After 12 years of delays, the coal industry has been ordered by the Labor Department to supply miners with emergency breathing devices or face fines and possible mine shutdowns.

Joseph A. Lamonica, head of coal mine safety for the Mine Safety and Health Administration, said all but about 620 of the nation's 2,500 underground coal mines have the devices, called self-contained self-rescuers, which are designed to provide oxygen to miners for at least one hour during emergencies. About one-fifth of all underground mining fatalities are a result of asphyxiation.

Congress first required the devices in 1970, but legal challenges by the coal industry delayed the regulation until June. When the rule took effect, MSHA said it would not penalize mine owners who didn't have the devices, because manufacturers had delayed making them in fear the regulation would be revoked. MSHA extended the deadline to Oct. 1.

MSHA then discovered that coal operators had refused shipments of the devices, which cost about $500 each, and had caused further delays by ordering nearly 80 percent of them from a single manufacturer, though five small companies make them.

More recently, coal operators claimed that the self-rescuers, some of which contain bottled oxygen, were unsafe. MSHA said that tests show the controversial devices "do not possess any inherent hazards" but warned that they are "not toys" and could cause fires or explosions in mines if handled carelessly.

MSHA inspectors began issuing citations Friday to operators without the rescuers. Fines range from $20 to $10,000. If mine operators refuse to provide the rescuers after a period of three weeks, MSHA could order miners out of the mine or shut down the operation. The agency said it decided to enforce Friday's deadline in part because October marks the beginning of what has historically been the most dangerous six-month period in the mines.