The PIB is meant to let mines know the specific boundaries for 30 CFR, 19.1(b), the electric cap lamp regulation, on compliant units and associated electronic circuitry, and that it will bear resemblance to another well-known section of federal law.

“MSHA intends to evaluate cap lamps for compliance using MSHA's Criteria for the Evaluation and Test of Intrinsically Safe Apparatus and Associated Apparatus [http://www.msha.gov/techsupp/acc/application/acri2001.pdf], where applicable, in addition to the existing 30 CFR, 19.1(b) requirements,” MSHA said.

“[The] regulation was originally promulgated in 1939 and has not been substantially updated since," it said of Part 19.

“At the time … authors did not address more recent developments in the design of electric cap lamps."

The area of concern for the units is protection against explosion hazard, which is encompassed in 30 CFR, 19.7 with the following preface:

“Unless properly designed, electric cap lamps may present two sources of probable explosion hazards: ignition of an explosive atmosphere by the heated filament of the bulb in case the bulb glass is accidentally broken, and ignition by sparks or flashes from the battery…."

The agency said that while several safety requirements were outlined at the time, they included only the technology in use then. It was also commonplace for many years that the only design submitted to MSHA for approval had batteries of acid or lead connected directly to an electric headpiece filament.

“Recent electric cap lamp designs include newer battery chemistries such as nickel metal hydride and lithium ion [and] these new battery assemblies typically include electronic control circuitry," it said in the PIB.

“Additionally, electric cap lamps are now routinely designed to deliver power to accessories such as radio frequency identification (RFID) tags, and personal messaging devices or an accessory receptacle (power take-off or PTO) to power remote control transmitters."

MSHA added that by nature of design the accessories introduce additional electronic circuitry that must be reviewed.

Alternate technologies are also beginning to take centre stage, such as a trend in applications submitted for units that incorporate fluorescent lamps or light emitting diodes (LEDs).

“Section 19.7(e) requires cap lamp battery current to be restricted to a value that will not produce sparks that could ignite an explosive mixture of methane and air," MSHA noted.

“In order to ensure that an adequate degree of safety is provided on new cap lamp designs, the A&CC [MSHA Approval and Certification Center] is applying the Criteria for the Evaluation and Test of Intrinsically Safe Apparatus and Associated Apparatus to the evaluation of MSHA approval requests for electric cap lamps."

The agency is encouraging mine personnel, equipment producers and other interested parties to pass on the information to others; the full document is available for viewing at its website.