"bag method" to analyze gas

Anyone familiar with the "bag method" or seen it demonstrated?

Saw it mentioned on the Oxycheq web site as a way to save money...

http://oxycheq.com/accessories.html

Sensor Tee: This is a "tee" used to hold the R17MED in place when using an oxygen analyzer. Price: $8 and shipping and handling. You could also use the "bag method" to analyze gas and save the $$$. Item: ROA-13

Have an empty plastic bag. Fill the bag with with the gas to be tested. Throw the sensor in the bag and wait. I've heard it described, but haven't seen it in action.

I'd spend the $8 and not have to worry about whether or not you mixed in some air with the gas to be tested. OTOH, when you are using any sort of flow method, you need to account for any increase in pressure of the gas being measured. The sensor is really a partial PRESSURE O2 sensor, not a % or fraction O2 sensor.