1997 Volvo 850 Could an escaping chemical cause drowsiness

Interior problem
1997 Volvo 850 Two Wheel Drive Automatic 97,000 miles

Ever since my car was transported from San Francisco to Baltimore, I have had the following serious problem: I am unable to drive mostly long and sometimes short distances without the feeling that my eyes want to close while driving. The driving is 90% on a highway (attempts to drive from Baltimore to NY) and even if I am well rested - and it is 7am in the morning, after 20 minutes, I need to fight the urge for my eyes to close. Frequently the air conditioning is on when this happens.

I rented a car a year ago (Prius) and drove for more than 4 1/2 hours on the West Coast, on highways and single lane roads without a problem.

Several people have suggested that there might be a leak of some type of chemical.

Any ideas? Many thanks.