When a maintenance man was called yesterday to fix an air shaft screen in the roof above the business office of a Centreville 7-Eleven Store, he found something unusual.

"Hey, there are a pair of sneakers in here," he yelled down to 7-Eleven employe Pam Blakeman. When told to pull them out, the maintenance man replied, "I can't. Somebody's still inside them."

Three hours earlier, Blakeman had locked the doors of the convenience store when a group of teen-agers began harassing and flirting with her and asking for free beer. When the youths got tired and left, she looked outside the store and noticed a hole in the air shaft screen.

One youth, according to Centreville Rescue Squad Capt. Leon Buckley, had climed down the air shaft after cutting the screen with a pocket knife and apparently planned to enter the store.

"Not only did he get stuck upside down about eight feet down into the shaft," said Fairfax patrolman Roger Briney. "He was stuck for about three hours and passed out. He didn't even pick the right building. He was above the business office and his friends just left him there."

The maintenance man couldn't pull the stuck youth out of the shaft. Neither could police. It took the rescue squad 45 minutes to free him by cutting the duct open with an air chisel.

Jailed under $2,500 bond on a charge of attempted burglary was Timothy Lee Carathan, 18, of Bristow, Va., police said.