Most of us know that carbon monoxide gas (CO) is present in engine exhaust, and we have enough sense not to let an engine run in a closed garage.   But safety experts have suspected for years that carbon monoxide contributes to many more vehicle accidents than we're above to prove.   This insidious gas is colorless, odorless, tasteless and non-irritating.   It can kill without ever being detected by the senses.   When you smell exhaust fumes, you don't smell the carbon monoxide -- you smell unburned hydrocarbons.

Here are some points to help you keep the silent killer from making you one of its victims:

1. Be sure all parts of the manifold, exhaust pipe and muffler are sealed against leaks.

2. Keep your engine properly tuned so that combustion will be as complete as possible.

3. Before starting your engine, open the garage doors wide or, if you have an exhaust ventilating system, be sure it's operating.

4. Never crawl under your vehicle while the engine is running.   (There are many other good reasons for this)

5. Never drive without a fresh air supply coming into your vehicle.

6. Avoid following other vehicles too closely, their exhausts contain CO that can be drawn into your vehicle.

7. If you feel a little sleepy while driving, or feel a tightness across your forehead, or get a headache, or your temples start throbbing, you may be inhaling some carbon monoxide.   Other signs while driving at night are that the oncoming lights seem brighter and more glaring than usual and you are slower in recovering your vision from the glare, or that the darkness seems blacker than usual.   If you notice any of these signs, STOP at once, get out and walk about in the open air, and then drive with the windows open.

CO can slow down your brain and your reflexes, dim your vision and lead you into an accident.   During the cooler months we're more apt to drive with all the windows closed.   Always have some fresh air coming in.   The oxygen in fresh air is what you need more than anything else to offset the CO.

Most people don't realize how little CO it takes to be poisonous to the human body.   Only 50 parts of CO per million parts of air, by volume, is considered dangerous.   And there have been cases where that much of the deadly gas has been found in underpasses on city streets.   Carbon monoxide doesn't suffocate you, it kills you by chemical action.   It's an asphyxiant.   It combines directly with the blood in your body so the bloody can't carry oxygen to the tissues.   In a sense, you die from oxygen starvation.   So, if you have even the least suspicion you're inhaling too much CO, get some fresh air as fast as you can.

Protect Your Family and Yourself from Carbon Monoxide Poisoning (EPA)

NIOSH Pocket Guide to Chemical Hazards - Carbon Monoxide