CLEARING THE AIR: Managing Director of Competition Gary Nelson said NASCAR is making steady progress on dealing with carbon monoxide. The deadly gas, which is colorless, odorless and found in exhaust fumes, has left many drivers who have been exposed feeling nauseous. NASCAR ratcheted up its approach to the problem when Lexington, Va., native Rick Mast was forced to retire after being diagnosed with chronic carbon monoxide poisoning.

Random testing of volunteer drivers to measure pre- and postrace levels of carbon monoxide has yielded nothing alarming throughout the year's first four races, Nelson said. NASCAR crews and inspectors have been trained to be more vigilant in examining their cars for small cracks or improper seals that might allow carbon monoxide to seep into the cockpit.

"We think we made the most progress talking to the crews and crew chiefs and training inspectors on what to look for," Nelson said. "If they notice anything, they bring it to the crews' attention. . . . We've made tremendous gains."

Engineers at NASCAR's Research and Development Center in Concord, N.C., also are working on a catalyst system to filter air inside the car.

"The efficiency of the catalyst is dependent on the speed that the air flows through it," Nelson said. "If you have contaminated air and you run it through this catalyst too fast, the catalyst doesn't do the job. You run it through too slow, it doesn't do the job. We're trying to optimize that, and we're very encouraged that we're seeing results."

MOTOR MALADIES: Kurt Busch's engine woes continued during the first Winston Cup practice session yesterday. The motor in Busch's Ford expired during his warmup laps. Busch turned the 18th-fastest lap in the final practice with a fresh supply of horsepower.

Roush Racing engines have failed six times in the past three race weekends.

IN THE WALL: Michael Waltrip's Chevrolet was the lone casualty in practice for today's Carolina Dodge Dealers 400. Waltrip banged the right side of his car against the Turn 2 wall just minutes before the end of the final practice and will need a backup car today.

Points leader Matt Kenseth led the final practice with a 167.385-mph lap, followed by Hendrick Motorsports teammates Jimmie Johnson (166.141) and Jeff Gordon (166.062).

BUSCH POSTPONED: Rain began falling on the pace laps of the DarlingtonRaceway.com 200 and didn't let up the rest of the afternoon, postponing the Busch Series event to 11 a.m. tomorrow. The race will be televised by FX.

Weather has disrupted the schedule in all five of NASCAR's race weekends so far in 2003.

BATTING .062: Dale Jarrett's 31 Winston Cup victories rank him 19th all time, but he kidded that the triumphs don't seem as impressive with his 500th start looming today.

"Wow, my winning percentage isn't very good when you look at it that way," said Jarrett, who made his first start for Richmond's Emanuel Zervakis in 1984 at Martinsville. "It's hard to believe it's been 500 races. There are a lot of them I can remember, and a lot of them I can forget, too."

STERLING'S SUGGESTIONS: With NASCAR considering a realignment of its schedule for 2004, Sterling Marlin would like to eliminate trips to Sonoma, Calif., and Watkins Glen, N.Y., where left- and right-hand turns are required.

"I think they should look at adding some Saturday night races and dropping the road courses," Marlin said. "It would save money for the teams. I ain't got nothing against going out to California, but I think if we had a good track like Richmond where we could put on a good show, it would be OK." -Nate Ryan