Thank you.

You know they sell smoke detector tester right? Its safer and easier, this method of testing can damage the sensor. Well thats what I've heard anyway. Just for future reference I guess. Anyway good video.

There is no need to connect the third unit with the second unit and the first unit. Once the first and second unit is connected and the third unit is connected to the second unit it automatically detects all three of them. Also you did not test the Carbon Monoxide unit, as in you did not see if there was a reading in the window.

Should never test with actual smoke