The Mine Safety and Health Administration has decided to crack down on coal mine owners who have been avoiding a 10-month-old regulation requiring them to provide underground miners with a new type of emergency breathing device.

Congress first required the devices 12 years ago, but legal challenges by the coal industry delayed the regulation until last June. When the new rule took effect, MSHA said it would not penalize mine owners who didn't have the new devices, as long as they could prove that they had ordered them. MSHA justified its liberal enforcement policy by saying that manufacturers needed more time to produce enough of the $350-plus units for the nation's 2,100 underground mines. Manufacturers had delayed making the units because they were afraid the regulation would not be approved.

Now, MSHA has decided to toughen its stance, because only 7,807 of the devices are being used in an industry that employs 116,000 underground miners. Mine operators have been refusing delivery of the units, MSHA said, and they now must "show evidence" of a delivery schedule or face penalties. Manufacturers should finish producing enough of the devices by Oct. 1, MSHA said.

The devices, which provide a one-hour supply of oxygen, are intended to increase a miner's chances of surviving after an explosion or fire; about one-fifth of all underground mining fatalities are caused by asphyxiation. The units are supposed to replace a breathing device that filters out carbon monoxide but does not supply oxygen. The old units, which still exist in most mines, often heated up in use, burning the miner's mouth.