BROOKLYN, Mich. -- Several Sprint Cup cars are being monitored this weekend for possibly dangerous carbon monoxide levels at Michigan International Speedway.

The decision to test several cars, including the No. 11 Toyota of driver Denny Hamlin, comes in the wake of complaints by some drivers that the new car being run full-time for the first time this season is often unbearably hot inside the cockpit.

Although Carl Edwards has not been one of the drivers complaining about the heat inside the car -- in fact, he said he welcomes it -- he did applaud NASCAR for taking steps to ensure the safety of the drivers with the carbon monoxide testing.

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I've felt so terrible in a car before that I literally thought it was permanent [physical] damage. I think that comes from the carbon monoxide, and that's not safe for anyone.

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CARL EDWARDS

"I think we'll learn more with this [testing], the carbon monoxide measure," Edwards said. "I've felt so terrible in a car before that I literally thought it was permanent [physical] damage. I think that comes from the carbon monoxide, and that's not safe for anyone. So I have a feeling that we're probably going to find out it's not the heat as much as it is that."

John Darby, Sprint Cup Series director, said NASCAR has been paying close attention to complaints about heat inside the car. But he insisted that the problem can be addressed easily, if only teams are willing to explore all options within the car that already are available to them.

Darby said he has been surprised to investigate some cars where heat has been an issue, only to find that many such options are being ignored.

"You see no fresh-air vents, no active air conditioning, you see no attempt at all to work within what they have to work with," Darby said. "So you have to go back and re-educate them. The sad part is that some of the simplest things that can circulate air -- it's like you rolling down your window when you're going down the highway -- somebody has convinced them they shouldn't use it because it's a performance loss.

"All I'm saying is there is a full menu of ways that drivers can deal with heat in their cars. And if you're only using one, then you try using two, and maybe next you use three, and so on. I just talked to Carl Edwards, and he told me he didn't even break a sweat [last week at Pocono, where others complained] -- and he drives the same kind of cars everybody else does."

Edwards said he has never had a problem with the heat generated inside the cockpit of the Cup cars he has driven, old or new.

"I haven't run an air-conditioning unit in my car for two years; we just blow whatever the outside ambient air temperature is on my head, and I think it's fine," Edwards said. "I don't have any issue with it. I hope they don't implement some sort of rules or change something or whatever. I think we've got enough creature comforts as it is."

Of course, Edwards is 28 years old and prides himself on keeping physically fit. He is dedicated to one of the most rigorous workout regimens of any driver.

But Hamlin, also 28, also is one of the more physically fit drivers on the circuit. And he complained perhaps the loudest and the longest about the heat inside the new car after Pocono.

Not that it took him long to recover. Asked how long it took on Friday, Hamlin replied: "Actually, I was fine by the next day. I went on a bike ride for 15 miles, ran for about three [miles] and played basketball for about three hours. So I was definitely good on Monday. But the heat was definitely an issue after the race."

He said that his team is more than willing to work with NASCAR to address what he sees as a serious issue.

"I think it's an issue that NASCAR is going to address and they've already started doing it here, testing six or seven of us on our [carbon monoxide] levels before and after practice," Hamlin said. "They're going to do it after final practice and then again after the race to see what's going on with it. They've already taken steps in the right direction. Then for us as a race team, we've got to get better with our ventilation as well."

Darby added that some changes were made to the new car after complaints and problems surfaced last year when it was used part-time. He said that more changes might be made following this season, but urged competitors to first make certain they are doing all they can to keep cool with how it currently is set up.

"The exhaust actually ran through the frame rail [last year]. A frame rail can be a big heat conductor," Darby said. "So the exhaust pipes have been lowered below the frame rail to create fresh-air movement above and below the pipes.

"We do know that unleaded fuel produces a little more heat than what leaded fuel did. But I'm talkin' like 10, 20 degrees. It's not a hundred degrees or something like that. So there's one thing you could look at that could potentially increase the heat in that car. But a lot of it still surrounds the fact that there is so much available to be used to cool the car that is not being used; we gotta get that bridge crossed first."