A study done several years ago suggests that 60% of carbon monoxide alarms sounding is due to an automobile in an attached garage.

By in large internal combustion engines produce thousands of parts per million carbon monoxide, particularly on start up.

As a demonstration look at the readings on Bacharach's single gas analyzer (the Monoxor II).  The instrument was placed in a garage, with the garage door open throughout the entire sequence of photos.

Before pulling a car in the garage, the instrument is on the right hand side, on a workbench approximately two feet from the door.

Within approximately 15 seconds the reading is 320 ppm's carbon monoxide.

Fifteen seconds later, the reading is 612 ppm's

After another 15 seconds, the reading is approaching 1,000 ppm's

Now lets take a look at how CO from exhaust fumes can enter into the home.

How many places do you see for exhaust fumes to get into this home?

Obvious possibilities include (but are not limited to):

	The two doors to the interior
	The joist cavities above the block wall to the right
	The hole where the metal return air and insulated supply go through the basement wall.

Of greater importance is the return trunk line running below the middle of the garage ceiling.

The smoke generator in this photo shows how leakage in the return trunk would be capable of sucking in any exhaust from a car.

Here the smoke generator identified additional leakage and one of the joints in the return trunk.

Also, consider other things we keep in our garages which we don't want to pull into the home such as:

	Gasoline
	Herbicides
	Pesticides
	Paint
	Paint thinner
	Etc, etc, etc.

Leakage in the return duct system also represents an efficiency concern.

Note how smoke from the smoke generator is drawn under the garage door (while the furnace blower, bathroom/kitchen exhaust fan or clothes dryer is in operation.  During the heating season, cold dry air is pulled into the home while during the cooling season, hot and possibly humid air pulled in increases air conditioning costs as well as decreasing comfort.

Several studies have found that leaky duct systems increase home heating and cooling costs by almost 20%!!