EFFECTIVE DATE: 04/30/2012 EXPIRATION DATE: 03/31/2014

(Reissue of I10-V-12)

PROCEDURE INSTRUCTION LETTER NO. I12-V-12

FROM: KEVIN G. STRICKLIN

Administrator for

Coal Mine Safety and Health

SUBJECT: Reissue of I10-V-12 - Maintaining Methane Monitors in Proper 

Operating Condition for Mining Equipment

Scope

This Procedure Instruction Letter (PIL) applies to Coal Mine Safety and Health 

(CMS&H) District Managers, Supervisors, Specialists, and Inspectors.

Purpose

The purpose of this PIL is to provide instruction for district personnel regarding the 

inspection of methane monitors to ensure the monitors are permissible and that they are 

properly operating.

Procedure Instructions

Under 30 C.F.R. § 75.342, methane monitors on mining equipment must be maintained 

in permissible and proper operating condition. To eliminate potential hazards 

associated with methane liberation in the working places, it is imperative that 

equipment with methane monitors be operated only when the methane monitor is 

functioning properly.

When inspectors encounter mining equipment that is equipped with methane monitors,

they should conduct a visual examination and functional test to ensure that the 

monitors are operating properly, not “bridged out,” and do not have material covering 

the sensor head. The functional test may consist of activating a test circuit on the 

monitor or application of calibration gas. Inspectors should test methane monitors with 

a known methane air test mixture when it is suspected that the monitor is defective or 

improperly calibrated. Inspectors should also check the examination records to ensure 

the required calibration tests are being performed at least once every 31 days.
2

Background

Methane monitors ensure that miners are provided with the earliest possible warning 

when excessive quantities of methane accumulate in the working places. Some mine 

operators are defeating the purpose of a methane monitor either by placing material 

over the sensor head of the monitor or “bridging out” the electrical safety components 

of the monitors. Placing material over the sensor head will prevent the monitor from 

detecting excessive and dangerous concentrations of methane in the mine. Similarly, 

“bridging out” the electrical components of the monitors will prevent the mining 

equipment from shutting down when methane reaches the two percent cut-off level. 

Methane ignitions and potential explosions could occur if these practices continue.

Methane monitors are critical safety devices designed to protect miners from methane 

explosions. These monitors provide the first warning of elevated levels of methane by 

giving a warning signal at one percent and automatically shutting down mining 

equipment when methane concentrations reach two percent. Mining equipment that 

continues to operate under such conditions could result in a face ignition or violent 

explosion.

Authority

The Federal Mine Safety and Health Act of 1977, as amended, 30 U.S.C. § 801 et seq.;

30 C.F.R. §§ 75.342 (a)(4) and 75.503.

Internet Availability

This PIL may be viewed on the Internet by accessing MSHA's home page at 

(www.msha.gov), choosing "Compliance Info" and "Procedure Instruction Letters."

Filing Instructions

This instruction letter should be filed behind the tab marked "Procedure Instruction 

Letters" in the binder for Program Policy Handbooks and Procedure Instruction Letters.

Issuing Office and Contact Person

Coal Mine Safety and Health, Safety Division

Michael G. Kalich, (202) 693-9714

E-mail: kalich.michael@dol.gov

Distribution

MSHA Program Policy Manual Holders