Senate lawmakers reached a bipartisan deal Tuesday aimed at improving safety at the nation's coal mines, including increasing oxygen supplies for miners.

Sens. Mike Enzi, R-Wyo., and Edward Kennedy, D-Mass., the top lawmakers on the committee that oversees workplace safety issues, plan to hold a hearing, known as a markup session, on their legislation Wednesday.

Both lawmakers had promised families of the miners killed in the January accident at the Sago mine in West Virginia that they would take legislative action to improve safety conditions at coal mines. One man was killed in the blast and 11 others died from carbon monoxide poisoning.

The Senate bill would require each miner to have at least two hours of oxygen available to them instead of the one-hour rule that has been the policy. It also would require mine operators to store extra oxygen packs every 30 minutes along escape routes for miners trying to evacuate.

The measure would require that any emergency air supplies stashed in the mines be monitored for reliability. The sole survivor of the Sago accident, Randal McCloy Jr., has said that at least four of the miners' air packs did not work, forcing the men to share their oxygen.

Family members of some victims were expected to appear at a rally on Capitol Hill later to press for new safety laws.

House Democrats on the committee that oversees mine safety have also drafted a mine safety bill.

Under the Senate bill, seals for abandoned sections of mines would have to be made stronger. The cause of the blast at the Sago mine about 100 miles north of Charleston has not been determined but is believed to have occurred in an abandoned section of the mine that had been sealed off.

The bill also would require rescue teams to be more familiar with the mines they cover, be located closer, and have better training.