MSHA Fire Suppression and Fire Protection Advisor

Glossary for Electrical Equipment

Multipurpose dry chemical with a 2A:10B:C rating, listed or approved by a nationally recognized independent testing laboratory.

"Attended" for Electrical Equipment has the following meanings:

In a Primary Escapeway (Attended) means:

• The equipment operator will be on the mobile equipment or immediately adjacent to the equipment and be capable of activating the fire suppression system in the event of a fire.

When 75.344 applies to electric-operated compressors (75.344(a)(1)) (Attended) means:

• Continuously attended by a person designated by the operator who can see the compressor at all times during its operation. Any designated person attending the compressor must be capable of activating the fire suppression system and deenergizing or shutting off the compressor in the event of a fire.

When 75.1107 applies (75.1107-1(c)) (Attended) means:

1. Any machine or device regularly operated by a miner assigned to operate such machine or device.
2. Any machine or device in the direct line of sight and located within 500 feet of a jobsite regularly occupied by a miner assigned to perform job duties at the jobsite during each production shift.

Machines and devices described above must be inspected for fire and the input powerline deenergized when workmen leave the area for more than 30 minutes.

Program Policy states that to be considered as attended, the equipment be in line of sight of a miner at least once during a 30-minute period.

A structure/area that provides protection against flame spread for at least 1 hour when subjected to a fire test incorporating an ASTM E119-88 time/temperature heat input or equivalent. The following types of installations are considered to be noncombustible structures as required by 75.340.

1. Installations that are manufactured as packaged units fully enclosed in a metal housing --

• Power centers;
• Rectifiers and transformer stations that use dry-type transformers; or
• Transformers filled with nonflammable fluid or inert gas.

2. Underground battery charging stations --

• that are enclosed in substantial metal housings;
• that are used to charge batteries that are also enclosed in substantial metal housings; and
• where batteries remain on the machine during charging.

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