultimately prevent 

a system from performing its function before normally scheduled maintenance or 

replacement or that would create a hazard is considered excessive.

Pressure gauges are graduated such that small pressure changes between inspections 

may not be visibly noticeable. Therefore, any visible drop in pressure shown on the 

gauges normally would be indicative of excessive leakage. 

What are the potential safety concerns with compressed gas system leakage?

Excessive leakage from a compressed gas system can cause the gas to leak to a point 

where there is not enough compressed gas to perform its intended function in 

accordance with that system’s requirements.

If compressed oxygen or air is used in breathing systems, leakage of these systems 

would diminish the amount of oxygen or breathable air available to provide protection. 

Compressed gas leakage could also result in enrichment of the area in which the 

system is housed. These areas should be ventilated to avoid enriching that space and 

increasing the risk of adverse health effects and/or fire or explosion. The oxygen safety 

hazard alert on the MSHA website contains more information concerning good practices 

for all compressed gas systems:

http://www.msha.gov/Alerts/OxygenSafety11202009.pdf
What action should be taken by compressed gas system suppliers?1

1. Perform inspection of vendor-provided system components to assure compliance 

with specifications. 

2. Consider the Compressed Gas Association (CGA) acceptable maximum leakage 

rates when determining the necessary number of cylinders to perform the 

intended system function, so that gas quantities are not materially diminished 

before scheduled, routine preventive maintenance activities, such as refill 

schedules and DOT inspections. 

3. Follow the proper torque specifications when assembling the system’s 

components.

4. Use the appropriate pipe thread preparation materials (e.g., pipe dope, Teflon®, 

etc.) for the compressed gas system being assembled. 

5. Conduct leak inspections after the compressed gas system is assembled to 

assure that leakage does not exceed the CGA acceptable maximum rates before 

shipment to customers. 

6. Leak inspections should be performed by using leak detection fluids or other 

means that are not potentially corrosive or otherwise damaging to the 

compressed gas system components. Use certified ammonia-free leak 

inspection fluids.

What action should be taken by mine operators?

Mine operators should have spare compressed gas systems or components on-site in 

the event leaking compressed gas systems are identified and removed from service. 

The spare compressed gas systems or components will enable the mine operator to 

continue to provide protection in the event of a leak while maintaining mining 

operations. Maintenance should not be performed on pressurized systems located 

underground. This includes filling and changing of cylinders.

Mine operators should examine their compressed gas systems upon receipt and

immediately after any transportation, and they must examine compressed gas systems 

under 30 C.F.R. § 56/57.18002(a) during on-shift examinations, to determine if the 

systems have any signs of damage or excessive leakage (see supplier action item nos. 

5 and 6 above) that could adversely affect the safety or health of miners. In addition, 

under 30 C.F.R. § 56/57.13015, compressed gas systems must be inspected in 

accordance with the National Board Inspection Code. If mine operators identify an 

excessively leaking or damaged compressed gas system, they should contact the 

supplier to have the system re-examined for leaks and for sufficient quantities of 

compressed gas. If an examination reveals damage or excessive leakage that could 

affect the health or safety of miners, the system must be timely repaired or removed 

from service pursuant to 30 C.F.R. §§ 56/57.14100(b) and 56/57.18002(a). 

What must be done before a compressed gas system is returned to service?

 1 Mine operators who purchase systems directly from manufacturers also should perform these actions.
Under 30 C.F.R. §§ 56/57.14100(b) and 56/57.18002(a), compressed gas systems or 

components removed from service must be replaced or repaired for return to service so 

as to prevent excessive leakage and provide sufficient quantities of compressed gas. 

At the completion of each repair, the person conducting the maintenance or repair 

should make a record of all corrective actions taken. 

What is MSHA's authority for this PIB?

The Federal Mine Safety and Health Act of 1977, as amended, at § 110(h) (30 U.S.C. 

§§ 820(h)); 30 C.F.R. §§ 56/57.13001, 56/57.13015, 56/57.13019, 56/57.14100, and 

56/57.18002. 

Internet Availability

This information bulletin may be viewed on the Internet by accessing MSHA's home 

page at http://www.MSHA.gov and then choosing "Compliance Info," and "Program 

Information Bulletins."

Who are the MSHA contact persons for this PIB?

Metal/Non-Metal Mine Safety and Health

Marvin Lichtenfels, CSP, ARM

(202) 693-9606

E-mail: lichtenfels.marvin@dol.gov

Technical Support, Approval and Certification Center

Rob Parry, (304) 547-2046

E-mail: parry.robert@dol.gov

Who will receive this PIB?

MSHA Program Policy Manual Holders 

Miners' Representatives

Metal/Nonmetal Mine Operators 

Manufacturers of Mine Equipment and Mining Products 

Mine Equipment Repair Shop Facilities 

Special Interest Groups