ISSUE DATE: 07/31/09 

PROGRAM INFORMATION BULLETIN NO. P09-20 

FROM: KEVIN G. STRICKLIN Charles Thomas for

 Administrator for 

 Coal Mine Safety and Health 

 LINDA F. ZEILER

 Acting Director of Technical Support 

SUBJECT: Re-Issue P97-24 - Portable Methane Detectors Magnetically 

 Attached to Mining Machinery (The “Gizmo”) 

Scope

This Program Information Bulletin (PIB) applies to Mine Safety and Health 

Administration (MSHA) Coal Mine Safety and Health (CMS&H) enforcement 

personnel, equipment manufacturers, and underground coal mine operators. 

Purpose

This bulletin informs MSHA enforcement personnel, equipment manufacturers, and 

mine operators of the results of testing of portable methane detectors attached to 

mining machinery via brackets and magnets (in a configuration commonly called the 

“gizmo”) to check for methane at the face in accordance with Title 30, Code of Federal 

Regulations (30 C.F.R.) § 75.362(d)(2). The purpose of the testing was to determine if 

the performance of the handheld methane detectors is affected by the magnet. 

Information

MSHA has conducted accuracy tests on several methane detectors placed in a bracket 

attached to various magnets. MSHA used the accuracy requirements specified in 

30 C.F.R. § 22.7(d)(2) as the basis for testing and for determination of acceptability. The 

performance of the following detectors was not affected by the presence of the magnet: 

 CSE Models 102 and 102-LD 

 Industrial Scientific Model CD210 

 MSA “Spotter” P/N 474115 
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A survey conducted by CMS&H showed that three types of detectors comprised 89 

percent of the units used with magnets: the CSE Models 102 and 102-LD, and the 

Industrial Scientific Model CD210. 

Also being used are the Industrial Scientific Models MX250 and CMX270. Samples of 

these were not available for testing from the manufacturer because they are no longer 

produced. Likewise, samples could not be readily supplied by the districts. The survey 

shows that only 4 percent of the mines are using either of these types of detectors. 

Because of their similarity to detectors that were tested, the Industrial Scientific Models 

MX250 and CMX270 should not be affected by magnets. MSHA has made no 

determination as to other detectors in use. Their performance may or may not be 

affected by the presence of the magnets. 

Background

Various mine operators have developed a method of sampling the atmosphere at the 

face of extended-cut mining sections that allows measurement of the methane 

concentration at this location without exposing personnel to unsupported roof. 

The method uses either a commercial or a custom detector bracket mounted to a magnet 

either directly or by means of a post. The post is made of steel or flexible conduit and 

varies in length from 2 to 36 inches. The “pull” rating of the magnets ranges from 90 to 

250 pounds. 

Each MSHA District Office investigated the equipment comprising each “gizmo” used 

underground and provided the information to the Approval and Certification Center 

(A&CC). The A&CC then obtained representative samples of the magnets, brackets, 

and detectors. 

The magnets obtained and tested did not include every magnet type reported to be in 

use. Rather, the magnet/bracket/detector configurations that presented the greatest 

likelihood of magnetic interference were determined and tested, without testing every 

configuration. 

For initial testing, MSHA mixed test gas per 30 C.F.R. § 22.7(d); monitored the 

concentration of the test gas; introduced the test gas to the detector via the appropriate 

calibration adapter; and monitored the reading on the methane detector while it was 

mounted in the “gizmo” which was placed on a laboratory bench. 

A magnet's greatest effect on a methane detector would most likely occur with an 

alternating magnetic field, which would require the magnet to rotate in relation to the 

detector. The magnet used with the “gizmo” in the field will remain substantially 

stationary in relation to the detector. To simulate the magnetic field moving in relation 

to the detector, vibration tests were performed. The “gizmo” was magnetically attached 
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to a vibration table that was operated per 30 C.F.R. § 27.39(a). The accuracy of the 

detectors was then tested in the same manner as before. A complete report of testing is 

available from the A&CC, Division of Electrical Safety. 

Authority

30 C.F.R. § 22.7; 30 C.F.R. § 75.320(a); and 30 C.F.R. § 75.362(d)(2). 

Issuing Office and Contact Person

Technical Support, Approval and Certification Center 

David C. Chirdon, (304) 547-2026 

E-mail: chirdon.david@dol.gov

Coal Mine Safety and Health, Safety Division 

Michael G. Kalich, (202) 693-9714 

E-mail: kalich.michael@dol.gov

Distribution

MSHA Coal and All-Volume Program Policy Manual Holders 

Underground Coal Mine Operators 

Manufacturers of Electric Equipment